+++ /dev/null
-/*
- * ring_buffer_frontend.c
- *
- * (C) Copyright 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * 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
- *
- * Dual LGPL v2.1/GPL v2 license.
- */
-
-#define _GNU_SOURCE
-#include <sys/types.h>
-#include <sys/mman.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <urcu/compiler.h>
-#include <urcu/ref.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 "tlsfixup.h"
-#include "../liblttng-ust/compat.h" /* For ENODATA */
-
-#ifndef max
-#define max(a, b) ((a) > (b) ? (a) : (b))
-#endif
-
-/* Print DBG() messages about events lost only every 1048576 hits */
-#define DBG_PRINT_NR_LOST (1UL << 20)
-
-/*
- * 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;
-};
-
-__thread unsigned int lib_ring_buffer_nesting;
-
-/*
- * TODO: this is unused. Errors are saved within the ring buffer.
- * Eventually, allow consumerd to print these errors.
- */
-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)
- __attribute__((unused));
-
-/**
- * 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 = shmp(handle, buf->backend.chan);
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned int i;
-
- /*
- * 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++) {
- v_set(config, &shmp_index(handle, buf->commit_hot, i)->cc, 0);
- v_set(config, &shmp_index(handle, buf->commit_hot, i)->seq, 0);
- v_set(config, &shmp_index(handle, buf->commit_cold, i)->cc_sb, 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 */
-}
-
-/*
- * 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);
- 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;
-
- ret = lib_ring_buffer_backend_create(&buf->backend, &chan->backend,
- cpu, handle, shmobj);
- if (ret)
- return ret;
-
- 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)) {
- ret = -ENOMEM;
- goto free_chanbuf;
- }
-
- 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;
- }
-
- /*
- * 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);
- subbuffer_id_clear_noref(config, &shmp_index(handle, buf->backend.buf_wsb, 0)->id);
- tsc = config->cb.ring_buffer_clock_read(shmp(handle, buf->backend.chan));
- config->cb.buffer_begin(buf, tsc, 0, handle);
- v_add(config, subbuf_header_size, &shmp_index(handle, buf->commit_hot, 0)->cc);
-
- if (config->cb.buffer_create) {
- ret = config->cb.buffer_create(buf, priv, cpu, chanb->name, handle);
- if (ret)
- goto free_init;
- }
- buf->backend.allocated = 1;
- return 0;
-
- /* Error handling */
-free_init:
- /* commit_cold will be freed by shm teardown */
-free_commit:
- /* commit_hot will be freed by shm teardown */
-free_chanbuf:
- return ret;
-}
-
-#if 0
-static void switch_buffer_timer(unsigned long data)
-{
- struct lttng_ust_lib_ring_buffer *buf = (struct lttng_ust_lib_ring_buffer *)data;
- struct channel *chan = shmp(handle, buf->backend.chan);
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
-
- /*
- * Only flush buffers periodically if readers are active.
- */
- if (uatomic_read(&buf->active_readers) || uatomic_read(&buf->active_shadow_readers))
- lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE, handle);
-
- //TODO timers
- //if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- // mod_timer_pinned(&buf->switch_timer,
- // jiffies + chan->switch_timer_interval);
- //else
- // mod_timer(&buf->switch_timer,
- // jiffies + chan->switch_timer_interval);
-}
-#endif //0
-
-static void lib_ring_buffer_start_switch_timer(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle)
-{
- struct channel *chan = shmp(handle, buf->backend.chan);
- //const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
-
- if (!chan->switch_timer_interval || buf->switch_timer_enabled)
- return;
- //TODO
- //init_timer(&buf->switch_timer);
- //buf->switch_timer.function = switch_buffer_timer;
- //buf->switch_timer.expires = jiffies + chan->switch_timer_interval;
- //buf->switch_timer.data = (unsigned long)buf;
- //if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- // add_timer_on(&buf->switch_timer, buf->backend.cpu);
- //else
- // add_timer(&buf->switch_timer);
- buf->switch_timer_enabled = 1;
-}
-
-static void lib_ring_buffer_stop_switch_timer(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle)
-{
- struct channel *chan = shmp(handle, buf->backend.chan);
-
- if (!chan->switch_timer_interval || !buf->switch_timer_enabled)
- return;
-
- //TODO
- //del_timer_sync(&buf->switch_timer);
- buf->switch_timer_enabled = 0;
-}
-
-#if 0
-/*
- * Polling timer to check the channels for data.
