+++ /dev/null
-/*
- * ring_buffer_frontend.c
- *
- * (C) Copyright 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * Ring buffer wait-free buffer synchronization. Producer-consumer and flight
- * recorder (overwrite) modes. See thesis:
- *
- * Desnoyers, Mathieu (2009), "Low-Impact Operating System Tracing", Ph.D.
- * dissertation, Ecole Polytechnique de Montreal.
- * http://www.lttng.org/pub/thesis/desnoyers-dissertation-2009-12.pdf
- *
- * - Algorithm presentation in Chapter 5:
- * "Lockless Multi-Core High-Throughput Buffering".
- * - Algorithm formal verification in Section 8.6:
- * "Formal verification of LTTng"
- *
- * Author:
- * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * Inspired from LTT and RelayFS:
- * Karim Yaghmour <karim@opersys.com>
- * Tom Zanussi <zanussi@us.ibm.com>
- * Bob Wisniewski <bob@watson.ibm.com>
- * And from K42 :
- * Bob Wisniewski <bob@watson.ibm.com>
- *
- * Buffer reader semantic :
- *
- * - get_subbuf_size
- * while buffer is not finalized and empty
- * - get_subbuf
- * - if return value != 0, continue
- * - splice one subbuffer worth of data to a pipe
- * - splice the data from pipe to disk/network
- * - put_subbuf
- *
- * Dual LGPL v2.1/GPL v2 license.
- */
-
-#include <linux/delay.h>
-#include <linux/module.h>
-#include <linux/percpu.h>
-
-#include "../../wrapper/ringbuffer/config.h"
-#include "../../wrapper/ringbuffer/backend.h"
-#include "../../wrapper/ringbuffer/frontend.h"
-#include "../../wrapper/ringbuffer/iterator.h"
-#include "../../wrapper/ringbuffer/nohz.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);
-
-/*
- * 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);
- kfree(buf->commit_hot);
- kfree(buf->commit_cold);
-
- 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);
- }
- 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;
- unsigned int num_subbuf;
- 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 =
- kzalloc_node(ALIGN(sizeof(*buf->commit_hot)
- * chan->backend.num_subbuf,
- 1 << INTERNODE_CACHE_SHIFT),
- GFP_KERNEL, cpu_to_node(max(cpu, 0)));
- if (!buf->commit_hot) {
- ret = -ENOMEM;
- goto free_chanbuf;
- }
-
- buf->commit_cold =
- kzalloc_node(ALIGN(sizeof(*buf->commit_cold)
- * chan->backend.num_subbuf,
- 1 << INTERNODE_CACHE_SHIFT),
- GFP_KERNEL, cpu_to_node(max(cpu, 0)));
- if (!buf->commit_cold) {
- ret = -ENOMEM;
- goto free_commit;
- }
-
- num_subbuf = chan->backend.num_subbuf;
- init_waitqueue_head(&buf->read_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:
- kfree(buf->commit_cold);
-free_commit:
- kfree(buf->commit_hot);
-free_chanbuf:
- lib_ring_buffer_backend_free(&buf->backend);
- return ret;
-}
-
-static void switch_buffer_timer(unsigned long data)
-{
- struct lib_ring_buffer *buf = (struct lib_ring_buffer *)data;
- 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)
- 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;
-
- if (!chan->switch_timer_interval || buf->switch_timer_enabled)
- return;
- init_timer(&buf->switch_timer);
- buf->switch_timer.function = switch_buffer_timer;
- buf->switch_timer.expires = jiffies + chan->switch_timer_interval;
- buf->switch_timer.data = (unsigned long)buf;
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- add_timer_on(&buf->switch_timer, buf->backend.cpu);
- else
- add_timer(&buf->switch_timer);
- buf->switch_timer_enabled = 1;
-}
-
-/*
- * 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(unsigned long data)
-{
- struct lib_ring_buffer *buf = (struct lib_ring_buffer *)data;
- 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)
- 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;
-
- if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER
- || !chan->read_timer_interval
- || buf->read_timer_enabled)
- return;
-
- init_timer(&buf->read_timer);
- buf->read_timer.function = read_buffer_timer;
- buf->read_timer.expires = jiffies + chan->read_timer_interval;
- buf->read_timer.data = (unsigned long)buf;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- add_timer_on(&buf->read_timer, buf->backend.cpu);
- else
- add_timer(&buf->read_timer);
- buf->read_timer_enabled = 1;
-}
-
-/*
- * 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;
-}
-
-#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 __cpuinit 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
-
-#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(&__get_cpu_var(ring_buffer_nohz_lock));
- lib_ring_buffer_stop_switch_timer(buf);
- lib_ring_buffer_stop_read_timer(buf);
- spin_unlock(&__get_cpu_var(ring_buffer_nohz_lock));
- break;
- case TICK_NOHZ_RESTART:
- spin_lock(&__get_cpu_var(ring_buffer_nohz_lock));
- lib_ring_buffer_start_read_timer(buf);
- lib_ring_buffer_start_switch_timer(buf);
- spin_unlock(&__get_cpu_var(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;
- int cpu;
-
- 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 */
-#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
- } 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 channel_free(struct channel *chan)
-{
- 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, cpu;
- 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 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) */
-
- /*
- * 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
- } 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;
-
-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, wait for readers to release their
- * reference, then destroy ring buffer data. 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);
- if (buf->backend.allocated)
- lib_ring_buffer_switch_slow(buf, SWITCH_FLUSH);
- /*
- * Perform flush before writing to finalized.
