+++ /dev/null
-/* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
- *
- * ring_buffer_frontend.c
- *
- * Copyright (C) 2005-2012 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
- */
-
-#include <linux/delay.h>
-#include <linux/module.h>
-#include <linux/percpu.h>
-#include <asm/cacheflush.h>
-
-#include <ringbuffer/config.h>
-#include <ringbuffer/backend.h>
-#include <ringbuffer/frontend.h>
-#include <ringbuffer/iterator.h>
-#include <ringbuffer/nohz.h>
-#include <wrapper/atomic.h>
-#include <wrapper/kref.h>
-#include <wrapper/percpu-defs.h>
-#include <wrapper/timer.h>
-#include <wrapper/vmalloc.h>
-
-/*
- * 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;
-};
-
-#ifdef CONFIG_NO_HZ
-enum tick_nohz_val {
- TICK_NOHZ_STOP,
- TICK_NOHZ_FLUSH,
- TICK_NOHZ_RESTART,
-};
-
-static ATOMIC_NOTIFIER_HEAD(tick_nohz_notifier);
-#endif /* CONFIG_NO_HZ */
-
-static DEFINE_PER_CPU(spinlock_t, ring_buffer_nohz_lock);
-
-DEFINE_PER_CPU(unsigned int, lib_ring_buffer_nesting);
-EXPORT_PER_CPU_SYMBOL(lib_ring_buffer_nesting);
-
-static
-void lib_ring_buffer_print_errors(struct channel *chan,
- struct lib_ring_buffer *buf, int cpu);
-static
-void _lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf,
- enum switch_mode mode);
-
-static
-int lib_ring_buffer_poll_deliver(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer *buf,
- struct channel *chan)
-{
- unsigned long consumed_old, consumed_idx, commit_count, write_offset;
-
- consumed_old = atomic_long_read(&buf->consumed);
- consumed_idx = subbuf_index(consumed_old, chan);
- commit_count = v_read(config, &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;
-}
-
-/*
- * Must be called under cpu hotplug protection.
- */
-void lib_ring_buffer_free(struct lib_ring_buffer *buf)
-{
- struct channel *chan = buf->backend.chan;
-
- lib_ring_buffer_print_errors(chan, buf, buf->backend.cpu);
- lttng_kvfree(buf->commit_hot);
- lttng_kvfree(buf->commit_cold);
- lttng_kvfree(buf->ts_end);
-
- lib_ring_buffer_backend_free(&buf->backend);
-}
-
-/**
- * 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 lib_ring_buffer *buf)
-{
- struct channel *chan = buf->backend.chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- unsigned int i;
-
- /*
- * Reset iterator first. It will put the subbuffer if it currently holds
- * it.
- */
- lib_ring_buffer_iterator_reset(buf);
- v_set(config, &buf->offset, 0);
- for (i = 0; i < chan->backend.num_subbuf; i++) {
- v_set(config, &buf->commit_hot[i].cc, 0);
- v_set(config, &buf->commit_hot[i].seq, 0);
- v_set(config, &buf->commit_cold[i].cc_sb, 0);
- buf->ts_end[i] = 0;
- }
- atomic_long_set(&buf->consumed, 0);
- atomic_set(&buf->record_disabled, 0);
- v_set(config, &buf->last_tsc, 0);
- lib_ring_buffer_backend_reset(&buf->backend);
- /* 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;
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_reset);
-
-/**
- * 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.
- */
- channel_iterator_reset(chan);
- atomic_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 */
-}
-EXPORT_SYMBOL_GPL(channel_reset);
-
-/*
- * Must be called under cpu hotplug protection.
- */
-int lib_ring_buffer_create(struct lib_ring_buffer *buf,
- struct channel_backend *chanb, int cpu)
-{
- const struct lib_ring_buffer_config *config = &chanb->config;
- struct channel *chan = container_of(chanb, struct channel, backend);
- void *priv = chanb->priv;
- size_t subbuf_header_size;
- u64 tsc;
- int ret;
-
- /* Test for cpu hotplug */
- if (buf->backend.allocated)
- return 0;
-
- /*
- * Paranoia: per cpu dynamic allocation is not officially documented as
- * zeroing the memory, so let's do it here too, just in case.
- */
- memset(buf, 0, sizeof(*buf));
-
- ret = lib_ring_buffer_backend_create(&buf->backend, &chan->backend, cpu);
- if (ret)
- return ret;
-
- buf->commit_hot =
- lttng_kvzalloc_node(ALIGN(sizeof(*buf->commit_hot)
- * chan->backend.num_subbuf,
- 1 << INTERNODE_CACHE_SHIFT),
- GFP_KERNEL | __GFP_NOWARN,
- cpu_to_node(max(cpu, 0)));
- if (!buf->commit_hot) {
- ret = -ENOMEM;
- goto free_chanbuf;
- }
-
- buf->commit_cold =
- lttng_kvzalloc_node(ALIGN(sizeof(*buf->commit_cold)
- * chan->backend.num_subbuf,
- 1 << INTERNODE_CACHE_SHIFT),
- GFP_KERNEL | __GFP_NOWARN,
- cpu_to_node(max(cpu, 0)));
- if (!buf->commit_cold) {
- ret = -ENOMEM;
- goto free_commit;
- }
-
- buf->ts_end =
- lttng_kvzalloc_node(ALIGN(sizeof(*buf->ts_end)
- * chan->backend.num_subbuf,
- 1 << INTERNODE_CACHE_SHIFT),
- GFP_KERNEL | __GFP_NOWARN,
- cpu_to_node(max(cpu, 0)));
- if (!buf->ts_end) {
- ret = -ENOMEM;
- goto free_commit_cold;
- }
-
- init_waitqueue_head(&buf->read_wait);
- init_waitqueue_head(&buf->write_wait);
- raw_spin_lock_init(&buf->raw_tick_nohz_spinlock);
-
- /*
- * 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, &buf->backend.buf_wsb[0].id);
- tsc = config->cb.ring_buffer_clock_read(buf->backend.chan);
- config->cb.buffer_begin(buf, tsc, 0);
- v_add(config, subbuf_header_size, &buf->commit_hot[0].cc);
-
- if (config->cb.buffer_create) {
- ret = config->cb.buffer_create(buf, priv, cpu, chanb->name);
- if (ret)
- goto free_init;
- }
-
- /*
- * Ensure the buffer is ready before setting it to allocated and setting
- * the cpumask.
- * Used for cpu hotplug vs cpumask iteration.
