Implement LTTNG_UST_BLOCKING_RETRY_TIMEOUT

[lttng-ust.git] / libringbuffer / ring_buffer_frontend.c

diff --git a/libringbuffer/ring_buffer_frontend.c b/libringbuffer/ring_buffer_frontend.c
index be20d69b9864d014c9271807254aef282c8b59c8..768e2a12a3d62c2d069b212beeac8b7e7a839b24 100644 (file)
--- a/libringbuffer/ring_buffer_frontend.c
+++ b/libringbuffer/ring_buffer_frontend.c
@@ -72,7 +72,7 @@
 #include "backend.h"
 #include "frontend.h"
 #include "shm.h"
-#include "tlsfixup.h"
+#include "rb-init.h"
 #include "../liblttng-ust/compat.h"    /* For ENODATA */
 
 /* Print DBG() messages about events lost only every 1048576 hits */
@@ -84,6 +84,7 @@
 #define CLOCKID                CLOCK_MONOTONIC
 #define LTTNG_UST_RING_BUFFER_GET_RETRY                10
 #define LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS   10
+#define RETRY_DELAY_MS                         100     /* 100 ms. */
 
 /*
  * Non-static to ensure the compiler does not optimize away the xor.
@@ -149,6 +150,14 @@ static struct timer_signal_data timer_signal = {
        .lock = PTHREAD_MUTEX_INITIALIZER,
 };
 
+int lttng_ust_blocking_retry_timeout =
+               CONFIG_LTTNG_UST_DEFAULT_BLOCKING_RETRY_TIMEOUT_MS;
+
+void lttng_ust_ringbuffer_set_retry_timeout(int timeout)
+{
+       lttng_ust_blocking_retry_timeout = timeout;
+}
+
 /**
  * lib_ring_buffer_reset - Reset ring buffer to initial values.
  * @buf: Ring buffer.
@@ -1985,6 +1994,23 @@ void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf, enum swi
        lib_ring_buffer_switch_old_end(buf, chan, &offsets, tsc, handle);
 }
 
+static
+bool handle_blocking_retry(int *timeout_left_ms)
+{
+       int timeout = *timeout_left_ms, delay;
+
+       if (caa_likely(!timeout))
+               return false;   /* Do not retry, discard event. */
+       if (timeout < 0)        /* Wait forever. */
+               delay = RETRY_DELAY_MS;
+       else
+               delay = min_t(int, timeout, RETRY_DELAY_MS);
+       (void) poll(NULL, 0, delay);
+       if (timeout > 0)
+               *timeout_left_ms -= delay;
+       return true;    /* Retry. */
+}
+
 /*
  * Returns :
  * 0 if ok
@@ -2001,6 +2027,7 @@ int lib_ring_buffer_try_reserve_slow(struct lttng_ust_lib_ring_buffer *buf,
        const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
        struct lttng_ust_shm_handle *handle = ctx->handle;
        unsigned long reserve_commit_diff, offset_cmp;
+       int timeout_left_ms = lttng_ust_blocking_retry_timeout;
 
 retry:
        offsets->begin = offset_cmp = v_read(config, &buf->offset);
@@ -2083,6 +2110,9 @@ retry:
                                >= chan->backend.buf_size)) {
                                unsigned long nr_lost;
 
+                               if (handle_blocking_retry(&timeout_left_ms))
+                                       goto retry;
+
                                /*
                                 * We do not overwrite non consumed buffers
                                 * and we are full : record is lost.