From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Sat, 9 Mar 2013 16:56:25 +0000 (-0500)
Subject: Add mutex for channel wakeup fd update
X-Git-Tag: v2.2.0-rc1~53
X-Git-Url: http://git.liburcu.org/?p=lttng-ust.git;a=commitdiff_plain;h=cb7378b3cf177d007917a82a5fe2514e2015bb26

Add mutex for channel wakeup fd update

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/liblttng-ust-ctl/ustctl.c b/liblttng-ust-ctl/ustctl.c
index e00caf15..18bf614b 100644
--- a/liblttng-ust-ctl/ustctl.c
+++ b/liblttng-ust-ctl/ustctl.c
@@ -953,6 +953,8 @@ struct ustctl_consumer_channel *
 	}
 	chan->chan->ops = &transport->ops;
 	memcpy(&chan->attr, attr, sizeof(chan->attr));
+	chan->wait_fd = ustctl_channel_get_wait_fd(chan);
+	chan->wakeup_fd = ustctl_channel_get_wakeup_fd(chan);
 	return chan;
 
 chan_error:
@@ -1042,19 +1044,27 @@ end:
 int ustctl_channel_close_wait_fd(struct ustctl_consumer_channel *consumer_chan)
 {
 	struct channel *chan;
+	int ret;
 
 	chan = consumer_chan->chan->chan;
-	return ring_buffer_channel_close_wait_fd(&chan->backend.config,
+	ret = ring_buffer_channel_close_wait_fd(&chan->backend.config,
 			chan, chan->handle);
+	if (!ret)
+		consumer_chan->wait_fd = -1;
+	return ret;
 }
 
 int ustctl_channel_close_wakeup_fd(struct ustctl_consumer_channel *consumer_chan)
 {
 	struct channel *chan;
+	int ret;
 
 	chan = consumer_chan->chan->chan;
-	return ring_buffer_channel_close_wakeup_fd(&chan->backend.config,
+	ret = ring_buffer_channel_close_wakeup_fd(&chan->backend.config,
 			chan, chan->handle);
+	if (!ret)
+		consumer_chan->wakeup_fd = -1;
+	return ret;
 }
 
 int ustctl_stream_close_wait_fd(struct ustctl_consumer_stream *stream)
diff --git a/libringbuffer/ring_buffer_frontend.c b/libringbuffer/ring_buffer_frontend.c
index 5d1bc4ad..871d96d1 100644
--- 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,