#include <urcu/compiler.h>
#include <urcu/ref.h>
#include <urcu/tls-compat.h>
+#include <poll.h>
#include <helper.h>
#include "smp.h"
#include "tlsfixup.h"
#include "../liblttng-ust/compat.h" /* For ENODATA */
-#ifndef max
-#define max(a, b) ((a) > (b) ? (a) : (b))
-#endif
-
/* Print DBG() messages about events lost only every 1048576 hits */
#define DBG_PRINT_NR_LOST (1UL << 20)
#define LTTNG_UST_RB_SIG_READ SIGRTMIN + 1
#define LTTNG_UST_RB_SIG_TEARDOWN SIGRTMIN + 2
#define CLOCKID CLOCK_MONOTONIC
+#define LTTNG_UST_RING_BUFFER_GET_RETRY 10
+#define LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS 10
+
+/*
+ * Non-static to ensure the compiler does not optimize away the xor.
+ */
+uint8_t lttng_crash_magic_xor[] = RB_CRASH_DUMP_ABI_MAGIC_XOR;
/*
* Use POSIX SHM: shm_open(3) and shm_unlink(3).
void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
struct lttng_ust_shm_handle *handle)
{
- struct channel *chan = shmp(handle, buf->backend.chan);
- const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
+ struct channel *chan;
+ const struct lttng_ust_lib_ring_buffer_config *config;
unsigned int i;
+ chan = shmp(handle, buf->backend.chan);
+ if (!chan)
+ abort();
+ config = &chan->backend.config;
/*
* Reset iterator first. It will put the subbuffer if it currently holds
* it.
/* Don't reset reader reference count */
}
+static
+void init_crash_abi(const struct lttng_ust_lib_ring_buffer_config *config,
+ struct lttng_crash_abi *crash_abi,
+ struct lttng_ust_lib_ring_buffer *buf,
+ struct channel_backend *chanb,
+ struct shm_object *shmobj,
+ struct lttng_ust_shm_handle *handle)
+{
+ int i;
+
+ for (i = 0; i < RB_CRASH_DUMP_ABI_MAGIC_LEN; i++)
+ crash_abi->magic[i] = lttng_crash_magic_xor[i] ^ 0xFF;
+ crash_abi->mmap_length = shmobj->memory_map_size;
+ crash_abi->endian = RB_CRASH_ENDIAN;
+ crash_abi->major = RB_CRASH_DUMP_ABI_MAJOR;
+ crash_abi->minor = RB_CRASH_DUMP_ABI_MINOR;
+ crash_abi->word_size = sizeof(unsigned long);
+ crash_abi->layout_type = LTTNG_CRASH_TYPE_UST;
+
+ /* Offset of fields */
+ crash_abi->offset.prod_offset =
+ (uint32_t) ((char *) &buf->offset - (char *) buf);
+ crash_abi->offset.consumed_offset =
+ (uint32_t) ((char *) &buf->consumed - (char *) buf);
+ crash_abi->offset.commit_hot_array =
+ (uint32_t) ((char *) shmp(handle, buf->commit_hot) - (char *) buf);
+ crash_abi->offset.commit_hot_seq =
+ offsetof(struct commit_counters_hot, seq);
+ crash_abi->offset.buf_wsb_array =
+ (uint32_t) ((char *) shmp(handle, buf->backend.buf_wsb) - (char *) buf);
+ crash_abi->offset.buf_wsb_id =
+ offsetof(struct lttng_ust_lib_ring_buffer_backend_subbuffer, id);
+ crash_abi->offset.sb_array =
+ (uint32_t) ((char *) shmp(handle, buf->backend.array) - (char *) buf);
+ crash_abi->offset.sb_array_shmp_offset =
+ offsetof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp,
+ shmp._ref.offset);
+ crash_abi->offset.sb_backend_p_offset =
+ offsetof(struct lttng_ust_lib_ring_buffer_backend_pages,
+ p._ref.offset);
+
+ /* Field length */
+ crash_abi->length.prod_offset = sizeof(buf->offset);
+ crash_abi->length.consumed_offset = sizeof(buf->consumed);
+ crash_abi->length.commit_hot_seq =
+ sizeof(((struct commit_counters_hot *) NULL)->seq);
+ crash_abi->length.buf_wsb_id =
+ sizeof(((struct lttng_ust_lib_ring_buffer_backend_subbuffer *) NULL)->id);
+ crash_abi->length.sb_array_shmp_offset =
+ sizeof(((struct lttng_ust_lib_ring_buffer_backend_pages_shmp *) NULL)->shmp._ref.offset);
+ crash_abi->length.sb_backend_p_offset =
+ sizeof(((struct lttng_ust_lib_ring_buffer_backend_pages *) NULL)->p._ref.offset);
+
+ /* Array stride */
