linux-kernel - [tip:perf/urgent] lockdep, kmemcheck: Annotate ->lock in lockdep_init

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Message-ID: <tip-a33caeb118198286309859f014c0662f3ed54ed4@git.kernel.org>
Date:	Tue, 6 Dec 2011 12:14:58 -0800
From:	tip-bot for Yong Zhang <yong.zhang0@...il.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, vegard.nossum@...il.com,
	sergey.senozhatsky@...il.com, bp@...en8.de, stable@...nel.org,
	tj@...nel.org, tglx@...utronix.de, yong.zhang0@...il.com,
	rientjes@...gle.com, mingo@...e.hu
Subject: [tip:perf/urgent] lockdep, kmemcheck: Annotate ->lock in lockdep_init_map()

Commit-ID:  a33caeb118198286309859f014c0662f3ed54ed4
Gitweb:     http://git.kernel.org/tip/a33caeb118198286309859f014c0662f3ed54ed4
Author:     Yong Zhang <yong.zhang0@...il.com>
AuthorDate: Wed, 9 Nov 2011 16:04:51 +0800
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 6 Dec 2011 18:18:13 +0100

lockdep, kmemcheck: Annotate ->lock in lockdep_init_map()

Since commit f59de89 ("lockdep: Clear whole lockdep_map on initialization"),
lockdep_init_map() will clear all the struct. But it will break
lock_set_class()/lock_set_subclass(). A typical race condition
is like below:

     CPU A                                   CPU B
lock_set_subclass(lockA);
 lock_set_class(lockA);
   lockdep_init_map(lockA);
     /* lockA->name is cleared */
     memset(lockA);
                                     __lock_acquire(lockA);
                                       /* lockA->class_cache[] is cleared */
                                       register_lock_class(lockA);
                                         look_up_lock_class(lockA);
                                           WARN_ON_ONCE(class->name !=
                                                     lock->name);

     lock->name = name;

So restore to what we have done before commit f59de89 but annotate
->lock with kmemcheck_mark_initialized() to suppress the kmemcheck
warning reported in commit f59de89.

Reported-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Reported-by: Borislav Petkov <bp@...en8.de>
Suggested-by: Vegard Nossum <vegard.nossum@...il.com>
Signed-off-by: Yong Zhang <yong.zhang0@...il.com>
Cc: Tejun Heo <tj@...nel.org>
Cc: David Rientjes <rientjes@...gle.com>
Cc: <stable@...nel.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/20111109080451.GB8124@zhy
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/lockdep.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index e69434b..b2e08c9 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -44,6 +44,7 @@
 #include <linux/stringify.h>
 #include <linux/bitops.h>
 #include <linux/gfp.h>
+#include <linux/kmemcheck.h>
 
 #include <asm/sections.h>
 
@@ -2948,7 +2949,12 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
 void lockdep_init_map(struct lockdep_map *lock, const char *name,
 		      struct lock_class_key *key, int subclass)
 {
-	memset(lock, 0, sizeof(*lock));
+	int i;
+
+	kmemcheck_mark_initialized(lock, sizeof(*lock));
+
+	for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
+		lock->class_cache[i] = NULL;
 
 #ifdef CONFIG_LOCK_STAT
 	lock->cpu = raw_smp_processor_id();
--
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