- */
- smp_wmb();
- buf->backend.allocated = 1;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
- CHAN_WARN_ON(chan, cpumask_test_cpu(cpu,
- chan->backend.cpumask));
- cpumask_set_cpu(cpu, chan->backend.cpumask);
- }
-
- return 0;
-
- /* Error handling */
-free_init:
- lttng_kvfree(buf->ts_end);
-free_commit_cold:
- lttng_kvfree(buf->commit_cold);
-free_commit:
- lttng_kvfree(buf->commit_hot);
-free_chanbuf:
- lib_ring_buffer_backend_free(&buf->backend);
- return ret;
-}
-
-static void switch_buffer_timer(LTTNG_TIMER_FUNC_ARG_TYPE t)
-{
- struct lib_ring_buffer *buf = lttng_from_timer(buf, t, switch_timer);
- struct channel *chan = buf->backend.chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- /*
- * Only flush buffers periodically if readers are active.
- */
- if (atomic_long_read(&buf->active_readers))
- lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE);
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- lttng_mod_timer_pinned(&buf->switch_timer,
- jiffies + chan->switch_timer_interval);
- else
- mod_timer(&buf->switch_timer,
- jiffies + chan->switch_timer_interval);
-}
-
-/*
- * Called with ring_buffer_nohz_lock held for per-cpu buffers.
- */
-static void lib_ring_buffer_start_switch_timer(struct lib_ring_buffer *buf)
-{
- struct channel *chan = buf->backend.chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- unsigned int flags = 0;
-
- if (!chan->switch_timer_interval || buf->switch_timer_enabled)
- return;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- flags = LTTNG_TIMER_PINNED;
-
- lttng_timer_setup(&buf->switch_timer, switch_buffer_timer, flags, buf);
- buf->switch_timer.expires = jiffies + chan->switch_timer_interval;
-
- 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;
-}
-
-/*
- * Called with ring_buffer_nohz_lock held for per-cpu buffers.
- */
-static void lib_ring_buffer_stop_switch_timer(struct lib_ring_buffer *buf)
-{
- struct channel *chan = buf->backend.chan;
-
- if (!chan->switch_timer_interval || !buf->switch_timer_enabled)
- return;
-
- del_timer_sync(&buf->switch_timer);
- buf->switch_timer_enabled = 0;
-}
-
-/*
- * Polling timer to check the channels for data.
- */
-static void read_buffer_timer(LTTNG_TIMER_FUNC_ARG_TYPE t)
-{
- struct lib_ring_buffer *buf = lttng_from_timer(buf, t, read_timer);
- struct channel *chan = buf->backend.chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- CHAN_WARN_ON(chan, !buf->backend.allocated);
-
- if (atomic_long_read(&buf->active_readers)
- && lib_ring_buffer_poll_deliver(config, buf, chan)) {
- wake_up_interruptible(&buf->read_wait);
- wake_up_interruptible(&chan->read_wait);
- }
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- lttng_mod_timer_pinned(&buf->read_timer,
- jiffies + chan->read_timer_interval);
- else
- mod_timer(&buf->read_timer,
- jiffies + chan->read_timer_interval);
-}
-
-/*
- * Called with ring_buffer_nohz_lock held for per-cpu buffers.
- */
-static void lib_ring_buffer_start_read_timer(struct lib_ring_buffer *buf)
-{
- struct channel *chan = buf->backend.chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- unsigned int flags = 0;
-
- if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER
- || !chan->read_timer_interval
- || buf->read_timer_enabled)
- return;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- flags = LTTNG_TIMER_PINNED;
-
- lttng_timer_setup(&buf->read_timer, read_buffer_timer, flags, buf);
- buf->read_timer.expires = jiffies + chan->read_timer_interval;
-
- 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;
-}
-
-/*
- * Called with ring_buffer_nohz_lock held for per-cpu buffers.
- */
-static void lib_ring_buffer_stop_read_timer(struct lib_ring_buffer *buf)
-{
- struct channel *chan = buf->backend.chan;
- const struct 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;
-
- 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)) {
- wake_up_interruptible(&buf->read_wait);
- wake_up_interruptible(&chan->read_wait);
- }
- buf->read_timer_enabled = 0;
-}
-
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
-
-enum cpuhp_state lttng_rb_hp_prepare;
-enum cpuhp_state lttng_rb_hp_online;
-
-void lttng_rb_set_hp_prepare(enum cpuhp_state val)
-{
- lttng_rb_hp_prepare = val;
-}
-EXPORT_SYMBOL_GPL(lttng_rb_set_hp_prepare);
-
-void lttng_rb_set_hp_online(enum cpuhp_state val)
-{
- lttng_rb_hp_online = val;
-}
-EXPORT_SYMBOL_GPL(lttng_rb_set_hp_online);
-
-int lttng_cpuhp_rb_frontend_dead(unsigned int cpu,
- struct lttng_cpuhp_node *node)
-{
- struct channel *chan = container_of(node, struct channel,
- cpuhp_prepare);
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, cpu);
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- CHAN_WARN_ON(chan, config->alloc == RING_BUFFER_ALLOC_GLOBAL);
-
- /*
- * Performing a buffer switch on a remote CPU. Performed by
- * the CPU responsible for doing the hotunplug after the target
- * CPU stopped running completely. Ensures that all data
- * from that remote CPU is flushed.