+ crash_abi->stride.commit_hot_array =
+ sizeof(struct commit_counters_hot);
+ crash_abi->stride.buf_wsb_array =
+ sizeof(struct lttng_ust_lib_ring_buffer_backend_subbuffer);
+ crash_abi->stride.sb_array =
+ sizeof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp);
+
+ /* Buffer constants */
+ crash_abi->buf_size = chanb->buf_size;
+ crash_abi->subbuf_size = chanb->subbuf_size;
+ crash_abi->num_subbuf = chanb->num_subbuf;
+ crash_abi->mode = (uint32_t) chanb->config.mode;
+
+ if (config->cb.content_size_field) {
+ size_t offset, length;
+
+ config->cb.content_size_field(config, &offset, &length);
+ crash_abi->offset.content_size = offset;
+ crash_abi->length.content_size = length;
+ } else {
+ crash_abi->offset.content_size = 0;
+ crash_abi->length.content_size = 0;
+ }
+ if (config->cb.packet_size_field) {
+ size_t offset, length;
+
+ config->cb.packet_size_field(config, &offset, &length);
+ crash_abi->offset.packet_size = offset;
+ crash_abi->length.packet_size = length;
+ } else {
+ crash_abi->offset.packet_size = 0;
+ crash_abi->length.packet_size = 0;
+ }
+}
+
/*
* Must be called under cpu hotplug protection.
*/
if (buf->backend.allocated)
return 0;
- ret = lib_ring_buffer_backend_create(&buf->backend, &chan->backend,
- cpu, handle, shmobj);
- if (ret)
- return ret;
-
align_shm(shmobj, __alignof__(struct commit_counters_hot));
set_shmp(buf->commit_hot,
zalloc_shm(shmobj,
sizeof(struct commit_counters_hot) * chan->backend.num_subbuf));
if (!shmp(handle, buf->commit_hot)) {
- ret = -ENOMEM;
- goto free_chanbuf;
+ return -ENOMEM;
}
align_shm(shmobj, __alignof__(struct commit_counters_cold));
goto free_commit;
}
+ ret = lib_ring_buffer_backend_create(&buf->backend, &chan->backend,
+ cpu, handle, shmobj);
+ if (ret) {
+ goto free_init;
+ }
+
/*
* Write the subbuffer header for first subbuffer so we know the total
* duration of data gathering.
tsc = config->cb.ring_buffer_clock_read(shmp(handle, buf->backend.chan));
config->cb.buffer_begin(buf, tsc, 0, handle);
v_add(config, subbuf_header_size, &shmp_index(handle, buf->commit_hot, 0)->cc);
+ v_add(config, subbuf_header_size, &shmp_index(handle, buf->commit_hot, 0)->seq);
if (config->cb.buffer_create) {
ret = config->cb.buffer_create(buf, priv, cpu, chanb->name, handle);
if (ret)
- goto free_init;
+ goto free_chanbuf;
}
+
+ init_crash_abi(config, &buf->crash_abi, buf, chanb, shmobj, handle);
+
buf->backend.allocated = 1;
return 0;
for_each_possible_cpu(cpu) {
struct lttng_ust_lib_ring_buffer *buf =
shmp(handle, chan->backend.buf[cpu].shmp);
+
+ if (!buf)
+ abort();
if (uatomic_read(&buf->active_readers))
lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE,
chan->handle);
struct lttng_ust_lib_ring_buffer *buf =
shmp(handle, chan->backend.buf[0].shmp);
+ if (!buf)
+ abort();
if (uatomic_read(&buf->active_readers))
lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE,
chan->handle);
return;
}
+static
+int lib_ring_buffer_poll_deliver(const struct lttng_ust_lib_ring_buffer_config *config,
+ struct lttng_ust_lib_ring_buffer *buf,
+ struct channel *chan,
+ struct lttng_ust_shm_handle *handle)
+{
+ unsigned long consumed_old, consumed_idx, commit_count, write_offset;
+
+ consumed_old = uatomic_read(&buf->consumed);
+ consumed_idx = subbuf_index(consumed_old, chan);
+ commit_count = v_read(config, &shmp_index(handle, buf->commit_cold, consumed_idx)->cc_sb);
+ /*
+ * No memory barrier here, since we are only interested
+ * in a statistically correct polling result. The next poll will
+ * get the data is we are racing. The mb() that ensures correct
+ * memory order is in get_subbuf.
