+++ /dev/null
-/*
- * ring_buffer_frontend.c
- *
- * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; only
- * version 2.1 of the License.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- *
- * Ring buffer wait-free buffer synchronization. Producer-consumer and flight
- * recorder (overwrite) modes. See thesis:
- *
- * Desnoyers, Mathieu (2009), "Low-Impact Operating System Tracing", Ph.D.
- * dissertation, Ecole Polytechnique de Montreal.
- * http://www.lttng.org/pub/thesis/desnoyers-dissertation-2009-12.pdf
- *
- * - Algorithm presentation in Chapter 5:
- * "Lockless Multi-Core High-Throughput Buffering".
- * - Algorithm formal verification in Section 8.6:
- * "Formal verification of LTTng"
- *
- * Author:
- * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * Inspired from LTT and RelayFS:
- * Karim Yaghmour <karim@opersys.com>
- * Tom Zanussi <zanussi@us.ibm.com>
- * Bob Wisniewski <bob@watson.ibm.com>
- * And from K42 :
- * Bob Wisniewski <bob@watson.ibm.com>
- *
- * Buffer reader semantic :
- *
- * - get_subbuf_size
- * while buffer is not finalized and empty
- * - get_subbuf
- * - if return value != 0, continue
- * - splice one subbuffer worth of data to a pipe
- * - splice the data from pipe to disk/network
- * - put_subbuf
- */
-
-#define _GNU_SOURCE
-#define _LGPL_SOURCE
-#include <sys/types.h>
-#include <sys/mman.h>
-#include <sys/stat.h>
-#include <unistd.h>
-#include <fcntl.h>
-#include <signal.h>
-#include <time.h>
-#include <stdbool.h>
-#include <stdint.h>
-#include <urcu/compiler.h>
-#include <urcu/ref.h>
-#include <urcu/tls-compat.h>
-#include <poll.h>
-#include <helper.h>
-
-#include "smp.h"
-#include <lttng/ringbuffer-config.h>
-#include "vatomic.h"
-#include "backend.h"
-#include "frontend.h"
-#include "shm.h"
-#include "rb-init.h"
-#include "../liblttng-ust/compat.h" /* For ENODATA */
-
-/* Print DBG() messages about events lost only every 1048576 hits */
-#define DBG_PRINT_NR_LOST (1UL << 20)
-
-#define LTTNG_UST_RB_SIG_FLUSH SIGRTMIN
-#define LTTNG_UST_RB_SIG_READ SIGRTMIN + 1
-#define LTTNG_UST_RB_SIG_TEARDOWN SIGRTMIN + 2
-#define CLOCKID CLOCK_MONOTONIC
-#define LTTNG_UST_RING_BUFFER_GET_RETRY 10
-#define LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS 10
-#define RETRY_DELAY_MS 100 /* 100 ms. */
-
-/*
- * Non-static to ensure the compiler does not optimize away the xor.
- */
-uint8_t lttng_crash_magic_xor[] = RB_CRASH_DUMP_ABI_MAGIC_XOR;
-
-/*
- * Use POSIX SHM: shm_open(3) and shm_unlink(3).
- * close(2) to close the fd returned by shm_open.
- * shm_unlink releases the shared memory object name.
- * ftruncate(2) sets the size of the memory object.
- * mmap/munmap maps the shared memory obj to a virtual address in the
- * calling proceess (should be done both in libust and consumer).
- * See shm_overview(7) for details.
- * Pass file descriptor returned by shm_open(3) to ltt-sessiond through
- * a UNIX socket.
- *
- * Since we don't need to access the object using its name, we can
- * immediately shm_unlink(3) it, and only keep the handle with its file
- * descriptor.
- */
-
-/*
- * Internal structure representing offsets to use at a sub-buffer switch.
- */
-struct switch_offsets {
- unsigned long begin, end, old;
- size_t pre_header_padding, size;
- unsigned int switch_new_start:1, switch_new_end:1, switch_old_start:1,
- switch_old_end:1;
-};
-
-DEFINE_URCU_TLS(unsigned int, lib_ring_buffer_nesting);
-
-/*
- * wakeup_fd_mutex protects wakeup fd use by timer from concurrent
- * close.
- */
-static pthread_mutex_t wakeup_fd_mutex = PTHREAD_MUTEX_INITIALIZER;
-
-static
-void lib_ring_buffer_print_errors(struct channel *chan,
- struct lttng_ust_lib_ring_buffer *buf, int cpu,
- struct lttng_ust_shm_handle *handle);
-
-/*
- * Handle timer teardown race wrt memory free of private data by
- * ring buffer signals are handled by a single thread, which permits
- * a synchronization point between handling of each signal.
- * Protected by the lock within the structure.
- */
-struct timer_signal_data {
- pthread_t tid; /* thread id managing signals */
- int setup_done;
- int qs_done;
- pthread_mutex_t lock;
-};
-
-static struct timer_signal_data timer_signal = {
- .tid = 0,
- .setup_done = 0,
- .qs_done = 0,
- .lock = PTHREAD_MUTEX_INITIALIZER,
-};
-
-static bool lttng_ust_allow_blocking;
-
-void lttng_ust_ringbuffer_set_allow_blocking(void)
-{
- lttng_ust_allow_blocking = true;
-}
-
-/* Get blocking timeout, in ms */
-static int lttng_ust_ringbuffer_get_timeout(struct channel *chan)
-{
- if (!lttng_ust_allow_blocking)
- return 0;
- return chan->u.s.blocking_timeout_ms;
-}
-
-/**
- * lib_ring_buffer_reset - Reset ring buffer to initial values.
- * @buf: Ring buffer.
- *
- * Effectively empty the ring buffer. Should be called when the buffer is not
- * used for writing. The ring buffer can be opened for reading, but the reader
- * should not be using the iterator concurrently with reset. The previous
- * current iterator record is reset.
- */
-void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle)
-{
- struct channel *chan;
- const struct lttng_ust_lib_ring_buffer_config *config;
- unsigned int i;
-
- chan = shmp(handle, buf->backend.chan);
- if (!chan)
- return;
- config = &chan->backend.config;
- /*
- * Reset iterator first. It will put the subbuffer if it currently holds
- * it.
- */
- v_set(config, &buf->offset, 0);
- for (i = 0; i < chan->backend.num_subbuf; i++) {
- struct commit_counters_hot *cc_hot;
- struct commit_counters_cold *cc_cold;
- uint64_t *ts_end;
-
- cc_hot = shmp_index(handle, buf->commit_hot, i);
- if (!cc_hot)
- return;
- cc_cold = shmp_index(handle, buf->commit_cold, i);
- if (!cc_cold)
- return;
- ts_end = shmp_index(handle, buf->ts_end, i);
- if (!ts_end)
- return;
- v_set(config, &cc_hot->cc, 0);
- v_set(config, &cc_hot->seq, 0);
- v_set(config, &cc_cold->cc_sb, 0);
- *ts_end = 0;
- }
- uatomic_set(&buf->consumed, 0);
- uatomic_set(&buf->record_disabled, 0);
- v_set(config, &buf->last_tsc, 0);
- lib_ring_buffer_backend_reset(&buf->backend, handle);
- /* Don't reset number of active readers */
- v_set(config, &buf->records_lost_full, 0);
- v_set(config, &buf->records_lost_wrap, 0);
- v_set(config, &buf->records_lost_big, 0);
- v_set(config, &buf->records_count, 0);
- v_set(config, &buf->records_overrun, 0);
- buf->finalized = 0;
-}
-
-/**
- * channel_reset - Reset channel to initial values.
- * @chan: Channel.
- *
- * Effectively empty the channel. Should be called when the channel is not used
- * for writing. The channel can be opened for reading, but the reader should not
- * be using the iterator concurrently with reset. The previous current iterator
- * record is reset.
- */
-void channel_reset(struct channel *chan)
-{
- /*
- * Reset iterators first. Will put the subbuffer if held for reading.
- */
- uatomic_set(&chan->record_disabled, 0);
- /* Don't reset commit_count_mask, still valid */
- channel_backend_reset(&chan->backend);
- /* Don't reset switch/read timer interval */
- /* Don't reset notifiers and notifier enable bits */
- /* Don't reset reader reference count */
-}
-
-static
-void init_crash_abi(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_crash_abi *crash_abi,
- struct lttng_ust_lib_ring_buffer *buf,
- struct channel_backend *chanb,
- struct shm_object *shmobj,
- struct lttng_ust_shm_handle *handle)
-{
- int i;
-
- for (i = 0; i < RB_CRASH_DUMP_ABI_MAGIC_LEN; i++)
- crash_abi->magic[i] = lttng_crash_magic_xor[i] ^ 0xFF;
- crash_abi->mmap_length = shmobj->memory_map_size;
- crash_abi->endian = RB_CRASH_ENDIAN;
- crash_abi->major = RB_CRASH_DUMP_ABI_MAJOR;
- crash_abi->minor = RB_CRASH_DUMP_ABI_MINOR;
- crash_abi->word_size = sizeof(unsigned long);
- crash_abi->layout_type = LTTNG_CRASH_TYPE_UST;
-
- /* Offset of fields */
- crash_abi->offset.prod_offset =
- (uint32_t) ((char *) &buf->offset - (char *) buf);
- crash_abi->offset.consumed_offset =
- (uint32_t) ((char *) &buf->consumed - (char *) buf);
- crash_abi->offset.commit_hot_array =
- (uint32_t) ((char *) shmp(handle, buf->commit_hot) - (char *) buf);
- crash_abi->offset.commit_hot_seq =
- offsetof(struct commit_counters_hot, seq);
- crash_abi->offset.buf_wsb_array =
- (uint32_t) ((char *) shmp(handle, buf->backend.buf_wsb) - (char *) buf);
- crash_abi->offset.buf_wsb_id =
- offsetof(struct lttng_ust_lib_ring_buffer_backend_subbuffer, id);
- crash_abi->offset.sb_array =
- (uint32_t) ((char *) shmp(handle, buf->backend.array) - (char *) buf);
- crash_abi->offset.sb_array_shmp_offset =
- offsetof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp,
- shmp._ref.offset);
- crash_abi->offset.sb_backend_p_offset =
- offsetof(struct lttng_ust_lib_ring_buffer_backend_pages,
- p._ref.offset);
-
- /* Field length */
- crash_abi->length.prod_offset = sizeof(buf->offset);
- crash_abi->length.consumed_offset = sizeof(buf->consumed);
- crash_abi->length.commit_hot_seq =
- sizeof(((struct commit_counters_hot *) NULL)->seq);
- crash_abi->length.buf_wsb_id =
- sizeof(((struct lttng_ust_lib_ring_buffer_backend_subbuffer *) NULL)->id);
- crash_abi->length.sb_array_shmp_offset =
- sizeof(((struct lttng_ust_lib_ring_buffer_backend_pages_shmp *) NULL)->shmp._ref.offset);
- crash_abi->length.sb_backend_p_offset =
- sizeof(((struct lttng_ust_lib_ring_buffer_backend_pages *) NULL)->p._ref.offset);
-
- /* Array stride */
- crash_abi->stride.commit_hot_array =
- sizeof(struct commit_counters_hot);
- crash_abi->stride.buf_wsb_array =
- sizeof(struct lttng_ust_lib_ring_buffer_backend_subbuffer);
- crash_abi->stride.sb_array =
- sizeof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp);
-
- /* Buffer constants */
- crash_abi->buf_size = chanb->buf_size;
- crash_abi->subbuf_size = chanb->subbuf_size;
- crash_abi->num_subbuf = chanb->num_subbuf;
- crash_abi->mode = (uint32_t) chanb->config.mode;
-
- if (config->cb.content_size_field) {
- size_t offset, length;
-
- config->cb.content_size_field(config, &offset, &length);
- crash_abi->offset.content_size = offset;
- crash_abi->length.content_size = length;
- } else {
- crash_abi->offset.content_size = 0;
- crash_abi->length.content_size = 0;
- }
- if (config->cb.packet_size_field) {
- size_t offset, length;
-
- config->cb.packet_size_field(config, &offset, &length);
- crash_abi->offset.packet_size = offset;
- crash_abi->length.packet_size = length;
- } else {
- crash_abi->offset.packet_size = 0;
- crash_abi->length.packet_size = 0;
- }
-}
-
-/*
- * Must be called under cpu hotplug protection.
