X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=libringbuffer%2Ffrontend_internal.h;h=1a9c2d4b78e82e7645e1267430b41e6f0c3218c2;hb=HEAD;hp=a96746dcc53533910e76baaa15ab28e0133fd566;hpb=8c90a710949a214d87084ff67fc85f284bc93ef2;p=lttng-ust.git diff --git a/libringbuffer/frontend_internal.h b/libringbuffer/frontend_internal.h deleted file mode 100644 index a96746dc..00000000 --- a/libringbuffer/frontend_internal.h +++ /dev/null @@ -1,526 +0,0 @@ -#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 - * - * 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 - * - * See ring_buffer_frontend.c for more information on wait-free algorithms. - * - * Dual LGPL v2.1/GPL v2 license. - */ - -#include -#include -#include -#include - -#include -#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_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) -{ - unsigned long old_commit_count = commit_count - - chan->backend.subbuf_size; - uint64_t tsc; - - /* 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. - */ - 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. - */ - tsc = config->cb.ring_buffer_clock_read(chan); - 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); - - /* - * 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); - 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)) { - int wakeup_fd = shm_get_wakeup_fd(handle, &buf->self._ref); - - if (wakeup_fd >= 0) { - sigset_t sigpipe_set, pending_set, old_set; - int ret, sigpipe_was_pending = 0; - - /* - * 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); - } - } - } - } - } -} - -/* - * 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, - size_t slot_size, - struct lttng_ust_shm_handle *handle) -{ - unsigned long offset, commit_seq_old; - - if (config->oops != RING_BUFFER_OOPS_CONSISTENCY) - return; - - offset = buf_offset + slot_size; - - /* - * 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(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 */