+ */
+ write_offset = v_read(config, &buf->offset);
+
+ /*
+ * Check that the subbuffer we are trying to consume has been
+ * already fully committed.
+ */
+
+ if (((commit_count - chan->backend.subbuf_size)
+ & chan->commit_count_mask)
+ - (buf_trunc(consumed_old, chan)
+ >> chan->backend.num_subbuf_order)
+ != 0)
+ return 0;
+
+ /*
+ * Check that we are not about to read the same subbuffer in
+ * which the writer head is.
+ */
+ if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed_old, chan)
+ == 0)
+ return 0;
+
+ return 1;
+}
+
+static
+void lib_ring_buffer_wakeup(struct lttng_ust_lib_ring_buffer *buf,
+ struct lttng_ust_shm_handle *handle)
+{
+ int wakeup_fd = shm_get_wakeup_fd(handle, &buf->self._ref);
+ sigset_t sigpipe_set, pending_set, old_set;
+ int ret, sigpipe_was_pending = 0;
+
+ if (wakeup_fd < 0)
+ return;
+
+ /*
+ * Wake-up the other end by writing a null byte in the pipe
+ * (non-blocking). Important note: Because writing into the
+ * pipe is non-blocking (and therefore we allow dropping wakeup
+ * data, as long as there is wakeup data present in the pipe
+ * buffer to wake up the consumer), the consumer should perform
+ * the following sequence for waiting:
+ * 1) empty the pipe (reads).
+ * 2) check if there is data in the buffer.
+ * 3) wait on the pipe (poll).
+ *
+ * Discard the SIGPIPE from write(), not disturbing any SIGPIPE
+ * that might be already pending. If a bogus SIGPIPE is sent to
+ * the entire process concurrently by a malicious user, it may
+ * be simply discarded.
+ */
+ ret = sigemptyset(&pending_set);
+ assert(!ret);
+ /*
+ * sigpending returns the mask of signals that are _both_
+ * blocked for the thread _and_ pending for either the thread or
+ * the entire process.
+ */
+ ret = sigpending(&pending_set);
+ assert(!ret);
+ sigpipe_was_pending = sigismember(&pending_set, SIGPIPE);
+ /*
+ * If sigpipe was pending, it means it was already blocked, so
+ * no need to block it.