- */
- lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE);
- return 0;
-}
-EXPORT_SYMBOL_GPL(lttng_cpuhp_rb_frontend_dead);
-
-int lttng_cpuhp_rb_frontend_online(unsigned int cpu,
- struct lttng_cpuhp_node *node)
-{
- struct channel *chan = container_of(node, struct channel,
- cpuhp_online);
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, cpu);
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- CHAN_WARN_ON(chan, config->alloc == RING_BUFFER_ALLOC_GLOBAL);
-
- wake_up_interruptible(&chan->hp_wait);
- lib_ring_buffer_start_switch_timer(buf);
- lib_ring_buffer_start_read_timer(buf);
- return 0;
-}
-EXPORT_SYMBOL_GPL(lttng_cpuhp_rb_frontend_online);
-
-int lttng_cpuhp_rb_frontend_offline(unsigned int cpu,
- struct lttng_cpuhp_node *node)
-{
- struct channel *chan = container_of(node, struct channel,
- cpuhp_online);
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, cpu);
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- CHAN_WARN_ON(chan, config->alloc == RING_BUFFER_ALLOC_GLOBAL);
-
- lib_ring_buffer_stop_switch_timer(buf);
- lib_ring_buffer_stop_read_timer(buf);
- return 0;
-}
-EXPORT_SYMBOL_GPL(lttng_cpuhp_rb_frontend_offline);
-
-#else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
-
-#ifdef CONFIG_HOTPLUG_CPU
-
-/**
- * lib_ring_buffer_cpu_hp_callback - CPU hotplug callback
- * @nb: notifier block
- * @action: hotplug action to take
- * @hcpu: CPU number
- *
- * Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
- */
-static
-int lib_ring_buffer_cpu_hp_callback(struct notifier_block *nb,
- unsigned long action,
- void *hcpu)
-{
- unsigned int cpu = (unsigned long)hcpu;
- struct channel *chan = container_of(nb, struct channel,
- cpu_hp_notifier);
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, cpu);
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- if (!chan->cpu_hp_enable)
- return NOTIFY_DONE;
-
- CHAN_WARN_ON(chan, config->alloc == RING_BUFFER_ALLOC_GLOBAL);
-
- switch (action) {
- case CPU_DOWN_FAILED:
- case CPU_DOWN_FAILED_FROZEN:
- case CPU_ONLINE:
- case CPU_ONLINE_FROZEN:
- wake_up_interruptible(&chan->hp_wait);
- lib_ring_buffer_start_switch_timer(buf);
- lib_ring_buffer_start_read_timer(buf);
- return NOTIFY_OK;
-
- case CPU_DOWN_PREPARE:
- case CPU_DOWN_PREPARE_FROZEN:
- lib_ring_buffer_stop_switch_timer(buf);
- lib_ring_buffer_stop_read_timer(buf);
- return NOTIFY_OK;
-
- case CPU_DEAD:
- case CPU_DEAD_FROZEN:
- /*
- * Performing a buffer switch on a remote CPU. Performed by
- * the CPU responsible for doing the hotunplug after the target
- * CPU stopped running completely. Ensures that all data
- * from that remote CPU is flushed.
- */
- lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE);
- return NOTIFY_OK;
-
- default:
- return NOTIFY_DONE;
- }
-}
-
-#endif
-
-#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
-
-#if defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER)
-/*
- * For per-cpu buffers, call the reader wakeups before switching the buffer, so
- * that wake-up-tracing generated events are flushed before going idle (in
- * tick_nohz). We test if the spinlock is locked to deal with the race where
- * readers try to sample the ring buffer before we perform the switch. We let
- * the readers retry in that case. If there is data in the buffer, the wake up
- * is going to forbid the CPU running the reader thread from going idle.
- */
-static int notrace ring_buffer_tick_nohz_callback(struct notifier_block *nb,
- unsigned long val,
- void *data)
-{
- struct channel *chan = container_of(nb, struct channel,
- tick_nohz_notifier);
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- struct lib_ring_buffer *buf;
- int cpu = smp_processor_id();
-
- if (config->alloc != RING_BUFFER_ALLOC_PER_CPU) {
- /*
- * We don't support keeping the system idle with global buffers
- * and streaming active. In order to do so, we would need to
- * sample a non-nohz-cpumask racelessly with the nohz updates
- * without adding synchronization overhead to nohz. Leave this
- * use-case out for now.
- */
- return 0;
- }
-
- buf = channel_get_ring_buffer(config, chan, cpu);
- switch (val) {
- case TICK_NOHZ_FLUSH:
- raw_spin_lock(&buf->raw_tick_nohz_spinlock);
- if (config->wakeup == RING_BUFFER_WAKEUP_BY_TIMER
- && chan->read_timer_interval
- && atomic_long_read(&buf->active_readers)
- && (lib_ring_buffer_poll_deliver(config, buf, chan)
- || lib_ring_buffer_pending_data(config, buf, chan))) {
- wake_up_interruptible(&buf->read_wait);
- wake_up_interruptible(&chan->read_wait);
- }
- if (chan->switch_timer_interval)
- lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE);
- raw_spin_unlock(&buf->raw_tick_nohz_spinlock);
- break;
- case TICK_NOHZ_STOP:
- spin_lock(lttng_this_cpu_ptr(&ring_buffer_nohz_lock));
- lib_ring_buffer_stop_switch_timer(buf);
- lib_ring_buffer_stop_read_timer(buf);
- spin_unlock(lttng_this_cpu_ptr(&ring_buffer_nohz_lock));
- break;
- case TICK_NOHZ_RESTART:
- spin_lock(lttng_this_cpu_ptr(&ring_buffer_nohz_lock));
- lib_ring_buffer_start_read_timer(buf);
- lib_ring_buffer_start_switch_timer(buf);
- spin_unlock(lttng_this_cpu_ptr(&ring_buffer_nohz_lock));
- break;
- }
-
- return 0;
-}
-
-void notrace lib_ring_buffer_tick_nohz_flush(void)
-{
- atomic_notifier_call_chain(&tick_nohz_notifier, TICK_NOHZ_FLUSH,
- NULL);
-}
-
-void notrace lib_ring_buffer_tick_nohz_stop(void)
-{
- atomic_notifier_call_chain(&tick_nohz_notifier, TICK_NOHZ_STOP,
- NULL);
-}
-
-void notrace lib_ring_buffer_tick_nohz_restart(void)
-{
- atomic_notifier_call_chain(&tick_nohz_notifier, TICK_NOHZ_RESTART,
- NULL);
-}
-#endif /* defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER) */
-
-/*
- * Holds CPU hotplug.
- */
-static void channel_unregister_notifiers(struct channel *chan)
-{
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- channel_iterator_unregister_notifiers(chan);
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
-#ifdef CONFIG_NO_HZ
- /*
- * Remove the nohz notifier first, so we are certain we stop
- * the timers.
- */
- atomic_notifier_chain_unregister(&tick_nohz_notifier,
- &chan->tick_nohz_notifier);
- /*
- * ring_buffer_nohz_lock will not be needed below, because
- * we just removed the notifiers, which were the only source of
- * concurrency.
