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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@polymtl.ca>
CC: Lai Jiangshan <laijs@cn.fujitsu.com>
CC: Tom Zanussi <zanussi@comcast.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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