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Subject[tip:core/locking] lockdep, kmemcheck: Annotate ->lock in lockdep_init_map()
Commit-ID:  d3d03d4fc5b1bec3a579112de170a9676e9d97cb
Gitweb: http://git.kernel.org/tip/d3d03d4fc5b1bec3a579112de170a9676e9d97cb
Author: Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Wed, 9 Nov 2011 16:04:51 +0800
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 6 Dec 2011 08:16:51 +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@gmail.com>
Reported-by: Borislav Petkov <bp@alien8.de>
Suggested-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111109080451.GB8124@zhy
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/lockdep.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index a2ab30c..54cc0dc 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>

@@ -2950,7 +2951,12 @@ 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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