Add mutex for channel wakeup fd update

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

diff --git a/libringbuffer/ring_buffer_frontend.c b/libringbuffer/ring_buffer_frontend.c
index 5d1bc4adbcdf37007269b8b6e3f49db0b1c9688f..871d96d1c6e07848348cadbeb872d5a480214add 100644 (file)
--- a/libringbuffer/ring_buffer_frontend.c
+++ b/libringbuffer/ring_buffer_frontend.c
@@ -112,6 +112,12 @@ struct switch_offsets {
 
 DEFINE_URCU_TLS(unsigned int, lib_ring_buffer_nesting);
 
+/*
+ * wakeup_fd_mutex protects wakeup fd use by timer from concurrent
+ * close.
+ */
+static pthread_mutex_t wakeup_fd_mutex = PTHREAD_MUTEX_INITIALIZER;
+
 static
 void lib_ring_buffer_print_errors(struct channel *chan,
                                struct lttng_ust_lib_ring_buffer *buf, int cpu,
@@ -301,6 +307,7 @@ void lib_ring_buffer_channel_switch_timer(int sig, siginfo_t *si, void *uc)
 
        DBG("Timer for channel %p\n", chan);
 
+       pthread_mutex_lock(&wakeup_fd_mutex);
        if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
                for_each_possible_cpu(cpu) {
                        struct lttng_ust_lib_ring_buffer *buf =
@@ -316,6 +323,7 @@ void lib_ring_buffer_channel_switch_timer(int sig, siginfo_t *si, void *uc)
                        lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE,
                                chan->handle);
        }
+       pthread_mutex_unlock(&wakeup_fd_mutex);
        return;
 }
 
@@ -912,6 +920,7 @@ int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_co
                        int cpu)
 {
        struct shm_ref *ref;
+       int ret;
 
        if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
                cpu = 0;
@@ -920,7 +929,10 @@ int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_co
                        return -EINVAL;
        }
        ref = &chan->backend.buf[cpu].shmp._ref;
-       return shm_close_wakeup_fd(handle, ref);
+       pthread_mutex_lock(&wakeup_fd_mutex);
+       ret = shm_close_wakeup_fd(handle, ref);
+       pthread_mutex_unlock(&wakeup_fd_mutex);
+       return ret;
 }
 
 int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,