+ */
+ if (!sigpipe_was_pending) {
+ ret = sigemptyset(&sigpipe_set);
+ assert(!ret);
+ ret = sigaddset(&sigpipe_set, SIGPIPE);
+ assert(!ret);
+ ret = pthread_sigmask(SIG_BLOCK, &sigpipe_set, &old_set);
+ assert(!ret);
+ }
+ do {
+ ret = write(wakeup_fd, "", 1);
+ } while (ret == -1L && errno == EINTR);
+ if (ret == -1L && errno == EPIPE && !sigpipe_was_pending) {
+ struct timespec timeout = { 0, 0 };
+ do {
+ ret = sigtimedwait(&sigpipe_set, NULL,
+ &timeout);
+ } while (ret == -1L && errno == EINTR);
+ }
+ if (!sigpipe_was_pending) {
+ ret = pthread_sigmask(SIG_SETMASK, &old_set, NULL);
+ assert(!ret);
+ }
+}
+
static
void lib_ring_buffer_channel_do_read(struct channel *chan)
{
struct lttng_ust_lib_ring_buffer *buf =
shmp(handle, chan->backend.buf[cpu].shmp);
+ if (!buf)
+ abort();
if (uatomic_read(&buf->active_readers)
&& lib_ring_buffer_poll_deliver(config, buf,
chan, handle)) {
struct lttng_ust_lib_ring_buffer *buf =
shmp(handle, chan->backend.buf[0].shmp);
+ if (!buf)
+ abort();
if (uatomic_read(&buf->active_readers)
&& lib_ring_buffer_poll_deliver(config, buf,
chan, handle)) {
}
its.it_value.tv_sec = chan->switch_timer_interval / 1000000;
- its.it_value.tv_nsec = chan->switch_timer_interval % 1000000;
+ its.it_value.tv_nsec = (chan->switch_timer_interval % 1000000) * 1000;
its.it_interval.tv_sec = its.it_value.tv_sec;
its.it_interval.tv_nsec = its.it_value.tv_nsec;
}
its.it_value.tv_sec = chan->read_timer_interval / 1000000;
- its.it_value.tv_nsec = chan->read_timer_interval % 1000000;
+ its.it_value.tv_nsec = (chan->read_timer_interval % 1000000) * 1000;
its.it_interval.tv_sec = its.it_value.tv_sec;
its.it_interval.tv_nsec = its.it_value.tv_nsec;
* padding to let readers get those sub-buffers.
* Used for live streaming.
* @read_timer_interval: Time interval (in us) to wake up pending readers.
+ * @stream_fds: array of stream file descriptors.
+ * @nr_stream_fds: number of file descriptors in array.
*
* Holds cpu hotplug.
* Returns NULL on failure.
void *priv_data_init,
void *buf_addr, size_t subbuf_size,
size_t num_subbuf, unsigned int switch_timer_interval,
- unsigned int read_timer_interval)
+ unsigned int read_timer_interval,
+ const int *stream_fds, int nr_stream_fds)
{
int ret;
size_t shmsize, chansize;
else
nr_streams = 1;
+ if (nr_stream_fds != nr_streams)
+ return NULL;
+
if (lib_ring_buffer_check_config(config, switch_timer_interval,
read_timer_interval))
return NULL;
shmsize += priv_data_size;
/* Allocate normal memory for channel (not shared) */
- shmobj = shm_object_table_alloc(handle->table, shmsize, SHM_OBJECT_MEM);
+ shmobj = shm_object_table_alloc(handle->table, shmsize, SHM_OBJECT_MEM,
+ -1);
if (!shmobj)
goto error_append;
/* struct channel is at object 0, offset 0 (hardcoded) */
}
ret = channel_backend_init(&chan->backend, name, config,
- subbuf_size, num_subbuf, handle);
+ subbuf_size, num_subbuf, handle,
+ stream_fds);
if (ret)
goto error_backend_init;
struct channel *chan = shmp(handle, buf->backend.chan);
const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
unsigned long consumed_cur, consumed_idx, commit_count, write_offset;
- int ret;
- int finalized;
+ int ret, finalized, nr_retry = LTTNG_UST_RING_BUFFER_GET_RETRY;
retry:
finalized = CMM_ACCESS_ONCE(buf->finalized);
/*
* Check that the subbuffer we are trying to consume has been
- * already fully committed.
+ * already fully committed. There are a few causes that can make
+ * this unavailability situation occur:
+ *
+ * Temporary (short-term) situation:
+ * - Application is running on a different CPU, between reserve
+ * and commit ring buffer operations,
+ * - Application is preempted between reserve and commit ring
+ * buffer operations,
+ *
+ * Long-term situation:
+ * - Application is stopped (SIGSTOP) between reserve and commit
+ * ring buffer operations. Could eventually be resumed by
+ * SIGCONT.
+ * - Application is killed (SIGTERM, SIGINT, SIGKILL) between
+ * reserve and commit ring buffer operation.
+ *
+ * From a consumer perspective, handling short-term
+ * unavailability situations is performed by retrying a few
+ * times after a delay. Handling long-term unavailability
+ * situations is handled by failing to get the sub-buffer.