- */
-#endif /* CONFIG_NO_HZ */
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
- {
- int ret;
-
- ret = cpuhp_state_remove_instance(lttng_rb_hp_online,
- &chan->cpuhp_online.node);
- WARN_ON(ret);
- ret = cpuhp_state_remove_instance_nocalls(lttng_rb_hp_prepare,
- &chan->cpuhp_prepare.node);
- WARN_ON(ret);
- }
-#else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
- {
- int cpu;
-
-#ifdef CONFIG_HOTPLUG_CPU
- get_online_cpus();
- chan->cpu_hp_enable = 0;
- for_each_online_cpu(cpu) {
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
- cpu);
- lib_ring_buffer_stop_switch_timer(buf);
- lib_ring_buffer_stop_read_timer(buf);
- }
- put_online_cpus();
- unregister_cpu_notifier(&chan->cpu_hp_notifier);
-#else
- for_each_possible_cpu(cpu) {
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
- cpu);
- lib_ring_buffer_stop_switch_timer(buf);
- lib_ring_buffer_stop_read_timer(buf);
- }
-#endif
- }
-#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
- } else {
- struct lib_ring_buffer *buf = chan->backend.buf;
-
- lib_ring_buffer_stop_switch_timer(buf);
- lib_ring_buffer_stop_read_timer(buf);
- }
- channel_backend_unregister_notifiers(&chan->backend);
-}
-
-static void lib_ring_buffer_set_quiescent(struct lib_ring_buffer *buf)
-{
- if (!buf->quiescent) {
- buf->quiescent = true;
- _lib_ring_buffer_switch_remote(buf, SWITCH_FLUSH);
- }
-}
-
-static void lib_ring_buffer_clear_quiescent(struct lib_ring_buffer *buf)
-{
- buf->quiescent = false;
-}
-
-void lib_ring_buffer_set_quiescent_channel(struct channel *chan)
-{
- int cpu;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
- get_online_cpus();
- for_each_channel_cpu(cpu, chan) {
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
- cpu);
-
- lib_ring_buffer_set_quiescent(buf);
- }
- put_online_cpus();
- } else {
- struct lib_ring_buffer *buf = chan->backend.buf;
-
- lib_ring_buffer_set_quiescent(buf);
- }
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_set_quiescent_channel);
-
-void lib_ring_buffer_clear_quiescent_channel(struct channel *chan)
-{
- int cpu;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
- get_online_cpus();
- for_each_channel_cpu(cpu, chan) {
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
- cpu);
-
- lib_ring_buffer_clear_quiescent(buf);
- }
- put_online_cpus();
- } else {
- struct lib_ring_buffer *buf = chan->backend.buf;
-
- lib_ring_buffer_clear_quiescent(buf);
- }
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_clear_quiescent_channel);
-
-static void channel_free(struct channel *chan)
-{
- if (chan->backend.release_priv_ops) {
- chan->backend.release_priv_ops(chan->backend.priv_ops);
- }
- channel_iterator_free(chan);
- channel_backend_free(&chan->backend);
- kfree(chan);
-}
-
-/**
- * channel_create - Create channel.
- * @config: ring buffer instance configuration
- * @name: name of the channel
- * @priv: ring buffer client 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 channel *channel_create(const struct lib_ring_buffer_config *config,
- const char *name, void *priv, void *buf_addr,
- size_t subbuf_size,
- size_t num_subbuf, unsigned int switch_timer_interval,
- unsigned int read_timer_interval)
-{
- int ret;
- struct channel *chan;
-
- if (lib_ring_buffer_check_config(config, switch_timer_interval,
- read_timer_interval))
- return NULL;
-
- chan = kzalloc(sizeof(struct channel), GFP_KERNEL);
- if (!chan)
- return NULL;
-
- ret = channel_backend_init(&chan->backend, name, config, priv,
- subbuf_size, num_subbuf);
- if (ret)
- goto error;
-
- ret = channel_iterator_init(chan);
- if (ret)
- goto error_free_backend;
-
- chan->commit_count_mask = (~0UL >> chan->backend.num_subbuf_order);
- chan->switch_timer_interval = usecs_to_jiffies(switch_timer_interval);
- chan->read_timer_interval = usecs_to_jiffies(read_timer_interval);
- kref_init(&chan->ref);
- init_waitqueue_head(&chan->read_wait);
- init_waitqueue_head(&chan->hp_wait);
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
- chan->cpuhp_prepare.component = LTTNG_RING_BUFFER_FRONTEND;
- ret = cpuhp_state_add_instance_nocalls(lttng_rb_hp_prepare,
- &chan->cpuhp_prepare.node);
- if (ret)
- goto cpuhp_prepare_error;
-
- chan->cpuhp_online.component = LTTNG_RING_BUFFER_FRONTEND;
- ret = cpuhp_state_add_instance(lttng_rb_hp_online,
- &chan->cpuhp_online.node);
- if (ret)
- goto cpuhp_online_error;
-#else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
- {
- int 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.
- */
-#ifdef CONFIG_HOTPLUG_CPU
- chan->cpu_hp_notifier.notifier_call =
- lib_ring_buffer_cpu_hp_callback;
- chan->cpu_hp_notifier.priority = 6;
- register_cpu_notifier(&chan->cpu_hp_notifier);
-
- get_online_cpus();
- for_each_online_cpu(cpu) {
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
- cpu);
- spin_lock(&per_cpu(ring_buffer_nohz_lock, cpu));
- lib_ring_buffer_start_switch_timer(buf);
- lib_ring_buffer_start_read_timer(buf);
- spin_unlock(&per_cpu(ring_buffer_nohz_lock, cpu));
- }
- chan->cpu_hp_enable = 1;
- put_online_cpus();
-#else
- for_each_possible_cpu(cpu) {
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
- cpu);
- spin_lock(&per_cpu(ring_buffer_nohz_lock, cpu));
- lib_ring_buffer_start_switch_timer(buf);
- lib_ring_buffer_start_read_timer(buf);
- spin_unlock(&per_cpu(ring_buffer_nohz_lock, cpu));
- }
-#endif
- }
-#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
-
-#if defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER)
- /* Only benefit from NO_HZ idle with per-cpu buffers for now. */
- chan->tick_nohz_notifier.notifier_call =
- ring_buffer_tick_nohz_callback;
- chan->tick_nohz_notifier.priority = ~0U;
- atomic_notifier_chain_register(&tick_nohz_notifier,
- &chan->tick_nohz_notifier);
-#endif /* defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER) */
-
- } else {
- struct lib_ring_buffer *buf = chan->backend.buf;
-
- lib_ring_buffer_start_switch_timer(buf);
- lib_ring_buffer_start_read_timer(buf);
- }
-
- return chan;
-
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
-cpuhp_online_error:
- ret = cpuhp_state_remove_instance_nocalls(lttng_rb_hp_prepare,
- &chan->cpuhp_prepare.node);
- WARN_ON(ret);
-cpuhp_prepare_error:
-#endif /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
-error_free_backend:
- channel_backend_free(&chan->backend);
-error:
- kfree(chan);
- return NULL;
-}
-EXPORT_SYMBOL_GPL(channel_create);
-
-static
-void channel_release(struct kref *kref)
-{
- struct channel *chan = container_of(kref, struct channel, ref);
- channel_free(chan);
-}
-
-/**
- * channel_destroy - Finalize, wait for q.s. and destroy channel.