- */
-static void read_buffer_timer(unsigned long data)
-{
- struct lttng_ust_lib_ring_buffer *buf = (struct lttng_ust_lib_ring_buffer *)data;
- struct channel *chan = shmp(handle, buf->backend.chan);
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
-
- CHAN_WARN_ON(chan, !buf->backend.allocated);
-
- if (uatomic_read(&buf->active_readers) || uatomic_read(&buf->active_shadow_readers))
- && lib_ring_buffer_poll_deliver(config, buf, chan)) {
- //TODO
- //wake_up_interruptible(&buf->read_wait);
- //wake_up_interruptible(&chan->read_wait);
- }
-
- //TODO
- //if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- // mod_timer_pinned(&buf->read_timer,
- // jiffies + chan->read_timer_interval);
- //else
- // mod_timer(&buf->read_timer,
- // jiffies + chan->read_timer_interval);
-}
-#endif //0
-
-static void lib_ring_buffer_start_read_timer(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle)
-{
- struct channel *chan = shmp(handle, buf->backend.chan);
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
-
- if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER
- || !chan->read_timer_interval
- || buf->read_timer_enabled)
- return;
-
- //TODO
- //init_timer(&buf->read_timer);
- //buf->read_timer.function = read_buffer_timer;
- //buf->read_timer.expires = jiffies + chan->read_timer_interval;
- //buf->read_timer.data = (unsigned long)buf;
-
- //if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- // add_timer_on(&buf->read_timer, buf->backend.cpu);
- //else
- // add_timer(&buf->read_timer);
- buf->read_timer_enabled = 1;
-}
-
-static void lib_ring_buffer_stop_read_timer(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle)
-{
- struct channel *chan = shmp(handle, buf->backend.chan);
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
-
- if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER
- || !chan->read_timer_interval
- || !buf->read_timer_enabled)
- return;
-
- //TODO
- //del_timer_sync(&buf->read_timer);
- /*
- * do one more check to catch data that has been written in the last
- * timer period.
- */
- if (lib_ring_buffer_poll_deliver(config, buf, chan, handle)) {
- //TODO
- //wake_up_interruptible(&buf->read_wait);
- //wake_up_interruptible(&chan->read_wait);
- }
- buf->read_timer_enabled = 0;
-}
-
-static void channel_unregister_notifiers(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);
-
- lib_ring_buffer_stop_switch_timer(buf, handle);
- lib_ring_buffer_stop_read_timer(buf, handle);
- }
- } else {
- struct lttng_ust_lib_ring_buffer *buf = shmp(handle, chan->backend.buf[0].shmp);
-
- lib_ring_buffer_stop_switch_timer(buf, handle);
- lib_ring_buffer_stop_read_timer(buf, handle);
- }
- //channel_backend_unregister_notifiers(&chan->backend);
-}
-
-static void channel_free(struct channel *chan, struct lttng_ust_shm_handle *handle,
- int shadow)
-{
- if (!shadow)
- channel_backend_free(&chan->backend, handle);
- /* chan is freed by shm teardown */
- shm_object_table_destroy(handle->table);
- 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.
- *
- * 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,
- int **shm_fd, int **wait_fd, uint64_t **memory_map_size)
-{
- int ret, cpu;
- size_t shmsize, chansize;
- struct channel *chan;
- struct lttng_ust_shm_handle *handle;
- struct shm_object *shmobj;
- struct shm_ref *ref;
-
- 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));
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- shmsize += sizeof(struct lttng_ust_lib_ring_buffer_shmp) * num_possible_cpus();
- else
- shmsize += sizeof(struct lttng_ust_lib_ring_buffer_shmp);
- chansize = shmsize;
- shmsize += offset_align(shmsize, priv_data_align);
- shmsize += priv_data_size;
-
- shmobj = shm_object_table_append(handle->table, shmsize);
- 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;
-
- /* 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;
- *priv_data = NULL;
- }
-
- ret = channel_backend_init(&chan->backend, name, config,
- subbuf_size, num_subbuf, handle);
- if (ret)
- goto error_backend_init;
-
- chan->commit_count_mask = (~0UL >> chan->backend.num_subbuf_order);
- //TODO
- //chan->switch_timer_interval = usecs_to_jiffies(switch_timer_interval);
- //chan->read_timer_interval = usecs_to_jiffies(read_timer_interval);
- //TODO
- //init_waitqueue_head(&chan->read_wait);
- //init_waitqueue_head(&chan->hp_wait);
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
- /*
- * In case of non-hotplug cpu, if the ring-buffer is allocated
- * in early initcall, it will not be notified of secondary cpus.
- * In that off case, we need to allocate for all possible cpus.
