From: Gautham R Shenoy <ego@in.ibm.com>
Date: Mon, 6 Nov 2006 07:52:04 +0000 (-0800)
Subject: [PATCH] Fix the spurious unlock_cpu_hotplug false warnings
X-Git-Tag: v2.6.19-rc5~18
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4b96b1a10cb00c867103b21f0f2a6c91b705db11;p=linux-2.6

[PATCH] Fix the spurious unlock_cpu_hotplug false warnings

Cpu-hotplug locking has a minor race case caused because of setting the
variable "recursive" to NULL *after* releasing the cpu_bitmask_lock in the
function unlock_cpu_hotplug,instead of doing so before releasing the
cpu_bitmask_lock.

This was the cause of most of the recent false spurious lock_cpu_unlock
warnings.

This should fix the problem reported by Martin Lorenz reported in
http://lkml.org/lkml/2006/10/29/127.

Thanks to Srinivasa DS for pointing it out.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 663c920b22..272254f20d 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -58,8 +58,8 @@ void unlock_cpu_hotplug(void)
 		recursive_depth--;
 		return;
 	}
-	mutex_unlock(&cpu_bitmask_lock);
 	recursive = NULL;
+	mutex_unlock(&cpu_bitmask_lock);
 }
 EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);