- */
-int lib_ring_buffer_create(struct lttng_ust_lib_ring_buffer *buf,
- struct channel_backend *chanb, int cpu,
- struct lttng_ust_shm_handle *handle,
- struct shm_object *shmobj)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
- struct channel *chan = caa_container_of(chanb, struct channel, backend);
- struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb;
- struct channel *shmp_chan;
- struct commit_counters_hot *cc_hot;
- void *priv = channel_get_private(chan);
- size_t subbuf_header_size;
- uint64_t tsc;
- int ret;
-
- /* Test for cpu hotplug */
- if (buf->backend.allocated)
- return 0;
-
- align_shm(shmobj, __alignof__(struct commit_counters_hot));
- set_shmp(buf->commit_hot,
- zalloc_shm(shmobj,
- sizeof(struct commit_counters_hot) * chan->backend.num_subbuf));
- if (!shmp(handle, buf->commit_hot)) {
- return -ENOMEM;
- }
-
- align_shm(shmobj, __alignof__(struct commit_counters_cold));
- set_shmp(buf->commit_cold,
- zalloc_shm(shmobj,
- sizeof(struct commit_counters_cold) * chan->backend.num_subbuf));
- if (!shmp(handle, buf->commit_cold)) {
- ret = -ENOMEM;
- goto free_commit;
- }
-
- align_shm(shmobj, __alignof__(uint64_t));
- set_shmp(buf->ts_end,
- zalloc_shm(shmobj,
- sizeof(uint64_t) * chan->backend.num_subbuf));
- if (!shmp(handle, buf->ts_end)) {
- ret = -ENOMEM;
- goto free_commit_cold;
- }
-
-
- ret = lib_ring_buffer_backend_create(&buf->backend, &chan->backend,
- cpu, handle, shmobj);
- if (ret) {
- goto free_init;
- }
-
- /*
- * Write the subbuffer header for first subbuffer so we know the total
- * duration of data gathering.
- */
- subbuf_header_size = config->cb.subbuffer_header_size();
- v_set(config, &buf->offset, subbuf_header_size);
- wsb = shmp_index(handle, buf->backend.buf_wsb, 0);
- if (!wsb) {
- ret = -EPERM;
- goto free_chanbuf;
- }
- subbuffer_id_clear_noref(config, &wsb->id);
- shmp_chan = shmp(handle, buf->backend.chan);
- if (!shmp_chan) {
- ret = -EPERM;
- goto free_chanbuf;
- }
- tsc = config->cb.ring_buffer_clock_read(shmp_chan);
- config->cb.buffer_begin(buf, tsc, 0, handle);
- cc_hot = shmp_index(handle, buf->commit_hot, 0);
- if (!cc_hot) {
- ret = -EPERM;
- goto free_chanbuf;
- }
- v_add(config, subbuf_header_size, &cc_hot->cc);
- v_add(config, subbuf_header_size, &cc_hot->seq);
-
- if (config->cb.buffer_create) {
- ret = config->cb.buffer_create(buf, priv, cpu, chanb->name, handle);
- if (ret)
- goto free_chanbuf;
- }
-
- init_crash_abi(config, &buf->crash_abi, buf, chanb, shmobj, handle);
-
- buf->backend.allocated = 1;
- return 0;
-
- /* Error handling */
-free_init:
- /* ts_end will be freed by shm teardown */
-free_commit_cold:
- /* commit_cold will be freed by shm teardown */
-free_commit:
- /* commit_hot will be freed by shm teardown */
-free_chanbuf:
- return ret;
-}
-
-static
-void lib_ring_buffer_channel_switch_timer(int sig, siginfo_t *si, void *uc)
-{
- const struct lttng_ust_lib_ring_buffer_config *config;
- struct lttng_ust_shm_handle *handle;
- struct channel *chan;
- int cpu;
-
- assert(CMM_LOAD_SHARED(timer_signal.tid) == pthread_self());
-
- chan = si->si_value.sival_ptr;
- handle = chan->handle;
- config = &chan->backend.config;
-
- DBG("Switch timer for channel %p\n", chan);
-
- /*
- * Only flush buffers periodically if readers are active.
- */
- pthread_mutex_lock(&wakeup_fd_mutex);
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
- for_each_possible_cpu(cpu) {
- struct lttng_ust_lib_ring_buffer *buf =
- shmp(handle, chan->backend.buf[cpu].shmp);
-
- if (!buf)
- goto end;
- if (uatomic_read(&buf->active_readers))
- lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE,
- chan->handle);
- }
- } else {
- struct lttng_ust_lib_ring_buffer *buf =
- shmp(handle, chan->backend.buf[0].shmp);
-
- if (!buf)
- goto end;
- if (uatomic_read(&buf->active_readers))
- lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE,
- chan->handle);
- }
-end:
- pthread_mutex_unlock(&wakeup_fd_mutex);
- return;
-}
-
-static
-int lib_ring_buffer_poll_deliver(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- struct lttng_ust_shm_handle *handle)
-{
- unsigned long consumed_old, consumed_idx, commit_count, write_offset;
- struct commit_counters_cold *cc_cold;
-
- consumed_old = uatomic_read(&buf->consumed);
- consumed_idx = subbuf_index(consumed_old, chan);
- cc_cold = shmp_index(handle, buf->commit_cold, consumed_idx);
- if (!cc_cold)
- return 0;
- commit_count = v_read(config, &cc_cold->cc_sb);
- /*
- * No memory barrier here, since we are only interested
- * in a statistically correct polling result. The next poll will
- * get the data is we are racing. The mb() that ensures correct
- * memory order is in get_subbuf.
- */
- write_offset = v_read(config, &buf->offset);
-
- /*
- * Check that the subbuffer we are trying to consume has been
- * already fully committed.
- */
-
- if (((commit_count - chan->backend.subbuf_size)
- & chan->commit_count_mask)
- - (buf_trunc(consumed_old, chan)
- >> chan->backend.num_subbuf_order)
- != 0)
- return 0;
-
- /*
- * Check that we are not about to read the same subbuffer in
- * which the writer head is.
- */
- if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed_old, chan)
- == 0)
- return 0;
-
- return 1;
-}
-
-static
-void lib_ring_buffer_wakeup(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle)
-{
- int wakeup_fd = shm_get_wakeup_fd(handle, &buf->self._ref);
- sigset_t sigpipe_set, pending_set, old_set;
- int ret, sigpipe_was_pending = 0;
-
- if (wakeup_fd < 0)
- return;
-
- /*
- * Wake-up the other end by writing a null byte in the pipe
- * (non-blocking). Important note: Because writing into the
- * pipe is non-blocking (and therefore we allow dropping wakeup
- * data, as long as there is wakeup data present in the pipe
- * buffer to wake up the consumer), the consumer should perform
- * the following sequence for waiting:
- * 1) empty the pipe (reads).
- * 2) check if there is data in the buffer.
- * 3) wait on the pipe (poll).
- *
- * Discard the SIGPIPE from write(), not disturbing any SIGPIPE
- * that might be already pending. If a bogus SIGPIPE is sent to
- * the entire process concurrently by a malicious user, it may
- * be simply discarded.
- */
- ret = sigemptyset(&pending_set);
- assert(!ret);
- /*
- * sigpending returns the mask of signals that are _both_
- * blocked for the thread _and_ pending for either the thread or
- * the entire process.
- */
- ret = sigpending(&pending_set);
- assert(!ret);
- sigpipe_was_pending = sigismember(&pending_set, SIGPIPE);
- /*
- * If sigpipe was pending, it means it was already blocked, so
- * no need to block it.
- */
- if (!sigpipe_was_pending) {
- ret = sigemptyset(&sigpipe_set);
- assert(!ret);
- ret = sigaddset(&sigpipe_set, SIGPIPE);
- assert(!ret);
- ret = pthread_sigmask(SIG_BLOCK, &sigpipe_set, &old_set);
- assert(!ret);
- }
- do {
- ret = write(wakeup_fd, "", 1);
- } while (ret == -1L && errno == EINTR);
- if (ret == -1L && errno == EPIPE && !sigpipe_was_pending) {
- struct timespec timeout = { 0, 0 };
- do {
- ret = sigtimedwait(&sigpipe_set, NULL,
- &timeout);
- } while (ret == -1L && errno == EINTR);
- }
- if (!sigpipe_was_pending) {
- ret = pthread_sigmask(SIG_SETMASK, &old_set, NULL);
- assert(!ret);
- }
-}
-
-static
-void lib_ring_buffer_channel_do_read(struct channel *chan)
-{
- const struct lttng_ust_lib_ring_buffer_config *config;
- struct lttng_ust_shm_handle *handle;
- int cpu;
-
- handle = chan->handle;
- config = &chan->backend.config;
-
- /*
- * Only flush buffers periodically if readers are active.