- * @chan: channel to destroy
- *
- * Holds cpu hotplug.
- * Call "destroy" callback, finalize channels, and then 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. Returns the private
- * data pointer.
- */
-void *channel_destroy(struct channel *chan)
-{
- int cpu;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- void *priv;
-
- channel_unregister_notifiers(chan);
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
- /*
- * No need to hold cpu hotplug, because all notifiers have been
- * unregistered.
- */
- for_each_channel_cpu(cpu, chan) {
- struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
- cpu);
-
- if (config->cb.buffer_finalize)
- config->cb.buffer_finalize(buf,
- chan->backend.priv,
- cpu);
- /*
- * Perform flush before writing to finalized.
- */
- smp_wmb();
- WRITE_ONCE(buf->finalized, 1);
- wake_up_interruptible(&buf->read_wait);
- }
- } else {
- struct lib_ring_buffer *buf = chan->backend.buf;
-
- if (config->cb.buffer_finalize)
- config->cb.buffer_finalize(buf, chan->backend.priv, -1);
- /*
- * Perform flush before writing to finalized.
- */
- smp_wmb();
- WRITE_ONCE(buf->finalized, 1);
- wake_up_interruptible(&buf->read_wait);
- }
- WRITE_ONCE(chan->finalized, 1);
- wake_up_interruptible(&chan->hp_wait);
- wake_up_interruptible(&chan->read_wait);
- priv = chan->backend.priv;
- kref_put(&chan->ref, channel_release);
- return priv;
-}
-EXPORT_SYMBOL_GPL(channel_destroy);
-
-struct lib_ring_buffer *channel_get_ring_buffer(
- const struct lib_ring_buffer_config *config,
- struct channel *chan, int cpu)
-{
- if (config->alloc == RING_BUFFER_ALLOC_GLOBAL)
- return chan->backend.buf;
- else
- return per_cpu_ptr(chan->backend.buf, cpu);
-}
-EXPORT_SYMBOL_GPL(channel_get_ring_buffer);
-
-int lib_ring_buffer_open_read(struct lib_ring_buffer *buf)
-{
- struct channel *chan = buf->backend.chan;
-
- if (!atomic_long_add_unless(&buf->active_readers, 1, 1))
- return -EBUSY;
- if (!lttng_kref_get(&chan->ref)) {
- atomic_long_dec(&buf->active_readers);
- return -EOVERFLOW;
- }
- lttng_smp_mb__after_atomic();
- return 0;
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_open_read);
-
-void lib_ring_buffer_release_read(struct lib_ring_buffer *buf)
-{
- struct channel *chan = buf->backend.chan;
-
- CHAN_WARN_ON(chan, atomic_long_read(&buf->active_readers) != 1);
- lttng_smp_mb__before_atomic();
- atomic_long_dec(&buf->active_readers);
- kref_put(&chan->ref, channel_release);
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_release_read);
-
-/*
- * Promote compiler barrier to a smp_mb().
- * For the specific ring buffer case, this IPI call should be removed if the
- * architecture does not reorder writes. This should eventually be provided by
- * a separate architecture-specific infrastructure.
- */
-static void remote_mb(void *info)
-{
- smp_mb();
-}
-
-/**
- * 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.
- * Busy-loop trying to get data if the tick_nohz sequence lock is held.
- */
-
-int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
- unsigned long *consumed, unsigned long *produced)
-{
- struct channel *chan = buf->backend.chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long consumed_cur, write_offset;
- int finalized;
-
-retry:
- finalized = READ_ONCE(buf->finalized);
- /*
- * Read finalized before counters.
- */
- smp_rmb();
- consumed_cur = atomic_long_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 if (raw_spin_is_locked(&buf->raw_tick_nohz_spinlock))
- goto retry;
- else
- return -EAGAIN;
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_snapshot);
-
-/**
- * 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 lib_ring_buffer *buf,
- unsigned long *consumed, unsigned long *produced)
-{
- struct channel *chan = buf->backend.chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- smp_rmb();
- *consumed = atomic_long_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_put_snapshot - move consumed counter forward
- *
- * Should only be called from consumer context.
- * @buf: ring buffer
- * @consumed_new: new consumed count value
- */
-void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
- unsigned long consumed_new)
-{
- struct lib_ring_buffer_backend *bufb = &buf->backend;
- struct channel *chan = bufb->chan;
- unsigned long consumed;
-
- CHAN_WARN_ON(chan, atomic_long_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 = atomic_long_read(&buf->consumed);
- while ((long) consumed - (long) consumed_new < 0)
- consumed = atomic_long_cmpxchg(&buf->consumed, consumed,
- consumed_new);
- /* Wake-up the metadata producer */
- wake_up_interruptible(&buf->write_wait);
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_move_consumer);
-
-#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
-static void lib_ring_buffer_flush_read_subbuf_dcache(
- const struct lib_ring_buffer_config *config,
- struct channel *chan,
- struct lib_ring_buffer *buf)
-{
- struct lib_ring_buffer_backend_pages *pages;
- unsigned long sb_bindex, id, i, nr_pages;
-
- if (config->output != RING_BUFFER_MMAP)
- return;
-
- /*
- * Architectures with caches aliased on virtual addresses may
- * use different cache lines for the linear mapping vs
- * user-space memory mapping. Given that the ring buffer is
- * based on the kernel linear mapping, aligning it with the
- * user-space mapping is not straightforward, and would require
- * extra TLB entries. Therefore, simply flush the dcache for the
- * entire sub-buffer before reading it.
- */
- id = buf->backend.buf_rsb.id;
- sb_bindex = subbuffer_id_get_index(config, id);
- pages = buf->backend.array[sb_bindex];
- nr_pages = buf->backend.num_pages_per_subbuf;
- for (i = 0; i < nr_pages; i++) {
- struct lib_ring_buffer_backend_page *backend_page;
-
- backend_page = &pages->p[i];
- flush_dcache_page(pfn_to_page(backend_page->pfn));
- }
-}
-#else
-static void lib_ring_buffer_flush_read_subbuf_dcache(
- const struct lib_ring_buffer_config *config,
- struct channel *chan,
- struct lib_ring_buffer *buf)
-{
-}
-#endif
-
-/**
- * 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.
