Relay : fix cpu offline problem

Here is a fix for how relay handles cpu hotplug in the allocation error path. If a cpu goes down while allocating, it may result in a buffer never being freed.

Lai Jiangshan originally identified this problem in the LTTng fork of relay (ltt-relay-alloc). Here is the fix which applies to the original kernel/relay.c.

Signed-off-by Mathieu Desnoyers <[email protected]>

CC Lai Jiangshan <[email protected]>

CC Tom Zanussi <[email protected]>

---
 kernel/relay.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

Index: linux-2.6-lttng/kernel/relay.c
===================================================================

kernel/relay.c +3 -4

@@ -611,10 +611,9 @@ struct rchan *relay_open(const char *bas
 	return chan;
 
 free_bufs:
-	for_each_online_cpu(i) {
-		if (!chan->buf[i])
-			break;
-		relay_close_buf(chan->buf[i]);
+	for_each_possible_cpu(i) {
+		if (chan->buf[i])
+			relay_close_buf(chan->buf[i]);
 	}
 
 	kref_put(&chan->kref, relay_destroy_channel);

Hi, Mathieu Desnoyers

I have fixed this problem in mainline.
http://lkml.org/lkml/2008/11/14/74

Lai

Quoted 32 lines · Mathieu Desnoyers

Here is a fix for how relay handles cpu hotplug in the allocation error path. If a cpu goes down while allocating, it may result in a buffer never being freed.

Lai Jiangshan originally identified this problem in the LTTng fork of relay (ltt-relay-alloc). Here is the fix which applies to the original kernel/relay.c.

Signed-off-by Mathieu Desnoyers <[email protected]>

CC Lai Jiangshan <[email protected]>

CC Tom Zanussi <[email protected]>

---
 kernel/relay.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

Index: linux-2.6-lttng/kernel/relay.c
===================================================================

kernel/relay.c +3 -4

@@ -611,10 +611,9 @@ struct rchan *relay_open(const char *bas
 	return chan;
 
 free_bufs:
-	for_each_online_cpu(i) {
-		if (!chan->buf[i])
-			break;
-		relay_close_buf(chan->buf[i]);
+	for_each_possible_cpu(i) {
+		if (chan->buf[i])
+			relay_close_buf(chan->buf[i]);
 	}
 
 	kref_put(&chan->kref, relay_destroy_channel);