- */
- pthread_mutex_lock(&wakeup_fd_mutex);
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
- for_each_possible_cpu(cpu) {
- struct lttng_ust_lib_ring_buffer *buf =
- shmp(handle, chan->backend.buf[cpu].shmp);
-
- if (!buf)
- goto end;
- if (uatomic_read(&buf->active_readers)
- && lib_ring_buffer_poll_deliver(config, buf,
- chan, handle)) {
- lib_ring_buffer_wakeup(buf, handle);
- }
- }
- } else {
- struct lttng_ust_lib_ring_buffer *buf =
- shmp(handle, chan->backend.buf[0].shmp);
-
- if (!buf)
- goto end;
- if (uatomic_read(&buf->active_readers)
- && lib_ring_buffer_poll_deliver(config, buf,
- chan, handle)) {
- lib_ring_buffer_wakeup(buf, handle);
- }
- }
-end:
- pthread_mutex_unlock(&wakeup_fd_mutex);
-}
-
-static
-void lib_ring_buffer_channel_read_timer(int sig, siginfo_t *si, void *uc)
-{
- struct channel *chan;
-
- assert(CMM_LOAD_SHARED(timer_signal.tid) == pthread_self());
- chan = si->si_value.sival_ptr;
- DBG("Read timer for channel %p\n", chan);
- lib_ring_buffer_channel_do_read(chan);
- return;
-}
-
-static
-void rb_setmask(sigset_t *mask)
-{
- int ret;
-
- ret = sigemptyset(mask);
- if (ret) {
- PERROR("sigemptyset");
- }
- ret = sigaddset(mask, LTTNG_UST_RB_SIG_FLUSH);
- if (ret) {
- PERROR("sigaddset");
- }
- ret = sigaddset(mask, LTTNG_UST_RB_SIG_READ);
- if (ret) {
- PERROR("sigaddset");
- }
- ret = sigaddset(mask, LTTNG_UST_RB_SIG_TEARDOWN);
- if (ret) {
- PERROR("sigaddset");
- }
-}
-
-static
-void *sig_thread(void *arg)
-{
- sigset_t mask;
- siginfo_t info;
- int signr;
-
- /* Only self thread will receive signal mask. */
- rb_setmask(&mask);
- CMM_STORE_SHARED(timer_signal.tid, pthread_self());
-
- for (;;) {
- signr = sigwaitinfo(&mask, &info);
- if (signr == -1) {
- if (errno != EINTR)
- PERROR("sigwaitinfo");
- continue;
- }
- if (signr == LTTNG_UST_RB_SIG_FLUSH) {
- lib_ring_buffer_channel_switch_timer(info.si_signo,
- &info, NULL);
- } else if (signr == LTTNG_UST_RB_SIG_READ) {
- lib_ring_buffer_channel_read_timer(info.si_signo,
- &info, NULL);
- } else if (signr == LTTNG_UST_RB_SIG_TEARDOWN) {
- cmm_smp_mb();
- CMM_STORE_SHARED(timer_signal.qs_done, 1);
- cmm_smp_mb();
- } else {
- ERR("Unexptected signal %d\n", info.si_signo);
- }
- }
- return NULL;
-}
-
-/*
- * Ensure only a single thread listens on the timer signal.
- */
-static
-void lib_ring_buffer_setup_timer_thread(void)
-{
- pthread_t thread;
- int ret;
-
- pthread_mutex_lock(&timer_signal.lock);
- if (timer_signal.setup_done)
- goto end;
-
- ret = pthread_create(&thread, NULL, &sig_thread, NULL);
- if (ret) {
- errno = ret;
- PERROR("pthread_create");
- }
- ret = pthread_detach(thread);
- if (ret) {
- errno = ret;
- PERROR("pthread_detach");
- }
- timer_signal.setup_done = 1;
-end:
- pthread_mutex_unlock(&timer_signal.lock);
-}
-
-/*
- * Wait for signal-handling thread quiescent state.
- */
-static
-void lib_ring_buffer_wait_signal_thread_qs(unsigned int signr)
-{
- sigset_t pending_set;
- int ret;
-
- /*
- * We need to be the only thread interacting with the thread
- * that manages signals for teardown synchronization.
- */
- pthread_mutex_lock(&timer_signal.lock);
-
- /*
- * Ensure we don't have any signal queued for this channel.
- */
- for (;;) {
- ret = sigemptyset(&pending_set);
- if (ret == -1) {
- PERROR("sigemptyset");
- }
- ret = sigpending(&pending_set);
- if (ret == -1) {
- PERROR("sigpending");
- }
- if (!sigismember(&pending_set, signr))
- break;
- caa_cpu_relax();
- }
-
- /*
- * From this point, no new signal handler will be fired that
- * would try to access "chan". However, we still need to wait
- * for any currently executing handler to complete.
- */
- cmm_smp_mb();
- CMM_STORE_SHARED(timer_signal.qs_done, 0);
- cmm_smp_mb();
-
- /*
- * Kill with LTTNG_UST_RB_SIG_TEARDOWN, so signal management
- * thread wakes up.
- */
- kill(getpid(), LTTNG_UST_RB_SIG_TEARDOWN);
-
- while (!CMM_LOAD_SHARED(timer_signal.qs_done))
- caa_cpu_relax();
- cmm_smp_mb();
-
- pthread_mutex_unlock(&timer_signal.lock);
-}
-
-static
-void lib_ring_buffer_channel_switch_timer_start(struct channel *chan)
-{
- struct sigevent sev;
- struct itimerspec its;
- int ret;
-
- if (!chan->switch_timer_interval || chan->switch_timer_enabled)
- return;
-
- chan->switch_timer_enabled = 1;
-
- lib_ring_buffer_setup_timer_thread();
-
- sev.sigev_notify = SIGEV_SIGNAL;
- sev.sigev_signo = LTTNG_UST_RB_SIG_FLUSH;
- sev.sigev_value.sival_ptr = chan;
- ret = timer_create(CLOCKID, &sev, &chan->switch_timer);
- if (ret == -1) {
- PERROR("timer_create");
- }
-
- its.it_value.tv_sec = chan->switch_timer_interval / 1000000;
- its.it_value.tv_nsec = (chan->switch_timer_interval % 1000000) * 1000;
- its.it_interval.tv_sec = its.it_value.tv_sec;
- its.it_interval.tv_nsec = its.it_value.tv_nsec;
-
- ret = timer_settime(chan->switch_timer, 0, &its, NULL);
- if (ret == -1) {
- PERROR("timer_settime");
- }
-}
-
-static
-void lib_ring_buffer_channel_switch_timer_stop(struct channel *chan)
-{
- int ret;
-
- if (!chan->switch_timer_interval || !chan->switch_timer_enabled)
- return;
-
- ret = timer_delete(chan->switch_timer);
- if (ret == -1) {
- PERROR("timer_delete");
- }
-
- lib_ring_buffer_wait_signal_thread_qs(LTTNG_UST_RB_SIG_FLUSH);
-
- chan->switch_timer = 0;
- chan->switch_timer_enabled = 0;
-}
-
-static
-void lib_ring_buffer_channel_read_timer_start(struct channel *chan)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- struct sigevent sev;
- struct itimerspec its;
- int ret;
-
- if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER
- || !chan->read_timer_interval || chan->read_timer_enabled)
- return;
-
- chan->read_timer_enabled = 1;
-
- lib_ring_buffer_setup_timer_thread();
-
- sev.sigev_notify = SIGEV_SIGNAL;
- sev.sigev_signo = LTTNG_UST_RB_SIG_READ;
- sev.sigev_value.sival_ptr = chan;
- ret = timer_create(CLOCKID, &sev, &chan->read_timer);
- if (ret == -1) {
- PERROR("timer_create");
- }
-
- its.it_value.tv_sec = chan->read_timer_interval / 1000000;
- its.it_value.tv_nsec = (chan->read_timer_interval % 1000000) * 1000;
- its.it_interval.tv_sec = its.it_value.tv_sec;
- its.it_interval.tv_nsec = its.it_value.tv_nsec;
-
- ret = timer_settime(chan->read_timer, 0, &its, NULL);
- if (ret == -1) {
- PERROR("timer_settime");
- }
-}
-
-static
-void lib_ring_buffer_channel_read_timer_stop(struct channel *chan)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- int ret;
-
- if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER
- || !chan->read_timer_interval || !chan->read_timer_enabled)
- return;
-
- ret = timer_delete(chan->read_timer);
- if (ret == -1) {
- PERROR("timer_delete");
- }
-
- /*
- * do one more check to catch data that has been written in the last
- * timer period.
- */
- lib_ring_buffer_channel_do_read(chan);
-
- lib_ring_buffer_wait_signal_thread_qs(LTTNG_UST_RB_SIG_READ);
-
- chan->read_timer = 0;
- chan->read_timer_enabled = 0;
-}
-
-static void channel_unregister_notifiers(struct channel *chan,
- struct lttng_ust_shm_handle *handle)
-{
- lib_ring_buffer_channel_switch_timer_stop(chan);
- lib_ring_buffer_channel_read_timer_stop(chan);
-}
-
-static void channel_print_errors(struct channel *chan,
- struct lttng_ust_shm_handle *handle)
-{
- const struct lttng_ust_lib_ring_buffer_config *config =
- &chan->backend.config;
- int cpu;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
- for_each_possible_cpu(cpu) {
- struct lttng_ust_lib_ring_buffer *buf =
- shmp(handle, chan->backend.buf[cpu].shmp);
- if (buf)
- lib_ring_buffer_print_errors(chan, buf, cpu, handle);
- }
- } else {
- struct lttng_ust_lib_ring_buffer *buf =
- shmp(handle, chan->backend.buf[0].shmp);
-
- if (buf)
- lib_ring_buffer_print_errors(chan, buf, -1, handle);
- }
-}
-
-static void channel_free(struct channel *chan,
- struct lttng_ust_shm_handle *handle,
- int consumer)
-{
- channel_backend_free(&chan->backend, handle);
- /* chan is freed by shm teardown */
- shm_object_table_destroy(handle->table, consumer);
- free(handle);
-}
-
-/**
- * channel_create - Create channel.
- * @config: ring buffer instance configuration
- * @name: name of the channel
- * @priv_data: ring buffer client private data area pointer (output)
- * @priv_data_size: length, in bytes, of the private data area.
- * @priv_data_init: initialization data for private data.
- * @buf_addr: pointer the the beginning of the preallocated buffer contiguous
- * address mapping. It is used only by RING_BUFFER_STATIC
- * configuration. It can be set to NULL for other backends.
- * @subbuf_size: subbuffer size
- * @num_subbuf: number of subbuffers
- * @switch_timer_interval: Time interval (in us) to fill sub-buffers with
- * padding to let readers get those sub-buffers.
- * Used for live streaming.
- * @read_timer_interval: Time interval (in us) to wake up pending readers.