- */
- for_each_possible_cpu(cpu) {
- struct lttng_ust_lib_ring_buffer *buf = shmp(handle, chan->backend.buf[cpu].shmp);
- lib_ring_buffer_start_switch_timer(buf, handle);
- lib_ring_buffer_start_read_timer(buf, handle);
- }
- } else {
- struct lttng_ust_lib_ring_buffer *buf = shmp(handle, chan->backend.buf[0].shmp);
-
- lib_ring_buffer_start_switch_timer(buf, handle);
- lib_ring_buffer_start_read_timer(buf, handle);
- }
- ref = &handle->chan._ref;
- shm_get_object_data(handle, ref, shm_fd, wait_fd, memory_map_size);
- return handle;
-
-error_backend_init:
-error_append:
- shm_object_table_destroy(handle->table);
-error_table_alloc:
- free(handle);
- return NULL;
-}
-
-struct lttng_ust_shm_handle *channel_handle_create(int shm_fd, int wait_fd,
- uint64_t memory_map_size)
-{
- 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_shadow(handle->table,
- shm_fd, wait_fd, memory_map_size);
- 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);
-error_table_alloc:
- free(handle);
- return NULL;
-}
-
-int channel_handle_add_stream(struct lttng_ust_shm_handle *handle,
- int shm_fd, int wait_fd, uint64_t memory_map_size)
-{
- struct shm_object *object;
-
- /* Add stream object */
- object = shm_object_table_append_shadow(handle->table,
- shm_fd, wait_fd, memory_map_size);
- if (!object)
- return -1;
- return 0;
-}
-
-static
-void channel_release(struct channel *chan, struct lttng_ust_shm_handle *handle,
- int shadow)
-{
- channel_free(chan, handle, shadow);
-}
-
-/**
- * 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 shadow)
-{
- if (shadow) {
- channel_release(chan, handle, shadow);
- return;
- }
-
- channel_unregister_notifiers(chan, handle);
-
- /*
- * Note: the consumer takes care of finalizing and switching the
- * buffers.
- */
-
- /*
- * sessiond/consumer are keeping a reference on the shm file
- * descriptor directly. No need to refcount.
- */
- channel_release(chan, handle, shadow);
- 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,
- uint64_t **memory_map_size)
-{
- struct shm_ref *ref;
-
- if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
- ref = &chan->backend.buf[0].shmp._ref;
- shm_get_object_data(handle, ref, shm_fd, wait_fd,
- memory_map_size);
- return shmp(handle, chan->backend.buf[0].shmp);
- } else {
- if (cpu >= num_possible_cpus())
- return NULL;
- ref = &chan->backend.buf[cpu].shmp._ref;
- shm_get_object_data(handle, ref, shm_fd, wait_fd,
- memory_map_size);
- return shmp(handle, chan->backend.buf[cpu].shmp);
- }
-}
-
-int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle,
- int shadow)
-{
- if (shadow) {
- if (uatomic_cmpxchg(&buf->active_shadow_readers, 0, 1) != 0)
- return -EBUSY;
- cmm_smp_mb();
- return 0;
- }
- 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,
- int shadow)
-{
- struct channel *chan = shmp(handle, buf->backend.chan);
-
- if (shadow) {
- CHAN_WARN_ON(chan, uatomic_read(&buf->active_shadow_readers) != 1);
- cmm_smp_mb();
- uatomic_dec(&buf->active_shadow_readers);
- 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 = shmp(handle, buf->backend.chan);
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long consumed_cur, write_offset;
- int finalized;
-
- 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;
-}
-
-/**
- * lib_ring_buffer_put_snapshot - 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 = shmp(handle, bufb->chan);
- unsigned long consumed;
-
- CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1
- && uatomic_read(&buf->active_shadow_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 = shmp(handle, buf->backend.chan);
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long consumed_cur, consumed_idx, commit_count, write_offset;
- int ret;
- int finalized;
-
-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);
- commit_count = v_read(config, &shmp_index(handle, buf->commit_cold, consumed_idx)->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.
- */
- if (((commit_count - chan->backend.subbuf_size)
- & chan->commit_count_mask)
- - (buf_trunc(consumed_cur, chan)
- >> chan->backend.num_subbuf_order)
- != 0)
- 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_cur, 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.
- */
- ret = update_read_sb_index(config, &buf->backend, &chan->backend,
- consumed_idx, buf_trunc_val(consumed, chan),
- handle);
- if (ret)
- goto retry;
- 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 = shmp(handle, bufb->chan);
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long read_sb_bindex, consumed_idx, consumed;
-
- CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1
- && uatomic_read(&buf->active_shadow_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.