+ *
+ * In all of those situations, if the application is taking a
+ * long time to perform its commit after ring buffer space
+ * reservation, we can end up in a situation where the producer
+ * will fill the ring buffer and try to write into the same
+ * sub-buffer again (which has a missing commit). This is
+ * handled by the producer in the sub-buffer switch handling
+ * code of the reserve routine by detecting unbalanced
+ * reserve/commit counters and discarding all further events
+ * until the situation is resolved in those situations. Two
+ * scenarios can occur:
+ *
+ * 1) The application causing the reserve/commit counters to be
+ * unbalanced has been terminated. In this situation, all
+ * further events will be discarded in the buffers, and no
+ * further buffer data will be readable by the consumer
+ * daemon. Tearing down the UST tracing session and starting
+ * anew is a work-around for those situations. Note that this
+ * only affects per-UID tracing. In per-PID tracing, the
+ * application vanishes with the termination, and therefore
+ * no more data needs to be written to the buffers.
+ * 2) The application causing the unbalance has been delayed for
+ * a long time, but will eventually try to increment the
+ * commit counter after eventually writing to the sub-buffer.
+ * This situation can cause events to be discarded until the
+ * application resumes its operations.
*/
if (((commit_count - chan->backend.subbuf_size)
& chan->commit_count_mask)
- (buf_trunc(consumed, chan)
>> chan->backend.num_subbuf_order)
- != 0)
- goto nodata;
+ != 0) {
+ if (nr_retry-- > 0) {
+ if (nr_retry <= (LTTNG_UST_RING_BUFFER_GET_RETRY >> 1))
+ (void) poll(NULL, 0, LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS);
+ goto retry;
+ } else {
+ goto nodata;
+ }
+ }
/*
* Check that we are not about to read the same subbuffer in
* 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.
+ *
+ * The short-lived race window described here can be affected by
+ * application signals and preemption, thus requiring to bound
+ * the loop to a maximum number of retry.
*/
ret = update_read_sb_index(config, &buf->backend, &chan->backend,
consumed_idx, buf_trunc_val(consumed, chan),
handle);
- if (ret)
- goto retry;
+ if (ret) {
+ if (nr_retry-- > 0) {
+ if (nr_retry <= (LTTNG_UST_RING_BUFFER_GET_RETRY >> 1))
+ (void) poll(NULL, 0, LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS);
+ goto retry;
+ } else {
+ goto nodata;
+ }
+ }
subbuffer_id_clear_noref(config, &buf->backend.buf_rsb.id);
buf->get_subbuf_consumed = consumed;
/*
* lib_ring_buffer_switch_old_start: Populate old subbuffer header.
*
- * Only executed when the buffer is finalized, in SWITCH_FLUSH.
+ * Only executed by SWITCH_FLUSH, which can be issued while tracing is
+ * active or at buffer finalization (destroy).
*/
static
void lib_ring_buffer_switch_old_start(struct lttng_ust_lib_ring_buffer *buf,
unsigned long sb_index, commit_count;
/*
- * We are performing a SWITCH_FLUSH. At this stage, there are no
- * concurrent writes into the buffer.
+ * We are performing a SWITCH_FLUSH. There may be concurrent
+ * writes into the buffer if e.g. invoked while performing a
+ * snapshot on an active trace.
*
- * 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 the client does not save any header information
+ * (sub-buffer header size == 0), 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;
return 0;
}
+static
+void lib_ring_buffer_vmcore_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config,
+ struct lttng_ust_lib_ring_buffer *buf,
+ unsigned long commit_count,
+ unsigned long idx,
+ struct lttng_ust_shm_handle *handle)
+{
+ if (config->oops == RING_BUFFER_OOPS_CONSISTENCY)
+ v_set(config, &shmp_index(handle, buf->commit_hot, idx)->seq, commit_count);
+}
+
+void lib_ring_buffer_check_deliver_slow(const struct lttng_ust_lib_ring_buffer_config *config,
+ struct lttng_ust_lib_ring_buffer *buf,
+ struct channel *chan,
+ unsigned long offset,
+ unsigned long commit_count,
+ unsigned long idx,
+ struct lttng_ust_shm_handle *handle,
+ uint64_t tsc)
+{
+ unsigned long old_commit_count = commit_count
+ - chan->backend.subbuf_size;
+
+ /*
+ * If we succeeded at updating cc_sb below, we are the subbuffer
+ * writer delivering the subbuffer. Deals with concurrent
+ * updates of the "cc" value without adding a add_return atomic
+ * operation to the fast path.