- * @stream_fds: array of stream file descriptors.
- * @nr_stream_fds: number of file descriptors in array.
- *
- * Holds cpu hotplug.
- * Returns NULL on failure.
- */
-struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
- const char *name,
- void **priv_data,
- size_t priv_data_align,
- size_t priv_data_size,
- void *priv_data_init,
- void *buf_addr, size_t subbuf_size,
- size_t num_subbuf, unsigned int switch_timer_interval,
- unsigned int read_timer_interval,
- const int *stream_fds, int nr_stream_fds,
- int64_t blocking_timeout)
-{
- int ret;
- size_t shmsize, chansize;
- struct channel *chan;
- struct lttng_ust_shm_handle *handle;
- struct shm_object *shmobj;
- unsigned int nr_streams;
- int64_t blocking_timeout_ms;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- nr_streams = num_possible_cpus();
- else
- nr_streams = 1;
-
- if (nr_stream_fds != nr_streams)
- return NULL;
-
- if (blocking_timeout < -1) {
- return NULL;
- }
- /* usec to msec */
- if (blocking_timeout == -1) {
- blocking_timeout_ms = -1;
- } else {
- blocking_timeout_ms = blocking_timeout / 1000;
- if (blocking_timeout_ms != (int32_t) blocking_timeout_ms) {
- return NULL;
- }
- }
-
- if (lib_ring_buffer_check_config(config, switch_timer_interval,
- read_timer_interval))
- return NULL;
-
- handle = zmalloc(sizeof(struct lttng_ust_shm_handle));
- if (!handle)
- return NULL;
-
- /* Allocate table for channel + per-cpu buffers */
- handle->table = shm_object_table_create(1 + num_possible_cpus());
- if (!handle->table)
- goto error_table_alloc;
-
- /* Calculate the shm allocation layout */
- shmsize = sizeof(struct channel);
- shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_shmp));
- shmsize += sizeof(struct lttng_ust_lib_ring_buffer_shmp) * nr_streams;
- chansize = shmsize;
- if (priv_data_align)
- shmsize += offset_align(shmsize, priv_data_align);
- shmsize += priv_data_size;
-
- /* Allocate normal memory for channel (not shared) */
- shmobj = shm_object_table_alloc(handle->table, shmsize, SHM_OBJECT_MEM,
- -1, -1);
- if (!shmobj)
- goto error_append;
- /* struct channel is at object 0, offset 0 (hardcoded) */
- set_shmp(handle->chan, zalloc_shm(shmobj, chansize));
- assert(handle->chan._ref.index == 0);
- assert(handle->chan._ref.offset == 0);
- chan = shmp(handle, handle->chan);
- if (!chan)
- goto error_append;
- chan->nr_streams = nr_streams;
-
- /* space for private data */
- if (priv_data_size) {
- DECLARE_SHMP(void, priv_data_alloc);
-
- align_shm(shmobj, priv_data_align);
- chan->priv_data_offset = shmobj->allocated_len;
- set_shmp(priv_data_alloc, zalloc_shm(shmobj, priv_data_size));
- if (!shmp(handle, priv_data_alloc))
- goto error_append;
- *priv_data = channel_get_private(chan);
- memcpy(*priv_data, priv_data_init, priv_data_size);
- } else {
- chan->priv_data_offset = -1;
- if (priv_data)
- *priv_data = NULL;
- }
-
- chan->u.s.blocking_timeout_ms = (int32_t) blocking_timeout_ms;
-
- ret = channel_backend_init(&chan->backend, name, config,
- subbuf_size, num_subbuf, handle,
- stream_fds);
- if (ret)
- goto error_backend_init;
-
- chan->handle = handle;
- chan->commit_count_mask = (~0UL >> chan->backend.num_subbuf_order);
-
- chan->switch_timer_interval = switch_timer_interval;
- chan->read_timer_interval = read_timer_interval;
- lib_ring_buffer_channel_switch_timer_start(chan);
- lib_ring_buffer_channel_read_timer_start(chan);
-
- return handle;
-
-error_backend_init:
-error_append:
- shm_object_table_destroy(handle->table, 1);
-error_table_alloc:
- free(handle);
- return NULL;
-}
-
-struct lttng_ust_shm_handle *channel_handle_create(void *data,
- uint64_t memory_map_size,
- int wakeup_fd)
-{
- struct lttng_ust_shm_handle *handle;
- struct shm_object *object;
-
- handle = zmalloc(sizeof(struct lttng_ust_shm_handle));
- if (!handle)
- return NULL;
-
- /* Allocate table for channel + per-cpu buffers */
- handle->table = shm_object_table_create(1 + num_possible_cpus());
- if (!handle->table)
- goto error_table_alloc;
- /* Add channel object */
- object = shm_object_table_append_mem(handle->table, data,
- memory_map_size, wakeup_fd);
- if (!object)
- goto error_table_object;
- /* struct channel is at object 0, offset 0 (hardcoded) */
- handle->chan._ref.index = 0;
- handle->chan._ref.offset = 0;
- return handle;
-
-error_table_object:
- shm_object_table_destroy(handle->table, 0);
-error_table_alloc:
- free(handle);
- return NULL;
-}
-
-int channel_handle_add_stream(struct lttng_ust_shm_handle *handle,
- int shm_fd, int wakeup_fd, uint32_t stream_nr,
- uint64_t memory_map_size)
-{
- struct shm_object *object;
-
- /* Add stream object */
- object = shm_object_table_append_shm(handle->table,
- shm_fd, wakeup_fd, stream_nr,
- memory_map_size);
- if (!object)
- return -EINVAL;
- return 0;
-}
-
-unsigned int channel_handle_get_nr_streams(struct lttng_ust_shm_handle *handle)
-{
- assert(handle->table);
- return handle->table->allocated_len - 1;
-}
-
-static
-void channel_release(struct channel *chan, struct lttng_ust_shm_handle *handle,
- int consumer)
-{
- channel_free(chan, handle, consumer);
-}
-
-/**
- * channel_destroy - Finalize, wait for q.s. and destroy channel.
- * @chan: channel to destroy
- *
- * Holds cpu hotplug.
- * Call "destroy" callback, finalize channels, decrement the channel
- * reference count. Note that when readers have completed data
- * consumption of finalized channels, get_subbuf() will return -ENODATA.
- * They should release their handle at that point.
- */
-void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
- int consumer)
-{
- if (consumer) {
- /*
- * Note: the consumer takes care of finalizing and
- * switching the buffers.
- */
- channel_unregister_notifiers(chan, handle);
- /*
- * The consumer prints errors.
- */
- channel_print_errors(chan, handle);
- }
-
- /*
- * sessiond/consumer are keeping a reference on the shm file
- * descriptor directly. No need to refcount.
- */
- channel_release(chan, handle, consumer);
- return;
-}
-
-struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
- const struct lttng_ust_lib_ring_buffer_config *config,
- struct channel *chan, int cpu,
- struct lttng_ust_shm_handle *handle,
- int *shm_fd, int *wait_fd,
- int *wakeup_fd,
- uint64_t *memory_map_size)
-{
- struct shm_ref *ref;
-
- if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
- cpu = 0;
- } else {
- if (cpu >= num_possible_cpus())
- return NULL;
- }
- ref = &chan->backend.buf[cpu].shmp._ref;
- *shm_fd = shm_get_shm_fd(handle, ref);
- *wait_fd = shm_get_wait_fd(handle, ref);
- *wakeup_fd = shm_get_wakeup_fd(handle, ref);
- if (shm_get_shm_size(handle, ref, memory_map_size))
- return NULL;
- return shmp(handle, chan->backend.buf[cpu].shmp);
-}
-
-int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
- struct channel *chan,
- struct lttng_ust_shm_handle *handle)
-{
- struct shm_ref *ref;
-
- ref = &handle->chan._ref;
- return shm_close_wait_fd(handle, ref);
-}
-
-int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
- struct channel *chan,
- struct lttng_ust_shm_handle *handle)
-{
- struct shm_ref *ref;
-
- ref = &handle->chan._ref;
- return shm_close_wakeup_fd(handle, ref);
-}
-
-int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
- struct channel *chan,
- struct lttng_ust_shm_handle *handle,
- int cpu)
-{
- struct shm_ref *ref;
-
- if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
- cpu = 0;
- } else {
- if (cpu >= num_possible_cpus())
- return -EINVAL;
- }
- ref = &chan->backend.buf[cpu].shmp._ref;
- return shm_close_wait_fd(handle, ref);
-}
-
-int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
- struct channel *chan,
- struct lttng_ust_shm_handle *handle,
- int cpu)
-{
- struct shm_ref *ref;
- int ret;
-
- if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
- cpu = 0;
- } else {
- if (cpu >= num_possible_cpus())
- return -EINVAL;
- }
- ref = &chan->backend.buf[cpu].shmp._ref;
- pthread_mutex_lock(&wakeup_fd_mutex);
- ret = shm_close_wakeup_fd(handle, ref);
- pthread_mutex_unlock(&wakeup_fd_mutex);
- return ret;
-}
-
-int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle)
-{
- if (uatomic_cmpxchg(&buf->active_readers, 0, 1) != 0)
- return -EBUSY;
- cmm_smp_mb();
- return 0;
-}
-
-void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle)
-{
- struct channel *chan = shmp(handle, buf->backend.chan);
-
- if (!chan)
- return;
- CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1);
- cmm_smp_mb();
- uatomic_dec(&buf->active_readers);
-}
-
-/**
- * lib_ring_buffer_snapshot - save subbuffer position snapshot (for read)
- * @buf: ring buffer
- * @consumed: consumed count indicating the position where to read
- * @produced: produced count, indicates position when to stop reading
- *
- * Returns -ENODATA if buffer is finalized, -EAGAIN if there is currently no
- * data to read at consumed position, or 0 if the get operation succeeds.
- */
-
-int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
- unsigned long *consumed, unsigned long *produced,
- struct lttng_ust_shm_handle *handle)
-{
- struct channel *chan;
- const struct lttng_ust_lib_ring_buffer_config *config;
- unsigned long consumed_cur, write_offset;
- int finalized;
-
- chan = shmp(handle, buf->backend.chan);
- if (!chan)
- return -EPERM;
- config = &chan->backend.config;
- finalized = CMM_ACCESS_ONCE(buf->finalized);
- /*
- * Read finalized before counters.
- */
- cmm_smp_rmb();
- consumed_cur = uatomic_read(&buf->consumed);
- /*
- * No need to issue a memory barrier between consumed count read and
- * write offset read, because consumed count can only change
- * concurrently in overwrite mode, and we keep a sequence counter
- * identifier derived from the write offset to check we are getting
- * the same sub-buffer we are expecting (the sub-buffers are atomically
- * "tagged" upon writes, tags are checked upon read).