- */
- smp_wmb();
- ACCESS_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);
- if (buf->backend.allocated)
- lib_ring_buffer_switch_slow(buf, SWITCH_FLUSH);
- /*
- * Perform flush before writing to finalized.
- */
- smp_wmb();
- ACCESS_ONCE(buf->finalized) = 1;
- wake_up_interruptible(&buf->read_wait);
- }
- ACCESS_ONCE(chan->finalized) = 1;
- wake_up_interruptible(&chan->hp_wait);
- wake_up_interruptible(&chan->read_wait);
- kref_put(&chan->ref, channel_release);
- priv = chan->backend.priv;
- 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;
- kref_get(&chan->ref);
- smp_mb__after_atomic_inc();
- 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);
- smp_mb__before_atomic_dec();
- 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 = ACCESS_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);
-
-/**
- * lib_ring_buffer_put_snapshot - move consumed counter forward
- * @buf: ring buffer
- * @consumed_new: new consumed count value
- */
-void lib_ring_buffer_move_consumer(struct 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);
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_move_consumer);
-
-/**
- * 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;
-
-retry:
- finalized = ACCESS_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_cur, chan)
- >> chan->backend.num_subbuf_order)
- != 0)
- goto nodata;
-
- /*
- * Check that we are not about to read the same subbuffer in
- * which the writer head is.
- */
- if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed_cur, chan)
- == 0)
- goto nodata;
-
- /*
- * Failure to get the subbuffer causes a busy-loop retry without going
- * to a wait queue. These are caused by short-lived race windows where
- * the writer is getting access to a subbuffer we were trying to get
- * access to. Also checks that the "consumed" buffer count we are
- * looking for matches the one contained in the subbuffer id.
- */
- ret = update_read_sb_index(config, &buf->backend, &chan->backend,
- consumed_idx, buf_trunc_val(consumed, chan));
- if (ret)
- goto retry;
- subbuffer_id_clear_noref(config, &buf->backend.buf_rsb.id);
-
- buf->get_subbuf_consumed = consumed;
- buf->get_subbuf = 1;
-
- return 0;
-
-nodata:
- /*
- * The memory barriers __wait_event()/wake_up_interruptible() take care
- * of "raw_spin_is_locked" memory ordering.
- */
- if (finalized)
- return -ENODATA;
- else 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;
-
- /*
- * Can be called in the error path of allocation when
- * trans_channel_data is not yet set.
- */
- if (!chan)
- return;
- /*
- * 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_WARNING
- "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);
-}
-
-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;
-
- 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));
-
- 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;
-
- 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();
- v_add(config, config->cb.subbuffer_header_size(),
- &buf->commit_hot[oldidx].cc);
- commit_count = v_read(config, &buf->commit_hot[oldidx].cc);
- /* Check if the written buffer has to be delivered */
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->old,
- commit_count, oldidx);
- lib_ring_buffer_write_commit_counter(config, buf, chan, oldidx,
- offsets->old, commit_count,
- config->cb.subbuffer_header_size());
-}
-
-/*
- * 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;
-
- 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);
-
- /*
- * 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();
- v_add(config, padding_size, &buf->commit_hot[oldidx].cc);
- commit_count = v_read(config, &buf->commit_hot[oldidx].cc);
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->old - 1,
- commit_count, oldidx);
- lib_ring_buffer_write_commit_counter(config, buf, chan, oldidx,
- offsets->old, commit_count,
- padding_size);
-}
-
-/*
- * 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;
-
- 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();
- v_add(config, config->cb.subbuffer_header_size(),
- &buf->commit_hot[beginidx].cc);
- commit_count = v_read(config, &buf->commit_hot[beginidx].cc);
- /* Check if the written buffer has to be delivered */
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->begin,
- commit_count, beginidx);
- lib_ring_buffer_write_commit_counter(config, buf, chan, beginidx,
- offsets->begin, commit_count,
- config->cb.subbuffer_header_size());
-}
-
-/*
- * lib_ring_buffer_switch_new_end: finish switching current subbuffer
- *
- * The only remaining threads could be the ones with pending commits. They will
- * have to do the deliver themselves.
