linux-kernel - [PATCH] Relay : fix cpu offline problem

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Date:	Tue, 9 Dec 2008 11:25:12 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Tom Zanussi <zanussi@...cast.net>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] 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 <mathieu.desnoyers@...ymtl.ca>
CC: Lai Jiangshan <laijs@...fujitsu.com>
CC: Tom Zanussi <zanussi@...cast.net>
---
 kernel/relay.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

Index: linux-2.6-lttng/kernel/relay.c
===================================================================
--- linux-2.6-lttng.orig/kernel/relay.c	2008-12-09 10:58:45.000000000 -0500
+++ linux-2.6-lttng/kernel/relay.c	2008-12-09 11:09:58.000000000 -0500
@@ -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);
-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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