- */
- write_offset = v_read(config, &buf->offset);
-
- /*
- * Check that we are not about to read the same subbuffer in
- * which the writer head is.
- */
- if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed_cur, chan)
- == 0)
- goto nodata;
-
- *consumed = consumed_cur;
- *produced = subbuf_trunc(write_offset, chan);
-
- return 0;
-
-nodata:
- /*
- * The memory barriers __wait_event()/wake_up_interruptible() take care
- * of "raw_spin_is_locked" memory ordering.
- */
- if (finalized)
- return -ENODATA;
- else
- return -EAGAIN;
-}
-
-/**
- * Performs the same function as lib_ring_buffer_snapshot(), but the positions
- * are saved regardless of whether the consumed and produced positions are
- * in the same subbuffer.
- * @buf: ring buffer
- * @consumed: consumed byte count indicating the last position read
- * @produced: produced byte count indicating the last position written
- *
- * This function is meant to provide information on the exact producer and
- * consumer positions without regard for the "snapshot" feature.
- */
-int lib_ring_buffer_snapshot_sample_positions(
- struct lttng_ust_lib_ring_buffer *buf,
- unsigned long *consumed, unsigned long *produced,
- struct lttng_ust_shm_handle *handle)
-{
- struct channel *chan;
- const struct lttng_ust_lib_ring_buffer_config *config;
-
- chan = shmp(handle, buf->backend.chan);
- if (!chan)
- return -EPERM;
- config = &chan->backend.config;
- cmm_smp_rmb();
- *consumed = uatomic_read(&buf->consumed);
- /*
- * No need to issue a memory barrier between consumed count read and
- * write offset read, because consumed count can only change
- * concurrently in overwrite mode, and we keep a sequence counter
- * identifier derived from the write offset to check we are getting
- * the same sub-buffer we are expecting (the sub-buffers are atomically
- * "tagged" upon writes, tags are checked upon read).
- */
- *produced = v_read(config, &buf->offset);
- return 0;
-}
-
-/**
- * lib_ring_buffer_move_consumer - move consumed counter forward
- * @buf: ring buffer
- * @consumed_new: new consumed count value
- */
-void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
- unsigned long consumed_new,
- struct lttng_ust_shm_handle *handle)
-{
- struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend;
- struct channel *chan;
- unsigned long consumed;
-
- chan = shmp(handle, bufb->chan);
- if (!chan)
- return;
- CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1);
-
- /*
- * Only push the consumed value forward.
- * If the consumed cmpxchg fails, this is because we have been pushed by
- * the writer in flight recorder mode.
- */
- consumed = uatomic_read(&buf->consumed);
- while ((long) consumed - (long) consumed_new < 0)
- consumed = uatomic_cmpxchg(&buf->consumed, consumed,
- consumed_new);
-}
-
-/**
- * lib_ring_buffer_get_subbuf - get exclusive access to subbuffer for reading
- * @buf: ring buffer
- * @consumed: consumed count indicating the position where to read
- *
- * Returns -ENODATA if buffer is finalized, -EAGAIN if there is currently no
- * data to read at consumed position, or 0 if the get operation succeeds.
- */
-int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
- unsigned long consumed,
- struct lttng_ust_shm_handle *handle)
-{
- struct channel *chan;
- const struct lttng_ust_lib_ring_buffer_config *config;
- unsigned long consumed_cur, consumed_idx, commit_count, write_offset;
- int ret, finalized, nr_retry = LTTNG_UST_RING_BUFFER_GET_RETRY;
- struct commit_counters_cold *cc_cold;
-
- chan = shmp(handle, buf->backend.chan);
- if (!chan)
- return -EPERM;
- config = &chan->backend.config;
-retry:
- finalized = CMM_ACCESS_ONCE(buf->finalized);
- /*
- * Read finalized before counters.
- */
- cmm_smp_rmb();
- consumed_cur = uatomic_read(&buf->consumed);
- consumed_idx = subbuf_index(consumed, chan);
- cc_cold = shmp_index(handle, buf->commit_cold, consumed_idx);
- if (!cc_cold)
- return -EPERM;
- commit_count = v_read(config, &cc_cold->cc_sb);
- /*
- * Make sure we read the commit count before reading the buffer
- * data and the write offset. Correct consumed offset ordering
- * wrt commit count is insured by the use of cmpxchg to update
- * the consumed offset.
- */
- /*
- * Local rmb to match the remote wmb to read the commit count
- * before the buffer data and the write offset.
- */
- cmm_smp_rmb();
-
- write_offset = v_read(config, &buf->offset);
-
- /*
- * Check that the buffer we are getting is after or at consumed_cur
- * position.
- */
- if ((long) subbuf_trunc(consumed, chan)
- - (long) subbuf_trunc(consumed_cur, chan) < 0)
- goto nodata;
-
- /*
- * Check that the subbuffer we are trying to consume has been
- * already fully committed. There are a few causes that can make
- * this unavailability situation occur:
- *
- * Temporary (short-term) situation:
- * - Application is running on a different CPU, between reserve
- * and commit ring buffer operations,
- * - Application is preempted between reserve and commit ring
- * buffer operations,
- *
- * Long-term situation:
- * - Application is stopped (SIGSTOP) between reserve and commit
- * ring buffer operations. Could eventually be resumed by
- * SIGCONT.
- * - Application is killed (SIGTERM, SIGINT, SIGKILL) between
- * reserve and commit ring buffer operation.
- *
- * From a consumer perspective, handling short-term
- * unavailability situations is performed by retrying a few
- * times after a delay. Handling long-term unavailability
- * situations is handled by failing to get the sub-buffer.
- *
- * In all of those situations, if the application is taking a
- * long time to perform its commit after ring buffer space
- * reservation, we can end up in a situation where the producer
- * will fill the ring buffer and try to write into the same
- * sub-buffer again (which has a missing commit). This is
- * handled by the producer in the sub-buffer switch handling
- * code of the reserve routine by detecting unbalanced
- * reserve/commit counters and discarding all further events
- * until the situation is resolved in those situations. Two
- * scenarios can occur:
- *
- * 1) The application causing the reserve/commit counters to be
- * unbalanced has been terminated. In this situation, all
- * further events will be discarded in the buffers, and no
- * further buffer data will be readable by the consumer
- * daemon. Tearing down the UST tracing session and starting
- * anew is a work-around for those situations. Note that this
- * only affects per-UID tracing. In per-PID tracing, the
- * application vanishes with the termination, and therefore
- * no more data needs to be written to the buffers.
- * 2) The application causing the unbalance has been delayed for
- * a long time, but will eventually try to increment the
- * commit counter after eventually writing to the sub-buffer.
- * This situation can cause events to be discarded until the
- * application resumes its operations.
- */
- if (((commit_count - chan->backend.subbuf_size)
- & chan->commit_count_mask)
- - (buf_trunc(consumed, chan)
- >> chan->backend.num_subbuf_order)
- != 0) {
- if (nr_retry-- > 0) {
- if (nr_retry <= (LTTNG_UST_RING_BUFFER_GET_RETRY >> 1))
- (void) poll(NULL, 0, LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS);
- goto retry;
- } else {
- goto nodata;
- }
- }
-
- /*
- * Check that we are not about to read the same subbuffer in
- * which the writer head is.
- */
- if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed, chan)
- == 0)
- goto nodata;
-
- /*
- * Failure to get the subbuffer causes a busy-loop retry without going
- * to a wait queue. These are caused by short-lived race windows where
- * the writer is getting access to a subbuffer we were trying to get
- * access to. Also checks that the "consumed" buffer count we are
- * looking for matches the one contained in the subbuffer id.
- *
- * The short-lived race window described here can be affected by
- * application signals and preemption, thus requiring to bound
- * the loop to a maximum number of retry.
- */
- ret = update_read_sb_index(config, &buf->backend, &chan->backend,
- consumed_idx, buf_trunc_val(consumed, chan),
- handle);
- if (ret) {
- if (nr_retry-- > 0) {
- if (nr_retry <= (LTTNG_UST_RING_BUFFER_GET_RETRY >> 1))
- (void) poll(NULL, 0, LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS);
- goto retry;
- } else {
- goto nodata;
- }
- }
- subbuffer_id_clear_noref(config, &buf->backend.buf_rsb.id);
-
- buf->get_subbuf_consumed = consumed;
- buf->get_subbuf = 1;
-
- return 0;
-
-nodata:
- /*
- * The memory barriers __wait_event()/wake_up_interruptible() take care
- * of "raw_spin_is_locked" memory ordering.
- */
- if (finalized)
- return -ENODATA;
- else
- return -EAGAIN;
-}
-
-/**
- * lib_ring_buffer_put_subbuf - release exclusive subbuffer access
- * @buf: ring buffer
- */
-void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle)
-{
- struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend;
- struct channel *chan;
- const struct lttng_ust_lib_ring_buffer_config *config;
- unsigned long sb_bindex, consumed_idx, consumed;
- struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
- struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
-
- chan = shmp(handle, bufb->chan);
- if (!chan)
- return;
- config = &chan->backend.config;
- CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1);
-
- if (!buf->get_subbuf) {
- /*
- * Reader puts a subbuffer it did not get.
- */
- CHAN_WARN_ON(chan, 1);
- return;
- }
- consumed = buf->get_subbuf_consumed;
- buf->get_subbuf = 0;
-
- /*
- * Clear the records_unread counter. (overruns counter)
- * Can still be non-zero if a file reader simply grabbed the data
- * without using iterators.
- * Can be below zero if an iterator is used on a snapshot more than
- * once.
- */
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
- rpages = shmp_index(handle, bufb->array, sb_bindex);
- if (!rpages)
- return;
- backend_pages = shmp(handle, rpages->shmp);
- if (!backend_pages)
- return;
- v_add(config, v_read(config, &backend_pages->records_unread),
- &bufb->records_read);
- v_set(config, &backend_pages->records_unread, 0);
- CHAN_WARN_ON(chan, config->mode == RING_BUFFER_OVERWRITE
- && subbuffer_id_is_noref(config, bufb->buf_rsb.id));
- subbuffer_id_set_noref(config, &bufb->buf_rsb.id);
-
- /*
- * Exchange the reader subbuffer with the one we put in its place in the
- * writer subbuffer table. Expect the original consumed count. If
- * update_read_sb_index fails, this is because the writer updated the
- * subbuffer concurrently. We should therefore keep the subbuffer we
- * currently have: it has become invalid to try reading this sub-buffer
- * consumed count value anyway.
