lockdep, kmemcheck: Annotate ->lock in lockdep_init_map()
Yong Zhang [Wed, 9 Nov 2011 08:04:51 +0000 (16:04 +0800)]
commit a33caeb118198286309859f014c0662f3ed54ed4 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

kernel/lockdep.c

index 91d67ce..4479606 100644 (file)
@@ -44,6 +44,7 @@
 #include <linux/stringify.h>
 #include <linux/bitops.h>
 #include <linux/gfp.h>
+#include <linux/kmemcheck.h>
 
 #include <asm/sections.h>
 
@@ -2874,7 +2875,12 @@ 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();