- */
- read_sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
- v_add(config, v_read(config,
- &shmp(handle, shmp_index(handle, bufb->array, read_sb_bindex)->shmp)->records_unread),
- &bufb->records_read);
- v_set(config, &shmp(handle, shmp_index(handle, bufb->array, read_sb_bindex)->shmp)->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;
-
- cons_idx = subbuf_index(cons_offset, chan);
- commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, cons_idx)->cc);
- commit_count_sb = v_read(config, &shmp_index(handle, buf->commit_cold, cons_idx)->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);
-
- 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 when the buffer is finalized, in SWITCH_FLUSH.
- */
-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;
-
- 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();
- v_add(config, config->cb.subbuffer_header_size(),
- &shmp_index(handle, buf->commit_hot, oldidx)->cc);
- commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, oldidx)->cc);
- /* Check if the written buffer has to be delivered */
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->old,
- commit_count, oldidx, handle);
- lib_ring_buffer_write_commit_counter(config, buf, chan, oldidx,
- offsets->old, commit_count,
- config->cb.subbuffer_header_size(),
- handle);
-}
-
-/*
- * 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;
-
- 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);
-
- /*
- * Order all writes to buffer before the commit count update that will
- * determine that the subbuffer is full.
- */
- cmm_smp_wmb();
- v_add(config, padding_size, &shmp_index(handle, buf->commit_hot, oldidx)->cc);
- commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, oldidx)->cc);
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->old - 1,
- commit_count, oldidx, handle);
- lib_ring_buffer_write_commit_counter(config, buf, chan, oldidx,
- offsets->old, commit_count,
- padding_size, handle);
-}
-
-/*
- * 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;
-
- 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();
- v_add(config, config->cb.subbuffer_header_size(),
- &shmp_index(handle, buf->commit_hot, beginidx)->cc);
- commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, beginidx)->cc);
- /* Check if the written buffer has to be delivered */
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->begin,
- commit_count, beginidx, handle);
- lib_ring_buffer_write_commit_counter(config, buf, chan, beginidx,
- offsets->begin, commit_count,
- config->cb.subbuffer_header_size(),
- handle);
-}
-
-/*
- * lib_ring_buffer_switch_new_end: finish switching current subbuffer
- *
- * The only remaining threads could be the ones with pending commits. They will
- * have to do the deliver themselves.
- */
-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 = subbuf_index(offsets->end - 1, chan);
- unsigned long commit_count, padding_size, data_size;
-
- data_size = subbuf_offset(offsets->end - 1, chan) + 1;
- padding_size = chan->backend.subbuf_size - data_size;
- subbuffer_set_data_size(config, &buf->backend, endidx, data_size,
- handle);
-
- /*
- * Order all writes to buffer before the commit count update that will
- * determine that the subbuffer is full.
- */
- cmm_smp_wmb();
- v_add(config, padding_size, &shmp_index(handle, buf->commit_hot, endidx)->cc);
- commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, endidx)->cc);
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->end - 1,
- commit_count, endidx, handle);
- lib_ring_buffer_write_commit_counter(config, buf, chan, endidx,
- offsets->end, commit_count,
- padding_size, handle);
-}
-
-/*
- * 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)
-{
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long off;
-
- 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 > 0) {
- if (caa_unlikely(off == 0)) {
- /*
- * The client does not save any header information.
- * 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;
- /*
- * Need to write the subbuffer start header on finalize.
- */
- offsets->switch_old_start = 1;
- }
- offsets->begin = subbuf_align(offsets->begin, chan);
- } else
- return -1; /* we do not have to switch : buffer is empty */
- /* 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.
- *
- * Note, however, that 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.
- */
-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 = shmp(handle, buf->backend.chan);
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
- struct switch_offsets offsets;
- unsigned long oldidx;
- uint64_t tsc;
-
- offsets.size = 0;
-
- /*
- * Perform retryable operations.
- */
- do {
- if (lib_ring_buffer_try_switch_slow(mode, buf, chan, &offsets,
- &tsc))
- 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);
-}
-
-/*
- * 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)
-{
- 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;
-
- offsets->begin = 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);
- 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;
-
- /*
- * 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);
- reserve_commit_diff =
- (buf_trunc(offsets->begin, chan)
- >> chan->backend.num_subbuf_order)
- - ((unsigned long) v_read(config,
- &shmp_index(handle, buf->commit_cold, sb_index)->cc_sb)
- & 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;
-
- /*
- * 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. 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);
- 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)
-{
- 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);
- ctx->buf = buf;
-
- offsets.size = 0;
-
- do {
- ret = lib_ring_buffer_try_reserve_slow(buf, chan, &offsets,
- 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;
-}
-
-/*
- * Force a read (imply TLS fixup for dlopen) of TLS variables.
- */
-void lttng_fixup_ringbuffer_tls(void)
-{
- asm volatile ("" : : "m" (lib_ring_buffer_nesting));
-}
projects / lttng-ust.git / blobdiff