- */
- consumed_idx = subbuf_index(consumed, chan);
- update_read_sb_index(config, &buf->backend, &chan->backend,
- consumed_idx, buf_trunc_val(consumed, chan),
- handle);
- /*
- * update_read_sb_index return value ignored. Don't exchange sub-buffer
- * if the writer concurrently updated it.
- */
-}
-
-/*
- * cons_offset is an iterator on all subbuffer offsets between the reader
- * position and the writer position. (inclusive)
- */
-static
-void lib_ring_buffer_print_subbuffer_errors(struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- unsigned long cons_offset,
- int cpu,
- struct lttng_ust_shm_handle *handle)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long cons_idx, commit_count, commit_count_sb;
- struct commit_counters_hot *cc_hot;
- struct commit_counters_cold *cc_cold;
-
- cons_idx = subbuf_index(cons_offset, chan);
- cc_hot = shmp_index(handle, buf->commit_hot, cons_idx);
- if (!cc_hot)
- return;
- cc_cold = shmp_index(handle, buf->commit_cold, cons_idx);
- if (!cc_cold)
- return;
- commit_count = v_read(config, &cc_hot->cc);
- commit_count_sb = v_read(config, &cc_cold->cc_sb);
-
- if (subbuf_offset(commit_count, chan) != 0)
- DBG("ring buffer %s, cpu %d: "
- "commit count in subbuffer %lu,\n"
- "expecting multiples of %lu bytes\n"
- " [ %lu bytes committed, %lu bytes reader-visible ]\n",
- chan->backend.name, cpu, cons_idx,
- chan->backend.subbuf_size,
- commit_count, commit_count_sb);
-
- DBG("ring buffer: %s, cpu %d: %lu bytes committed\n",
- chan->backend.name, cpu, commit_count);
-}
-
-static
-void lib_ring_buffer_print_buffer_errors(struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- void *priv, int cpu,
- struct lttng_ust_shm_handle *handle)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long write_offset, cons_offset;
-
- /*
- * No need to order commit_count, write_offset and cons_offset reads
- * because we execute at teardown when no more writer nor reader
- * references are left.
- */
- write_offset = v_read(config, &buf->offset);
- cons_offset = uatomic_read(&buf->consumed);
- if (write_offset != cons_offset)
- DBG("ring buffer %s, cpu %d: "
- "non-consumed data\n"
- " [ %lu bytes written, %lu bytes read ]\n",
- chan->backend.name, cpu, write_offset, cons_offset);
-
- for (cons_offset = uatomic_read(&buf->consumed);
- (long) (subbuf_trunc((unsigned long) v_read(config, &buf->offset),
- chan)
- - cons_offset) > 0;
- cons_offset = subbuf_align(cons_offset, chan))
- lib_ring_buffer_print_subbuffer_errors(buf, chan, cons_offset,
- cpu, handle);
-}
-
-static
-void lib_ring_buffer_print_errors(struct channel *chan,
- struct lttng_ust_lib_ring_buffer *buf, int cpu,
- struct lttng_ust_shm_handle *handle)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- void *priv = channel_get_private(chan);
-
- if (!strcmp(chan->backend.name, "relay-metadata-mmap")) {
- DBG("ring buffer %s: %lu records written, "
- "%lu records overrun\n",
- chan->backend.name,
- v_read(config, &buf->records_count),
- v_read(config, &buf->records_overrun));
- } else {
- DBG("ring buffer %s, cpu %d: %lu records written, "
- "%lu records overrun\n",
- chan->backend.name, cpu,
- v_read(config, &buf->records_count),
- v_read(config, &buf->records_overrun));
-
- if (v_read(config, &buf->records_lost_full)
- || v_read(config, &buf->records_lost_wrap)
- || v_read(config, &buf->records_lost_big))
- DBG("ring buffer %s, cpu %d: records were lost. Caused by:\n"
- " [ %lu buffer full, %lu nest buffer wrap-around, "
- "%lu event too big ]\n",
- chan->backend.name, cpu,
- v_read(config, &buf->records_lost_full),
- v_read(config, &buf->records_lost_wrap),
- v_read(config, &buf->records_lost_big));
- }
- lib_ring_buffer_print_buffer_errors(buf, chan, priv, cpu, handle);
-}
-
-/*
- * lib_ring_buffer_switch_old_start: Populate old subbuffer header.
- *
- * Only executed by SWITCH_FLUSH, which can be issued while tracing is
- * active or at buffer finalization (destroy).
- */
-static
-void lib_ring_buffer_switch_old_start(struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- uint64_t tsc,
- struct lttng_ust_shm_handle *handle)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long oldidx = subbuf_index(offsets->old, chan);
- unsigned long commit_count;
- struct commit_counters_hot *cc_hot;
-
- config->cb.buffer_begin(buf, tsc, oldidx, handle);
-
- /*
- * Order all writes to buffer before the commit count update that will
- * determine that the subbuffer is full.
- */
- cmm_smp_wmb();
- cc_hot = shmp_index(handle, buf->commit_hot, oldidx);
- if (!cc_hot)
- return;
- v_add(config, config->cb.subbuffer_header_size(),
- &cc_hot->cc);
- commit_count = v_read(config, &cc_hot->cc);
- /* Check if the written buffer has to be delivered */
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->old,
- commit_count, oldidx, handle, tsc);
- lib_ring_buffer_write_commit_counter(config, buf, chan,
- offsets->old + config->cb.subbuffer_header_size(),
- commit_count, handle, cc_hot);
-}
-
-/*
- * lib_ring_buffer_switch_old_end: switch old subbuffer
- *
- * Note : offset_old should never be 0 here. It is ok, because we never perform
- * buffer switch on an empty subbuffer in SWITCH_ACTIVE mode. The caller
- * increments the offset_old value when doing a SWITCH_FLUSH on an empty
- * subbuffer.
- */
-static
-void lib_ring_buffer_switch_old_end(struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- uint64_t tsc,
- struct lttng_ust_shm_handle *handle)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long oldidx = subbuf_index(offsets->old - 1, chan);
- unsigned long commit_count, padding_size, data_size;
- struct commit_counters_hot *cc_hot;
- uint64_t *ts_end;
-
- data_size = subbuf_offset(offsets->old - 1, chan) + 1;
- padding_size = chan->backend.subbuf_size - data_size;
- subbuffer_set_data_size(config, &buf->backend, oldidx, data_size,
- handle);
-
- ts_end = shmp_index(handle, buf->ts_end, oldidx);
- if (!ts_end)
- return;
- /*
- * This is the last space reservation in that sub-buffer before
- * it gets delivered. This provides exclusive access to write to
- * this sub-buffer's ts_end. There are also no concurrent
- * readers of that ts_end because delivery of that sub-buffer is
- * postponed until the commit counter is incremented for the
- * current space reservation.
- */
- *ts_end = tsc;
-
- /*
- * Order all writes to buffer and store to ts_end before the commit
- * count update that will determine that the subbuffer is full.
- */
- cmm_smp_wmb();
- cc_hot = shmp_index(handle, buf->commit_hot, oldidx);
- if (!cc_hot)
- return;
- v_add(config, padding_size, &cc_hot->cc);
- commit_count = v_read(config, &cc_hot->cc);
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->old - 1,
- commit_count, oldidx, handle, tsc);
- lib_ring_buffer_write_commit_counter(config, buf, chan,
- offsets->old + padding_size, commit_count, handle,
- cc_hot);
-}
-
-/*
- * lib_ring_buffer_switch_new_start: Populate new subbuffer.
- *
- * This code can be executed unordered : writers may already have written to the
- * sub-buffer before this code gets executed, caution. The commit makes sure
- * that this code is executed before the deliver of this sub-buffer.
- */
-static
-void lib_ring_buffer_switch_new_start(struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- uint64_t tsc,
- struct lttng_ust_shm_handle *handle)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long beginidx = subbuf_index(offsets->begin, chan);
- unsigned long commit_count;
- struct commit_counters_hot *cc_hot;
-
- config->cb.buffer_begin(buf, tsc, beginidx, handle);
-
- /*
- * Order all writes to buffer before the commit count update that will
- * determine that the subbuffer is full.
- */
- cmm_smp_wmb();
- cc_hot = shmp_index(handle, buf->commit_hot, beginidx);
- if (!cc_hot)
- return;
- v_add(config, config->cb.subbuffer_header_size(), &cc_hot->cc);
- commit_count = v_read(config, &cc_hot->cc);
- /* Check if the written buffer has to be delivered */
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->begin,
- commit_count, beginidx, handle, tsc);
- lib_ring_buffer_write_commit_counter(config, buf, chan,
- offsets->begin + config->cb.subbuffer_header_size(),
- commit_count, handle, cc_hot);
-}
-
-/*
- * lib_ring_buffer_switch_new_end: finish switching current subbuffer
- *
- * Calls subbuffer_set_data_size() to set the data size of the current
- * sub-buffer. We do not need to perform check_deliver nor commit here,
- * since this task will be done by the "commit" of the event for which
- * we are currently doing the space reservation.
- */
-static
-void lib_ring_buffer_switch_new_end(struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- uint64_t tsc,
- struct lttng_ust_shm_handle *handle)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long endidx, data_size;
- uint64_t *ts_end;
-
- endidx = subbuf_index(offsets->end - 1, chan);
- data_size = subbuf_offset(offsets->end - 1, chan) + 1;
- subbuffer_set_data_size(config, &buf->backend, endidx, data_size,
- handle);
- ts_end = shmp_index(handle, buf->ts_end, endidx);
- if (!ts_end)
- return;
- /*
- * This is the last space reservation in that sub-buffer before
- * it gets delivered. This provides exclusive access to write to
- * this sub-buffer's ts_end. There are also no concurrent
- * readers of that ts_end because delivery of that sub-buffer is
- * postponed until the commit counter is incremented for the
- * current space reservation.
- */
- *ts_end = tsc;
-}
-
-/*
- * Returns :
- * 0 if ok
- * !0 if execution must be aborted.
- */
-static
-int lib_ring_buffer_try_switch_slow(enum switch_mode mode,
- struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- uint64_t *tsc,
- struct lttng_ust_shm_handle *handle)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long off, reserve_commit_diff;
-
- offsets->begin = v_read(config, &buf->offset);
- offsets->old = offsets->begin;
- offsets->switch_old_start = 0;
- off = subbuf_offset(offsets->begin, chan);
-
- *tsc = config->cb.ring_buffer_clock_read(chan);
-
- /*
- * Ensure we flush the header of an empty subbuffer when doing the
- * finalize (SWITCH_FLUSH). This ensures that we end up knowing the
- * total data gathering duration even if there were no records saved
- * after the last buffer switch.
- * In SWITCH_ACTIVE mode, switch the buffer when it contains events.
