+++ /dev/null
-#ifndef _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H
-#define _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H
-
-/*
- * libringbuffer/frontend_internal.h
- *
- * Ring Buffer Library Synchronization Header (internal helpers).
- *
- * 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
- *
- *
- * Author:
- * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * See ring_buffer_frontend.c for more information on wait-free algorithms.
- *
- * Dual LGPL v2.1/GPL v2 license.
- */
-
-#include <urcu/compiler.h>
-#include <urcu/tls-compat.h>
-#include <signal.h>
-#include <pthread.h>
-
-#include <lttng/ringbuffer-config.h>
-#include "backend_types.h"
-#include "frontend_types.h"
-#include "shm.h"
-
-/* Buffer offset macros */
-
-/* buf_trunc mask selects only the buffer number. */
-static inline
-unsigned long buf_trunc(unsigned long offset, struct channel *chan)
-{
- return offset & ~(chan->backend.buf_size - 1);
-
-}
-
-/* Select the buffer number value (counter). */
-static inline
-unsigned long buf_trunc_val(unsigned long offset, struct channel *chan)
-{
- return buf_trunc(offset, chan) >> chan->backend.buf_size_order;
-}
-
-/* buf_offset mask selects only the offset within the current buffer. */
-static inline
-unsigned long buf_offset(unsigned long offset, struct channel *chan)
-{
- return offset & (chan->backend.buf_size - 1);
-}
-
-/* subbuf_offset mask selects the offset within the current subbuffer. */
-static inline
-unsigned long subbuf_offset(unsigned long offset, struct channel *chan)
-{
- return offset & (chan->backend.subbuf_size - 1);
-}
-
-/* subbuf_trunc mask selects the subbuffer number. */
-static inline
-unsigned long subbuf_trunc(unsigned long offset, struct channel *chan)
-{
- return offset & ~(chan->backend.subbuf_size - 1);
-}
-
-/* subbuf_align aligns the offset to the next subbuffer. */
-static inline
-unsigned long subbuf_align(unsigned long offset, struct channel *chan)
-{
- return (offset + chan->backend.subbuf_size)
- & ~(chan->backend.subbuf_size - 1);
-}
-
-/* subbuf_index returns the index of the current subbuffer within the buffer. */
-static inline
-unsigned long subbuf_index(unsigned long offset, struct channel *chan)
-{
- return buf_offset(offset, chan) >> chan->backend.subbuf_size_order;
-}
-
-/*
- * Last TSC comparison functions. Check if the current TSC overflows tsc_bits
- * bits from the last TSC read. When overflows are detected, the full 64-bit
- * timestamp counter should be written in the record header. Reads and writes
- * last_tsc atomically.
- */
-
-#if (CAA_BITS_PER_LONG == 32)
-static inline
-void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
-{
- if (config->tsc_bits == 0 || config->tsc_bits == 64)
- return;
-
- /*
- * Ensure the compiler performs this update in a single instruction.
- */
- v_set(config, &buf->last_tsc, (unsigned long)(tsc >> config->tsc_bits));
-}
-
-static inline
-int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
-{
- unsigned long tsc_shifted;
-
- if (config->tsc_bits == 0 || config->tsc_bits == 64)
- return 0;
-
- tsc_shifted = (unsigned long)(tsc >> config->tsc_bits);
- if (caa_unlikely(tsc_shifted
- - (unsigned long)v_read(config, &buf->last_tsc)))
- return 1;
- else
- return 0;
-}
-#else
-static inline
-void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
-{
- if (config->tsc_bits == 0 || config->tsc_bits == 64)
- return;
-
- v_set(config, &buf->last_tsc, (unsigned long)tsc);
-}
-
-static inline
-int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
-{
- if (config->tsc_bits == 0 || config->tsc_bits == 64)
- return 0;
-
- if (caa_unlikely((tsc - v_read(config, &buf->last_tsc))
- >> config->tsc_bits))
- return 1;
- else
- return 0;
-}
-#endif
-
-extern
-int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx);
-
-extern
-void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf,
- enum switch_mode mode,
- struct lttng_ust_shm_handle *handle);
-
-/* Buffer write helpers */
-
-static inline
-void lib_ring_buffer_reserve_push_reader(struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- unsigned long offset)
-{
- unsigned long consumed_old, consumed_new;
-
- do {
- consumed_old = uatomic_read(&buf->consumed);
- /*
- * If buffer is in overwrite mode, push the reader consumed
- * count if the write position has reached it and we are not
- * at the first iteration (don't push the reader farther than
- * the writer). This operation can be done concurrently by many
- * writers in the same buffer, the writer being at the farthest
- * write position sub-buffer index in the buffer being the one
- * which will win this loop.