- */
-static
-void lib_ring_buffer_switch_new_end(struct 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 = subbuf_index(offsets->end - 1, chan);
- unsigned long commit_count, padding_size, data_size;
-
- data_size = subbuf_offset(offsets->end - 1, chan) + 1;
- padding_size = chan->backend.subbuf_size - data_size;
- subbuffer_set_data_size(config, &buf->backend, endidx, data_size);
-
- /*
- * 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();
- v_add(config, padding_size, &buf->commit_hot[endidx].cc);
- commit_count = v_read(config, &buf->commit_hot[endidx].cc);
- lib_ring_buffer_check_deliver(config, buf, chan, offsets->end - 1,
- commit_count, endidx);
- lib_ring_buffer_write_commit_counter(config, buf, chan, endidx,
- offsets->end, commit_count,
- padding_size);
-}
-
-/*
- * 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;
-
- 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 > 0) {
- if (unlikely(off == 0)) {
- /*
- * The client does not save any header information.
- * Don't switch empty subbuffer on finalize, because it
- * is invalid to deliver a completely empty subbuffer.
- */
- if (!config->cb.subbuffer_header_size())
- return -1;
- /*
- * Need to write the subbuffer start header on finalize.
- */
- offsets->switch_old_start = 1;
- }
- offsets->begin = subbuf_align(offsets->begin, chan);
- } else
- return -1; /* we do not have to switch : buffer is empty */
- /* Note: old points to the next subbuf at offset 0 */
- offsets->end = offsets->begin;
- return 0;
-}
-
-/*
- * Force a sub-buffer switch. This operation is completely reentrant : can be
- * called while tracing is active with absolutely no lock held.
- *
- * Note, however, that as a v_cmpxchg is used for some atomic
- * operations, this function must be called from the CPU which owns the buffer
- * for a ACTIVE flush.
- */
-void lib_ring_buffer_switch_slow(struct 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);
-
-/*
- * 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)
-{
- const struct lib_ring_buffer_config *config = chan->backend.config;
- unsigned long reserve_commit_diff;
-
- offsets->begin = v_read(config, &buf->offset);
- offsets->old = offsets->begin;
- offsets->switch_new_start = 0;
- offsets->switch_new_end = 0;
- offsets->switch_old_end = 0;
- offsets->pre_header_padding = 0;
-
- ctx->tsc = config->cb.ring_buffer_clock_read(chan);
- if ((int64_t) ctx->tsc == -EIO)
- return -EIO;
-
- if (last_tsc_overflow(config, buf, ctx->tsc))
- ctx->rflags |= RING_BUFFER_RFLAG_FULL_TSC;
-
- if (unlikely(subbuf_offset(offsets->begin, ctx->chan) == 0)) {
- offsets->switch_new_start = 1; /* For offsets->begin */
- } else {
- offsets->size = config->cb.record_header_size(config, chan,
- offsets->begin,
- &offsets->pre_header_padding,
- ctx);
- offsets->size +=
- lib_ring_buffer_align(offsets->begin + offsets->size,
- ctx->largest_align)
- + ctx->data_size;
- if (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;
-
- /*
- * 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);
- reserve_commit_diff =
- (buf_trunc(offsets->begin, chan)
- >> chan->backend.num_subbuf_order)
- - ((unsigned long) v_read(config,
- &buf->commit_cold[sb_index].cc_sb)
- & 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. 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);
- 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;
-}
-
-/**
- * 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)
-{
- 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;
-
- if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
- buf = per_cpu_ptr(chan->backend.buf, ctx->cpu);
- else
- buf = chan->backend.buf;
- ctx->buf = buf;
-
- offsets.size = 0;
-
- do {
- ret = lib_ring_buffer_try_reserve_slow(buf, chan, &offsets,
- 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);
projects / lttng-ust.git / blobdiff