- * SWITCH_ACTIVE only flushes the current subbuffer, dealing with end of
- * subbuffer header as appropriate.
- * The next record that reserves space will be responsible for
- * populating the following subbuffer header. We choose not to populate
- * the next subbuffer header here because we want to be able to use
- * SWITCH_ACTIVE for periodical buffer flush, which must
- * guarantee that all the buffer content (records and header
- * timestamps) are visible to the reader. This is required for
- * quiescence guarantees for the fusion merge.
- */
- if (mode != SWITCH_FLUSH && !off)
- return -1; /* we do not have to switch : buffer is empty */
-
- if (caa_unlikely(off == 0)) {
- unsigned long sb_index, commit_count;
- struct commit_counters_cold *cc_cold;
-
- /*
- * We are performing a SWITCH_FLUSH. There may be concurrent
- * writes into the buffer if e.g. invoked while performing a
- * snapshot on an active trace.
- *
- * If the client does not save any header information
- * (sub-buffer header size == 0), don't switch empty subbuffer
- * on finalize, because it is invalid to deliver a completely
- * empty subbuffer.
- */
- if (!config->cb.subbuffer_header_size())
- return -1;
-
- /* Test new buffer integrity */
- sb_index = subbuf_index(offsets->begin, chan);
- cc_cold = shmp_index(handle, buf->commit_cold, sb_index);
- if (!cc_cold)
- return -1;
- commit_count = v_read(config, &cc_cold->cc_sb);
- reserve_commit_diff =
- (buf_trunc(offsets->begin, chan)
- >> chan->backend.num_subbuf_order)
- - (commit_count & chan->commit_count_mask);
- if (caa_likely(reserve_commit_diff == 0)) {
- /* Next subbuffer not being written to. */
- if (caa_unlikely(config->mode != RING_BUFFER_OVERWRITE &&
- subbuf_trunc(offsets->begin, chan)
- - subbuf_trunc((unsigned long)
- uatomic_read(&buf->consumed), chan)
- >= chan->backend.buf_size)) {
- /*
- * We do not overwrite non consumed buffers
- * and we are full : don't switch.
- */
- return -1;
- } else {
- /*
- * Next subbuffer not being written to, and we
- * are either in overwrite mode or the buffer is
- * not full. It's safe to write in this new
- * subbuffer.
- */
- }
- } else {
- /*
- * Next subbuffer reserve offset does not match the
- * commit offset. Don't perform switch in
- * producer-consumer and overwrite mode. Caused by
- * either a writer OOPS or too many nested writes over a
- * reserve/commit pair.
- */
- return -1;
- }
-
- /*
- * Need to write the subbuffer start header on finalize.
- */
- offsets->switch_old_start = 1;
- }
- offsets->begin = subbuf_align(offsets->begin, chan);
- /* Note: old points to the next subbuf at offset 0 */
- offsets->end = offsets->begin;
- return 0;
-}
-
-/*
- * Force a sub-buffer switch. This operation is completely reentrant : can be
- * called while tracing is active with absolutely no lock held.
- *
- * For RING_BUFFER_SYNC_PER_CPU ring buffers, as a v_cmpxchg is used for
- * some atomic operations, this function must be called from the CPU
- * which owns the buffer for a ACTIVE flush. However, for
- * RING_BUFFER_SYNC_GLOBAL ring buffers, this function can be called
- * from any CPU.
- */
-void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf, enum switch_mode mode,
- struct lttng_ust_shm_handle *handle)
-{
- struct channel *chan;
- const struct lttng_ust_lib_ring_buffer_config *config;
- struct switch_offsets offsets;
- unsigned long oldidx;
- uint64_t tsc;
-
- chan = shmp(handle, buf->backend.chan);
- if (!chan)
- return;
- config = &chan->backend.config;
-
- offsets.size = 0;
-
- /*
- * Perform retryable operations.
- */
- do {
- if (lib_ring_buffer_try_switch_slow(mode, buf, chan, &offsets,
- &tsc, handle))
- return; /* Switch not needed */
- } while (v_cmpxchg(config, &buf->offset, offsets.old, offsets.end)
- != offsets.old);
-
- /*
- * Atomically update last_tsc. This update races against concurrent
- * atomic updates, but the race will always cause supplementary full TSC
- * records, never the opposite (missing a full TSC record when it would
- * be needed).
- */
- save_last_tsc(config, buf, tsc);
-
- /*
- * Push the reader if necessary
- */
- lib_ring_buffer_reserve_push_reader(buf, chan, offsets.old);
-
- oldidx = subbuf_index(offsets.old, chan);
- lib_ring_buffer_clear_noref(config, &buf->backend, oldidx, handle);
-
- /*
- * May need to populate header start on SWITCH_FLUSH.
- */
- if (offsets.switch_old_start) {
- lib_ring_buffer_switch_old_start(buf, chan, &offsets, tsc, handle);
- offsets.old += config->cb.subbuffer_header_size();
- }
-
- /*
- * Switch old subbuffer.
- */
- lib_ring_buffer_switch_old_end(buf, chan, &offsets, tsc, handle);
-}
-
-static
-bool handle_blocking_retry(int *timeout_left_ms)
-{
- int timeout = *timeout_left_ms, delay;
-
- if (caa_likely(!timeout))
- return false; /* Do not retry, discard event. */
- if (timeout < 0) /* Wait forever. */
- delay = RETRY_DELAY_MS;
- else
- delay = min_t(int, timeout, RETRY_DELAY_MS);
- (void) poll(NULL, 0, delay);
- if (timeout > 0)
- *timeout_left_ms -= delay;
- return true; /* Retry. */
-}
-
-/*
- * Returns :
- * 0 if ok
- * -ENOSPC if event size is too large for packet.
- * -ENOBUFS if there is currently not enough space in buffer for the event.
- * -EIO if data cannot be written into the buffer for any other reason.
- */
-static
-int lib_ring_buffer_try_reserve_slow(struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- struct lttng_ust_lib_ring_buffer_ctx *ctx,
- void *client_ctx)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- struct lttng_ust_shm_handle *handle = ctx->handle;
- unsigned long reserve_commit_diff, offset_cmp;
- int timeout_left_ms = lttng_ust_ringbuffer_get_timeout(chan);
-
-retry:
- offsets->begin = offset_cmp = v_read(config, &buf->offset);
- offsets->old = offsets->begin;
- offsets->switch_new_start = 0;
- offsets->switch_new_end = 0;
- offsets->switch_old_end = 0;
- offsets->pre_header_padding = 0;
-
- ctx->tsc = config->cb.ring_buffer_clock_read(chan);
- if ((int64_t) ctx->tsc == -EIO)
- return -EIO;
-
- if (last_tsc_overflow(config, buf, ctx->tsc))
- ctx->rflags |= RING_BUFFER_RFLAG_FULL_TSC;
-
- if (caa_unlikely(subbuf_offset(offsets->begin, ctx->chan) == 0)) {
- offsets->switch_new_start = 1; /* For offsets->begin */
- } else {
- offsets->size = config->cb.record_header_size(config, chan,
- offsets->begin,
- &offsets->pre_header_padding,
- ctx, client_ctx);
- offsets->size +=
- lib_ring_buffer_align(offsets->begin + offsets->size,
- ctx->largest_align)
- + ctx->data_size;
- if (caa_unlikely(subbuf_offset(offsets->begin, chan) +
- offsets->size > chan->backend.subbuf_size)) {
- offsets->switch_old_end = 1; /* For offsets->old */
- offsets->switch_new_start = 1; /* For offsets->begin */
- }
- }
- if (caa_unlikely(offsets->switch_new_start)) {
- unsigned long sb_index, commit_count;
- struct commit_counters_cold *cc_cold;
-
- /*
- * We are typically not filling the previous buffer completely.
- */
- if (caa_likely(offsets->switch_old_end))
- offsets->begin = subbuf_align(offsets->begin, chan);
- offsets->begin = offsets->begin
- + config->cb.subbuffer_header_size();
- /* Test new buffer integrity */
- sb_index = subbuf_index(offsets->begin, chan);
- /*
- * Read buf->offset before buf->commit_cold[sb_index].cc_sb.
- * lib_ring_buffer_check_deliver() has the matching
- * memory barriers required around commit_cold cc_sb
- * updates to ensure reserve and commit counter updates
- * are not seen reordered when updated by another CPU.
- */
- cmm_smp_rmb();
- cc_cold = shmp_index(handle, buf->commit_cold, sb_index);
- if (!cc_cold)
- return -1;
- commit_count = v_read(config, &cc_cold->cc_sb);
- /* Read buf->commit_cold[sb_index].cc_sb before buf->offset. */
- cmm_smp_rmb();
- if (caa_unlikely(offset_cmp != v_read(config, &buf->offset))) {
- /*
- * The reserve counter have been concurrently updated
- * while we read the commit counter. This means the
- * commit counter we read might not match buf->offset
- * due to concurrent update. We therefore need to retry.
- */
- goto retry;
- }
- reserve_commit_diff =
- (buf_trunc(offsets->begin, chan)
- >> chan->backend.num_subbuf_order)
- - (commit_count & chan->commit_count_mask);
- if (caa_likely(reserve_commit_diff == 0)) {
- /* Next subbuffer not being written to. */
- if (caa_unlikely(config->mode != RING_BUFFER_OVERWRITE &&
- subbuf_trunc(offsets->begin, chan)
- - subbuf_trunc((unsigned long)
- uatomic_read(&buf->consumed), chan)
- >= chan->backend.buf_size)) {
- unsigned long nr_lost;
-
- if (handle_blocking_retry(&timeout_left_ms))
- goto retry;
-
- /*
- * We do not overwrite non consumed buffers
- * and we are full : record is lost.
- */
- nr_lost = v_read(config, &buf->records_lost_full);
- v_inc(config, &buf->records_lost_full);
- if ((nr_lost & (DBG_PRINT_NR_LOST - 1)) == 0) {
- DBG("%lu or more records lost in (%s:%d) (buffer full)\n",
- nr_lost + 1, chan->backend.name,
- buf->backend.cpu);
- }
- return -ENOBUFS;
- } else {
- /*
- * Next subbuffer not being written to, and we
- * are either in overwrite mode or the buffer is
- * not full. It's safe to write in this new
- * subbuffer.
- */
- }
- } else {
- unsigned long nr_lost;
-
- /*
- * Next subbuffer reserve offset does not match the
- * commit offset, and this did not involve update to the
- * reserve counter. Drop record in producer-consumer and
- * overwrite mode. Caused by either a writer OOPS or too
- * many nested writes over a reserve/commit pair.