- * Busy-loop trying to get data if the tick_nohz sequence lock is held.
- */
-int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf,
- unsigned long consumed)
-{
- struct channel *chan = buf->backend.chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long consumed_cur, consumed_idx, commit_count, write_offset;
- int ret;
- int finalized;
-
- if (buf->get_subbuf) {
- /*
- * Reader is trying to get a subbuffer twice.
- */
- CHAN_WARN_ON(chan, 1);
- return -EBUSY;
- }
-retry:
- finalized = READ_ONCE(buf->finalized);
- /*
- * Read finalized before counters.
- */
- smp_rmb();
- consumed_cur = atomic_long_read(&buf->consumed);
- consumed_idx = subbuf_index(consumed, chan);
- commit_count = v_read(config, &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.
- * smp_call_function_single can fail if the remote CPU is offline,
- * this is OK because then there is no wmb to execute there.
- * If our thread is executing on the same CPU as the on the buffers
- * belongs to, we don't have to synchronize it at all. If we are
- * migrated, the scheduler will take care of the memory barriers.
- * Normally, smp_call_function_single() should ensure program order when
- * executing the remote function, which implies that it surrounds the
- * function execution with :
- * smp_mb()
- * send IPI
- * csd_lock_wait
- * recv IPI
- * smp_mb()
- * exec. function
- * smp_mb()
- * csd unlock
- * smp_mb()
- *
- * However, smp_call_function_single() does not seem to clearly execute
- * such barriers. It depends on spinlock semantic to provide the barrier
- * before executing the IPI and, when busy-looping, csd_lock_wait only
- * executes smp_mb() when it has to wait for the other CPU.
- *
- * I don't trust this code. Therefore, let's add the smp_mb() sequence
- * required ourself, even if duplicated. It has no performance impact
- * anyway.
- *
- * smp_mb() is needed because smp_rmb() and smp_wmb() only order read vs
- * read and write vs write. They do not ensure core synchronization. We
- * really have to ensure total order between the 3 barriers running on
- * the 2 CPUs.
- */
- if (config->ipi == RING_BUFFER_IPI_BARRIER) {
- if (config->sync == RING_BUFFER_SYNC_PER_CPU
- && config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
- if (raw_smp_processor_id() != buf->backend.cpu) {
- /* Total order with IPI handler smp_mb() */
- smp_mb();
- smp_call_function_single(buf->backend.cpu,
- remote_mb, NULL, 1);
- /* Total order with IPI handler smp_mb() */
- smp_mb();
- }
- } else {
- /* Total order with IPI handler smp_mb() */
- smp_mb();
- smp_call_function(remote_mb, NULL, 1);
- /* Total order with IPI handler smp_mb() */
- smp_mb();
- }
- } else {
- /*
- * Local rmb to match the remote wmb to read the commit count
- * before the buffer data and the write offset.
- */
- 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, 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, 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));
- if (ret)
- goto retry;
- subbuffer_id_clear_noref(config, &buf->backend.buf_rsb.id);
-
- buf->get_subbuf_consumed = consumed;
- buf->get_subbuf = 1;
-
- lib_ring_buffer_flush_read_subbuf_dcache(config, chan, buf);
-
- 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 if (raw_spin_is_locked(&buf->raw_tick_nohz_spinlock))
- goto retry;
- else
- return -EAGAIN;
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_get_subbuf);
-
-/**
- * lib_ring_buffer_put_subbuf - release exclusive subbuffer access
- * @buf: ring buffer
- */
-void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf)
-{
- struct lib_ring_buffer_backend *bufb = &buf->backend;
- struct channel *chan = bufb->chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long read_sb_bindex, consumed_idx, consumed;
-
- CHAN_WARN_ON(chan, atomic_long_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.
- */
- read_sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
- v_add(config, v_read(config,
- &bufb->array[read_sb_bindex]->records_unread),
- &bufb->records_read);
- v_set(config, &bufb->array[read_sb_bindex]->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));
- /*
- * update_read_sb_index return value ignored. Don't exchange sub-buffer
- * if the writer concurrently updated it.
- */
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_put_subbuf);
-
-/*
- * 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 lib_ring_buffer *buf,
- struct channel *chan,
- unsigned long cons_offset,
- int cpu)
-{
- const struct 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, &buf->commit_hot[cons_idx].cc);
- commit_count_sb = v_read(config, &buf->commit_cold[cons_idx].cc_sb);
-
- if (subbuf_offset(commit_count, chan) != 0)
- printk(KERN_WARNING
- "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);
-
- printk(KERN_DEBUG "ring buffer: %s, cpu %d: %lu bytes committed\n",
- chan->backend.name, cpu, commit_count);
-}
-
-static
-void lib_ring_buffer_print_buffer_errors(struct lib_ring_buffer *buf,
- struct channel *chan,
- void *priv, int cpu)
-{
- const struct 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 = atomic_long_read(&buf->consumed);
- if (write_offset != cons_offset)
- printk(KERN_DEBUG
- "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 = atomic_long_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);
-}
-
-#ifdef LTTNG_RING_BUFFER_COUNT_EVENTS
-static
-void lib_ring_buffer_print_records_count(struct channel *chan,
- struct lib_ring_buffer *buf,
- int cpu)
-{
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- if (!strcmp(chan->backend.name, "relay-metadata")) {
- printk(KERN_DEBUG "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 {
- printk(KERN_DEBUG "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));
- }
-}
-#else
-static
-void lib_ring_buffer_print_records_count(struct channel *chan,
- struct lib_ring_buffer *buf,
- int cpu)
-{
-}
-#endif
-
-static
-void lib_ring_buffer_print_errors(struct channel *chan,
- struct lib_ring_buffer *buf, int cpu)
-{
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- void *priv = chan->backend.priv;
-
- lib_ring_buffer_print_records_count(chan, buf, cpu);
- if (strcmp(chan->backend.name, "relay-metadata")) {
- if (v_read(config, &buf->records_lost_full)
- || v_read(config, &buf->records_lost_wrap)
- || v_read(config, &buf->records_lost_big))
- printk(KERN_WARNING
- "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);
-}
-
-/*
- * 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 lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- u64 tsc)
-{
- const struct 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);
-
- /*
- * Order all writes to buffer before the commit count update that will
- * determine that the subbuffer is full.