- */
- if (caa_unlikely(subbuf_trunc(offset, chan)
- - subbuf_trunc(consumed_old, chan)
- >= chan->backend.buf_size))
- consumed_new = subbuf_align(consumed_old, chan);
- else
- return;
- } while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old,
- consumed_new) != consumed_old));
-}
-
-static inline
-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)
-{
- if (config->oops == RING_BUFFER_OOPS_CONSISTENCY)
- v_set(config, &shmp_index(handle, buf->commit_hot, idx)->seq, commit_count);
-}
-
-static inline
-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;
-
- consumed_old = uatomic_read(&buf->consumed);
- consumed_idx = subbuf_index(consumed_old, chan);
- commit_count = v_read(config, &shmp_index(handle, buf->commit_cold, consumed_idx)->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 inline
-int lib_ring_buffer_pending_data(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan)
-{
- return !!subbuf_offset(v_read(config, &buf->offset), chan);
-}
-
-static inline
-unsigned long lib_ring_buffer_get_data_size(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)
-{
- return subbuffer_get_data_size(config, &buf->backend, idx, handle);
-}
-
-/*
- * Check if all space reservation in a buffer have been committed. This helps
- * knowing if an execution context is nested (for per-cpu buffers only).
- * This is a very specific ftrace use-case, so we keep this as "internal" API.
- */
-static inline
-int lib_ring_buffer_reserve_committed(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 offset, idx, commit_count;
-
- CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU);
- CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU);
-
- /*
- * Read offset and commit count in a loop so they are both read
- * atomically wrt interrupts. By deal with interrupt concurrency by
- * restarting both reads if the offset has been pushed. Note that given
- * we only have to deal with interrupt concurrency here, an interrupt
- * modifying the commit count will also modify "offset", so it is safe
- * to only check for offset modifications.
- */
- do {
- offset = v_read(config, &buf->offset);
- idx = subbuf_index(offset, chan);
- commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, idx)->cc);
- } while (offset != v_read(config, &buf->offset));
-
- return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
- - (commit_count & chan->commit_count_mask) == 0);
-}
-
-static inline
-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);
- }
-}
-
-/*
- * Receive end of subbuffer TSC as parameter. It has been read in the
- * space reservation loop of either reserve or switch, which ensures it
- * progresses monotonically with event records in the buffer. Therefore,
- * it ensures that the end timestamp of a subbuffer is <= begin
- * timestamp of the following subbuffers.
- */
-static inline
-void lib_ring_buffer_check_deliver(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;
-
- /* Check if all commits have been done */
- if (caa_unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
- - (old_commit_count & chan->commit_count_mask) == 0)) {
- /*
- * 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();
- if (caa_likely(v_cmpxchg(config, &shmp_index(handle, buf->commit_cold, idx)->cc_sb,
- old_commit_count, old_commit_count + 1)
- == old_commit_count)) {
- /*
- * 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.
- */
- 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);
- config->cb.buffer_end(buf, tsc, 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, &shmp_index(handle, buf->commit_cold, idx)->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);
- }
- }
- }
-}
-
-/*
- * lib_ring_buffer_write_commit_counter
- *
- * For flight recording. must be called after commit.
- * This function increments the subbuffer's commit_seq counter each time the
- * commit count reaches back the reserve offset (modulo subbuffer size). It is
- * useful for crash dump.
- */
-static inline
-void lib_ring_buffer_write_commit_counter(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf,
- struct channel *chan,
- unsigned long idx,
- unsigned long buf_offset,
- unsigned long commit_count,
- struct lttng_ust_shm_handle *handle)
-{
- unsigned long commit_seq_old;
-
- if (config->oops != RING_BUFFER_OOPS_CONSISTENCY)
- return;
-
- /*
- * subbuf_offset includes commit_count_mask. We can simply
- * compare the offsets within the subbuffer without caring about
- * buffer full/empty mismatch because offset is never zero here
- * (subbuffer header and record headers have non-zero length).
- */
- if (caa_unlikely(subbuf_offset(buf_offset - commit_count, chan)))
- return;
-
- commit_seq_old = v_read(config, &shmp_index(handle, buf->commit_hot, idx)->seq);
- while ((long) (commit_seq_old - commit_count) < 0)
- commit_seq_old = v_cmpxchg(config, &shmp_index(handle, buf->commit_hot, idx)->seq,
- commit_seq_old, commit_count);
-}
-
-extern 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);
-extern void lib_ring_buffer_free(struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle);
-
-/* Keep track of trap nesting inside ring buffer code */
-extern DECLARE_URCU_TLS(unsigned int, lib_ring_buffer_nesting);
-
-#endif /* _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H */
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