- */
- nr_lost = v_read(config, &buf->records_lost_wrap);
- v_inc(config, &buf->records_lost_wrap);
- if ((nr_lost & (DBG_PRINT_NR_LOST - 1)) == 0) {
- DBG("%lu or more records lost in (%s:%d) (wrap-around)\n",
- nr_lost + 1, chan->backend.name,
- buf->backend.cpu);
- }
- return -EIO;
- }
- offsets->size =
- config->cb.record_header_size(config, chan,
- offsets->begin,
- &offsets->pre_header_padding,
- ctx, client_ctx);
- offsets->size +=
- lib_ring_buffer_align(offsets->begin + offsets->size,
- ctx->largest_align)
- + ctx->data_size;
- if (caa_unlikely(subbuf_offset(offsets->begin, chan)
- + offsets->size > chan->backend.subbuf_size)) {
- unsigned long nr_lost;
-
- /*
- * Record too big for subbuffers, report error, don't
- * complete the sub-buffer switch.
- */
- nr_lost = v_read(config, &buf->records_lost_big);
- v_inc(config, &buf->records_lost_big);
- if ((nr_lost & (DBG_PRINT_NR_LOST - 1)) == 0) {
- DBG("%lu or more records lost in (%s:%d) record size "
- " of %zu bytes is too large for buffer\n",
- nr_lost + 1, chan->backend.name,
- buf->backend.cpu, offsets->size);
- }
- return -ENOSPC;
- } else {
- /*
- * We just made a successful buffer switch and the
- * record fits in the new subbuffer. Let's write.
- */
- }
- } else {
- /*
- * Record fits in the current buffer and we are not on a switch
- * boundary. It's safe to write.
- */
- }
- offsets->end = offsets->begin + offsets->size;
-
- if (caa_unlikely(subbuf_offset(offsets->end, chan) == 0)) {
- /*
- * The offset_end will fall at the very beginning of the next
- * subbuffer.
- */
- offsets->switch_new_end = 1; /* For offsets->begin */
- }
- return 0;
-}
-
-/**
- * lib_ring_buffer_reserve_slow - Atomic slot reservation in a buffer.
- * @ctx: ring buffer context.
- *
- * Return : -NOBUFS if not enough space, -ENOSPC if event size too large,
- * -EIO for other errors, else returns 0.
- * It will take care of sub-buffer switching.
- */
-int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx,
- void *client_ctx)
-{
- struct channel *chan = ctx->chan;
- struct lttng_ust_shm_handle *handle = ctx->handle;
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- struct lttng_ust_lib_ring_buffer *buf;
- struct switch_offsets offsets;
- int ret;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- buf = shmp(handle, chan->backend.buf[ctx->cpu].shmp);
- else
- buf = shmp(handle, chan->backend.buf[0].shmp);
- if (!buf)
- return -EIO;
- ctx->buf = buf;
-
- offsets.size = 0;
-
- do {
- ret = lib_ring_buffer_try_reserve_slow(buf, chan, &offsets,
- ctx, client_ctx);
- if (caa_unlikely(ret))
- return ret;
- } while (caa_unlikely(v_cmpxchg(config, &buf->offset, offsets.old,
- offsets.end)
- != offsets.old));
-
- /*
- * Atomically update last_tsc. This update races against concurrent
- * atomic updates, but the race will always cause supplementary full TSC
- * records, never the opposite (missing a full TSC record when it would
- * be needed).
- */
- save_last_tsc(config, buf, ctx->tsc);
-
- /*
- * Push the reader if necessary
- */
- lib_ring_buffer_reserve_push_reader(buf, chan, offsets.end - 1);
-
- /*
- * Clear noref flag for this subbuffer.
- */
- lib_ring_buffer_clear_noref(config, &buf->backend,
- subbuf_index(offsets.end - 1, chan),
- handle);
-
- /*
- * Switch old subbuffer if needed.
- */
- if (caa_unlikely(offsets.switch_old_end)) {
- lib_ring_buffer_clear_noref(config, &buf->backend,
- subbuf_index(offsets.old - 1, chan),
- handle);
- lib_ring_buffer_switch_old_end(buf, chan, &offsets, ctx->tsc, handle);
- }
-
- /*
- * Populate new subbuffer.
- */
- if (caa_unlikely(offsets.switch_new_start))
- lib_ring_buffer_switch_new_start(buf, chan, &offsets, ctx->tsc, handle);
-
- if (caa_unlikely(offsets.switch_new_end))
- lib_ring_buffer_switch_new_end(buf, chan, &offsets, ctx->tsc, handle);
-
- ctx->slot_size = offsets.size;
- ctx->pre_offset = offsets.begin;
- ctx->buf_offset = offsets.begin + offsets.pre_header_padding;
- return 0;
-}
-
-static
-void lib_ring_buffer_vmcore_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf,
- unsigned long commit_count,
- unsigned long idx,
- struct lttng_ust_shm_handle *handle)
-{
- struct commit_counters_hot *cc_hot;
-
- if (config->oops != RING_BUFFER_OOPS_CONSISTENCY)
- return;
- cc_hot = shmp_index(handle, buf->commit_hot, idx);
- if (!cc_hot)
- return;
- v_set(config, &cc_hot->seq, commit_count);
-}
-
-/*
- * The ring buffer can count events recorded and overwritten per buffer,
- * but it is disabled by default due to its performance overhead.
- */
-#ifdef LTTNG_RING_BUFFER_COUNT_EVENTS
-static
-void deliver_count_events(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf,
- unsigned long idx,
- struct lttng_ust_shm_handle *handle)
-{
- v_add(config, subbuffer_get_records_count(config,
- &buf->backend, idx, handle),
- &buf->records_count);
- v_add(config, subbuffer_count_records_overrun(config,
- &buf->backend, idx, handle),
- &buf->records_overrun);
-}
-#else /* LTTNG_RING_BUFFER_COUNT_EVENTS */
-static
-void deliver_count_events(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf,
- unsigned long idx,
- struct lttng_ust_shm_handle *handle)
-{
-}
-#endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */
-
-void lib_ring_buffer_check_deliver_slow(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- unsigned long offset,
- unsigned long commit_count,
- unsigned long idx,
- struct lttng_ust_shm_handle *handle,
- uint64_t tsc)
-{
- unsigned long old_commit_count = commit_count
- - chan->backend.subbuf_size;
- struct commit_counters_cold *cc_cold;
-
- /*
- * If we succeeded at updating cc_sb below, we are the subbuffer
- * writer delivering the subbuffer. Deals with concurrent
- * updates of the "cc" value without adding a add_return atomic
- * operation to the fast path.
- *
- * We are doing the delivery in two steps:
- * - First, we cmpxchg() cc_sb to the new value
- * old_commit_count + 1. This ensures that we are the only
- * subbuffer user successfully filling the subbuffer, but we
- * do _not_ set the cc_sb value to "commit_count" yet.
- * Therefore, other writers that would wrap around the ring
- * buffer and try to start writing to our subbuffer would
- * have to drop records, because it would appear as
- * non-filled.
- * We therefore have exclusive access to the subbuffer control
- * structures. This mutual exclusion with other writers is
- * crucially important to perform record overruns count in
- * flight recorder mode locklessly.
- * - When we are ready to release the subbuffer (either for
- * reading or for overrun by other writers), we simply set the
- * cc_sb value to "commit_count" and perform delivery.
- *
- * The subbuffer size is least 2 bytes (minimum size: 1 page).
- * This guarantees that old_commit_count + 1 != commit_count.
- */
-
- /*
- * Order prior updates to reserve count prior to the
- * commit_cold cc_sb update.
- */
- cmm_smp_wmb();
- cc_cold = shmp_index(handle, buf->commit_cold, idx);
- if (!cc_cold)
- return;
- if (caa_likely(v_cmpxchg(config, &cc_cold->cc_sb,
- old_commit_count, old_commit_count + 1)
- == old_commit_count)) {
- uint64_t *ts_end;
-
- /*
- * Start of exclusive subbuffer access. We are
- * guaranteed to be the last writer in this subbuffer
- * and any other writer trying to access this subbuffer
- * in this state is required to drop records.
- *
- * We can read the ts_end for the current sub-buffer
- * which has been saved by the very last space
- * reservation for the current sub-buffer.
- *
- * Order increment of commit counter before reading ts_end.
- */
- cmm_smp_mb();
- ts_end = shmp_index(handle, buf->ts_end, idx);
- if (!ts_end)
- return;
- deliver_count_events(config, buf, idx, handle);
- config->cb.buffer_end(buf, *ts_end, idx,
- lib_ring_buffer_get_data_size(config,
- buf,
- idx,
- handle),
- handle);
-
- /*
- * Increment the packet counter while we have exclusive
- * access.
- */
- subbuffer_inc_packet_count(config, &buf->backend, idx, handle);
-
- /*
- * Set noref flag and offset for this subbuffer id.
- * Contains a memory barrier that ensures counter stores
- * are ordered before set noref and offset.
- */
- lib_ring_buffer_set_noref_offset(config, &buf->backend, idx,
- buf_trunc_val(offset, chan), handle);
-
- /*
- * Order set_noref and record counter updates before the
- * end of subbuffer exclusive access. Orders with
- * respect to writers coming into the subbuffer after
- * wrap around, and also order wrt concurrent readers.
- */
- cmm_smp_mb();
- /* End of exclusive subbuffer access */
- v_set(config, &cc_cold->cc_sb, commit_count);
- /*
- * Order later updates to reserve count after
- * the commit cold cc_sb update.
- */
- cmm_smp_wmb();
- lib_ring_buffer_vmcore_check_deliver(config, buf,
- commit_count, idx, handle);
-
- /*
- * RING_BUFFER_WAKEUP_BY_WRITER wakeup is not lock-free.
- */
- if (config->wakeup == RING_BUFFER_WAKEUP_BY_WRITER
- && uatomic_read(&buf->active_readers)
- && lib_ring_buffer_poll_deliver(config, buf, chan, handle)) {
- lib_ring_buffer_wakeup(buf, handle);
- }
- }
-}
-
-/*
- * Force a read (imply TLS fixup for dlopen) of TLS variables.
- */
-void lttng_fixup_ringbuffer_tls(void)
-{
- asm volatile ("" : : "m" (URCU_TLS(lib_ring_buffer_nesting)));
-}
-
-void lib_ringbuffer_signal_init(void)
-{
- sigset_t mask;
- int ret;
-
- /*
- * Block signal for entire process, so only our thread processes
- * it.
- */
- rb_setmask(&mask);
- ret = pthread_sigmask(SIG_BLOCK, &mask, NULL);
- if (ret) {
- errno = ret;
- PERROR("pthread_sigmask");
- }
-}
projects / lttng-ust.git / blobdiff