- */
- if (config->ipi == RING_BUFFER_IPI_BARRIER) {
- /*
- * Must write slot data before incrementing commit count. This
- * compiler barrier is upgraded into a smp_mb() by the IPI sent
- * by get_subbuf().
- */
- barrier();
- } else
- smp_wmb();
- cc_hot = &buf->commit_hot[oldidx];
- 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, tsc);
- lib_ring_buffer_write_commit_counter(config, buf, chan,
- offsets->old + config->cb.subbuffer_header_size(),
- commit_count, 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 lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- u64 tsc)
-{
- const struct 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;
- u64 *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);
-
- ts_end = &buf->ts_end[oldidx];
- /*
- * 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.
- */
- if (config->ipi == RING_BUFFER_IPI_BARRIER) {
- /*
- * Must write slot data before incrementing commit count. This
- * compiler barrier is upgraded into a smp_mb() by the IPI sent
- * by get_subbuf().
- */
- barrier();
- } else
- smp_wmb();
- cc_hot = &buf->commit_hot[oldidx];
- 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, tsc);
- lib_ring_buffer_write_commit_counter(config, buf, chan,
- offsets->old + padding_size, commit_count,
- 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 lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- u64 tsc)
-{
- const struct 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);
-
- /*
- * Order all writes to buffer before the commit count update that will
- * determine that the subbuffer is full.
- */
- if (config->ipi == RING_BUFFER_IPI_BARRIER) {
- /*
- * Must write slot data before incrementing commit count. This
- * compiler barrier is upgraded into a smp_mb() by the IPI sent
- * by get_subbuf().
- */
- barrier();
- } else
- smp_wmb();
- cc_hot = &buf->commit_hot[beginidx];
- 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, tsc);
- lib_ring_buffer_write_commit_counter(config, buf, chan,
- offsets->begin + config->cb.subbuffer_header_size(),
- commit_count, 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 lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- u64 tsc)
-{
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long endidx, data_size;
- u64 *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);
- ts_end = &buf->ts_end[endidx];
- /*
- * 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 lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- u64 *tsc)
-{
- const struct 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 and CPU tick_nohz stop
- * 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 (unlikely(off == 0)) {
- unsigned long sb_index, commit_count;
-
- /*
- * We are performing a SWITCH_FLUSH. At this stage, there are no
- * concurrent writes into the buffer.
- *
- * 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;
-
- /* Test new buffer integrity */
- sb_index = subbuf_index(offsets->begin, chan);
- commit_count = v_read(config,
- &buf->commit_cold[sb_index].cc_sb);
- reserve_commit_diff =
- (buf_trunc(offsets->begin, chan)
- >> chan->backend.num_subbuf_order)
- - (commit_count & chan->commit_count_mask);
- if (likely(reserve_commit_diff == 0)) {
- /* Next subbuffer not being written to. */
- if (unlikely(config->mode != RING_BUFFER_OVERWRITE &&
- subbuf_trunc(offsets->begin, chan)
- - subbuf_trunc((unsigned long)
- atomic_long_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.
- *
- * 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 lib_ring_buffer *buf, enum switch_mode mode)
-{
- struct channel *chan = buf->backend.chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- struct switch_offsets offsets;
- unsigned long oldidx;
- u64 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);
-
- /*
- * May need to populate header start on SWITCH_FLUSH.
- */
- if (offsets.switch_old_start) {
- lib_ring_buffer_switch_old_start(buf, chan, &offsets, tsc);
- offsets.old += config->cb.subbuffer_header_size();
- }
-
- /*
- * Switch old subbuffer.
- */
- lib_ring_buffer_switch_old_end(buf, chan, &offsets, tsc);
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_switch_slow);
-
-struct switch_param {
- struct lib_ring_buffer *buf;
- enum switch_mode mode;
-};
-
-static void remote_switch(void *info)
-{
- struct switch_param *param = info;
- struct lib_ring_buffer *buf = param->buf;
-
- lib_ring_buffer_switch_slow(buf, param->mode);
-}
-
-static void _lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf,
- enum switch_mode mode)
-{
- struct channel *chan = buf->backend.chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- int ret;
- struct switch_param param;
-
- /*
- * With global synchronization we don't need to use the IPI scheme.
- */
- if (config->sync == RING_BUFFER_SYNC_GLOBAL) {
- lib_ring_buffer_switch_slow(buf, mode);
- return;
- }
-
- /*
- * Disabling preemption ensures two things: first, that the
- * target cpu is not taken concurrently offline while we are within
- * smp_call_function_single(). Secondly, if it happens that the
- * CPU is not online, our own call to lib_ring_buffer_switch_slow()
- * needs to be protected from CPU hotplug handlers, which can
- * also perform a remote subbuffer switch.
- */
- preempt_disable();
- param.buf = buf;
- param.mode = mode;
- ret = smp_call_function_single(buf->backend.cpu,
- remote_switch, ¶m, 1);
- if (ret) {
- /* Remote CPU is offline, do it ourself. */
- lib_ring_buffer_switch_slow(buf, mode);
- }
- preempt_enable();
-}
-
-/* Switch sub-buffer if current sub-buffer is non-empty. */
-void lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf)
-{
- _lib_ring_buffer_switch_remote(buf, SWITCH_ACTIVE);
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_switch_remote);
-
-/* Switch sub-buffer even if current sub-buffer is empty. */
-void lib_ring_buffer_switch_remote_empty(struct lib_ring_buffer *buf)
-{
- _lib_ring_buffer_switch_remote(buf, SWITCH_FLUSH);
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_switch_remote_empty);
-
-void lib_ring_buffer_clear(struct lib_ring_buffer *buf)
-{
- struct lib_ring_buffer_backend *bufb = &buf->backend;
- struct channel *chan = bufb->chan;
-
- lib_ring_buffer_switch_remote(buf);
- lib_ring_buffer_clear_reader(buf, chan);
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_clear);
-
-/*
- * 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 lib_ring_buffer *buf,
- struct channel *chan,
- struct switch_offsets *offsets,
- struct lib_ring_buffer_ctx *ctx,
- void *client_ctx)
-{
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- unsigned long reserve_commit_diff, offset_cmp;
-
-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 (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 (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 (unlikely(offsets->switch_new_start)) {
- unsigned long sb_index, commit_count;
-
- /*
- * We are typically not filling the previous buffer completely.