+ *
+ * We are doing the delivery in two steps:
+ * - First, we cmpxchg() cc_sb to the new value
+ * old_commit_count + 1. This ensures that we are the only
+ * subbuffer user successfully filling the subbuffer, but we
+ * do _not_ set the cc_sb value to "commit_count" yet.
+ * Therefore, other writers that would wrap around the ring
+ * buffer and try to start writing to our subbuffer would
+ * have to drop records, because it would appear as
+ * non-filled.
+ * We therefore have exclusive access to the subbuffer control
+ * structures. This mutual exclusion with other writers is
+ * crucially important to perform record overruns count in
+ * flight recorder mode locklessly.
+ * - When we are ready to release the subbuffer (either for
+ * reading or for overrun by other writers), we simply set the
+ * cc_sb value to "commit_count" and perform delivery.
+ *
+ * The subbuffer size is least 2 bytes (minimum size: 1 page).
+ * This guarantees that old_commit_count + 1 != commit_count.
+ */
+
+ /*
+ * Order prior updates to reserve count prior to the
+ * commit_cold cc_sb update.
+ */
+ cmm_smp_wmb();
+ if (caa_likely(v_cmpxchg(config, &shmp_index(handle, buf->commit_cold, idx)->cc_sb,
+ old_commit_count, old_commit_count + 1)
+ == old_commit_count)) {
+ /*
+ * Start of exclusive subbuffer access. We are
+ * guaranteed to be the last writer in this subbuffer
+ * and any other writer trying to access this subbuffer
+ * in this state is required to drop records.
+ */
+ v_add(config,
+ subbuffer_get_records_count(config,
+ &buf->backend,
+ idx, handle),
+ &buf->records_count);
+ v_add(config,
+ subbuffer_count_records_overrun(config,
+ &buf->backend,
+ idx, handle),
+ &buf->records_overrun);
+ config->cb.buffer_end(buf, tsc, idx,
+ lib_ring_buffer_get_data_size(config,
+ buf,
+ idx,
+ handle),
+ handle);
+
+ /*
+ * Increment the packet counter while we have exclusive
+ * access.
+ */
+ subbuffer_inc_packet_count(config, &buf->backend, idx, handle);
+
+ /*
+ * Set noref flag and offset for this subbuffer id.
+ * Contains a memory barrier that ensures counter stores
+ * are ordered before set noref and offset.
+ */
+ lib_ring_buffer_set_noref_offset(config, &buf->backend, idx,
+ buf_trunc_val(offset, chan), handle);
+
+ /*
+ * Order set_noref and record counter updates before the
+ * end of subbuffer exclusive access. Orders with
+ * respect to writers coming into the subbuffer after
+ * wrap around, and also order wrt concurrent readers.
+ */
+ cmm_smp_mb();
+ /* End of exclusive subbuffer access */
+ v_set(config, &shmp_index(handle, buf->commit_cold, idx)->cc_sb,
+ commit_count);
+ /*
+ * Order later updates to reserve count after
+ * the commit cold cc_sb update.
+ */
+ cmm_smp_wmb();
+ lib_ring_buffer_vmcore_check_deliver(config, buf,
+ commit_count, idx, handle);
+
+ /*
+ * RING_BUFFER_WAKEUP_BY_WRITER wakeup is not lock-free.
+ */
+ if (config->wakeup == RING_BUFFER_WAKEUP_BY_WRITER
+ && uatomic_read(&buf->active_readers)
+ && lib_ring_buffer_poll_deliver(config, buf, chan, handle)) {
+ lib_ring_buffer_wakeup(buf, handle);
+ }
+ }
+}
+
/*
* Force a read (imply TLS fixup for dlopen) of TLS variables.
*/
projects / lttng-ust.git / blobdiff