- */
- if (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.
- */
- smp_rmb();
- commit_count = v_read(config,
- &buf->commit_cold[sb_index].cc_sb);
- /* Read buf->commit_cold[sb_index].cc_sb before buf->offset. */
- smp_rmb();
- if (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 (likely(reserve_commit_diff == 0)) {
- /* Next subbuffer not being written to. */
- if (unlikely(config->mode != RING_BUFFER_OVERWRITE &&
- subbuf_trunc(offsets->begin, chan)
- - subbuf_trunc((unsigned long)
- atomic_long_read(&buf->consumed), chan)
- >= chan->backend.buf_size)) {
- /*
- * We do not overwrite non consumed buffers
- * and we are full : record is lost.
- */
- v_inc(config, &buf->records_lost_full);
- 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 {
- /*
- * 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.
- */
- v_inc(config, &buf->records_lost_wrap);
- 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 (unlikely(subbuf_offset(offsets->begin, chan)
- + offsets->size > chan->backend.subbuf_size)) {
- /*
- * Record too big for subbuffers, report error, don't
- * complete the sub-buffer switch.
- */
- v_inc(config, &buf->records_lost_big);
- 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 (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;
-}
-
-static struct lib_ring_buffer *get_current_buf(struct channel *chan, int cpu)
-{
- const struct lib_ring_buffer_config *config = &chan->backend.config;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- return per_cpu_ptr(chan->backend.buf, cpu);
- else
- return chan->backend.buf;
-}
-
-void lib_ring_buffer_lost_event_too_big(struct channel *chan)
-{
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- struct lib_ring_buffer *buf = get_current_buf(chan, smp_processor_id());
-
- v_inc(config, &buf->records_lost_big);
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_lost_event_too_big);
-
-/**
- * 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 lib_ring_buffer_ctx *ctx,
- void *client_ctx)
-{
- struct channel *chan = ctx->chan;
- const struct lib_ring_buffer_config *config = &chan->backend.config;
- struct lib_ring_buffer *buf;
- struct switch_offsets offsets;
- int ret;
-
- ctx->buf = buf = get_current_buf(chan, ctx->cpu);
- offsets.size = 0;
-
- do {
- ret = lib_ring_buffer_try_reserve_slow(buf, chan, &offsets,
- ctx, client_ctx);
- if (unlikely(ret))
- return ret;
- } while (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));
-
- /*
- * Switch old subbuffer if needed.
- */
- if (unlikely(offsets.switch_old_end)) {
- lib_ring_buffer_clear_noref(config, &buf->backend,
- subbuf_index(offsets.old - 1, chan));
- lib_ring_buffer_switch_old_end(buf, chan, &offsets, ctx->tsc);
- }
-
- /*
- * Populate new subbuffer.
- */
- if (unlikely(offsets.switch_new_start))
- lib_ring_buffer_switch_new_start(buf, chan, &offsets, ctx->tsc);
-
- if (unlikely(offsets.switch_new_end))
- lib_ring_buffer_switch_new_end(buf, chan, &offsets, ctx->tsc);
-
- ctx->slot_size = offsets.size;
- ctx->pre_offset = offsets.begin;
- ctx->buf_offset = offsets.begin + offsets.pre_header_padding;
- return 0;
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_reserve_slow);
-
-static
-void lib_ring_buffer_vmcore_check_deliver(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer *buf,
- unsigned long commit_count,
- unsigned long idx)
-{
- if (config->oops == RING_BUFFER_OOPS_CONSISTENCY)
- v_set(config, &buf->commit_hot[idx].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 lib_ring_buffer_config *config,
- struct lib_ring_buffer *buf,
- unsigned long idx)
-{
- v_add(config, subbuffer_get_records_count(config,
- &buf->backend, idx),
- &buf->records_count);
- v_add(config, subbuffer_count_records_overrun(config,
- &buf->backend, idx),
- &buf->records_overrun);
-}
-#else /* LTTNG_RING_BUFFER_COUNT_EVENTS */
-static
-void deliver_count_events(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer *buf,
- unsigned long idx)
-{
-}
-#endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */
-
-
-void lib_ring_buffer_check_deliver_slow(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer *buf,
- struct channel *chan,
- unsigned long offset,
- unsigned long commit_count,
- unsigned long idx,
- u64 tsc)
-{
- unsigned long old_commit_count = commit_count
- - chan->backend.subbuf_size;
-
- /*
- * 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.
- */
- smp_wmb();
- if (likely(v_cmpxchg(config, &buf->commit_cold[idx].cc_sb,
- old_commit_count, old_commit_count + 1)
- == old_commit_count)) {
- u64 *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.
- */
- smp_mb();
- ts_end = &buf->ts_end[idx];
- deliver_count_events(config, buf, idx);
- config->cb.buffer_end(buf, *ts_end, idx,
- lib_ring_buffer_get_data_size(config,
- buf,
- idx));
-
- /*
- * Increment the packet counter while we have exclusive
- * access.
- */
- subbuffer_inc_packet_count(config, &buf->backend, idx);
-
- /*
- * 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));
-
- /*
- * 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.
- */
- smp_mb();
- /* End of exclusive subbuffer access */
- v_set(config, &buf->commit_cold[idx].cc_sb,
- commit_count);
- /*
- * Order later updates to reserve count after
- * the commit_cold cc_sb update.
- */
- smp_wmb();
- lib_ring_buffer_vmcore_check_deliver(config, buf,
- commit_count, idx);
-
- /*
- * RING_BUFFER_WAKEUP_BY_WRITER wakeup is not lock-free.
- */
- if (config->wakeup == RING_BUFFER_WAKEUP_BY_WRITER
- && atomic_long_read(&buf->active_readers)
- && lib_ring_buffer_poll_deliver(config, buf, chan)) {
- wake_up_interruptible(&buf->read_wait);
- wake_up_interruptible(&chan->read_wait);
- }
-
- }
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_check_deliver_slow);
-
-int __init init_lib_ring_buffer_frontend(void)
-{
- int cpu;
-
- for_each_possible_cpu(cpu)
- spin_lock_init(&per_cpu(ring_buffer_nohz_lock, cpu));
- return 0;
-}
-
-module_init(init_lib_ring_buffer_frontend);
-
-void __exit exit_lib_ring_buffer_frontend(void)
-{
-}
-
-module_exit(exit_lib_ring_buffer_frontend);
projects / lttng-modules.git / blobdiff