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authorWaiman Long <longman@redhat.com>2019-01-09 23:03:25 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-03-27 14:14:43 +0900
commit0e0f7b30721233ce610bde2395a8e58ff7771475 (patch)
treea595f1773951965bddc73e8325b733feb1cde0a7 /kernel/locking
parent206a76a684a7c98813fcd5146902f0c2cd29f70b (diff)
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locking/lockdep: Add debug_locks check in __lock_downgrade()
commit 71492580571467fb7177aade19c18ce7486267f5 upstream. Tetsuo Handa had reported he saw an incorrect "downgrading a read lock" warning right after a previous lockdep warning. It is likely that the previous warning turned off lock debugging causing the lockdep to have inconsistency states leading to the lock downgrade warning. Fix that by add a check for debug_locks at the beginning of __lock_downgrade(). Debugged-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Reported-by: syzbot+53383ae265fb161ef488@syzkaller.appspotmail.com Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Link: https://lkml.kernel.org/r/1547093005-26085-1-git-send-email-longman@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/locking')
-rw-r--r--kernel/locking/lockdep.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 26b57e24476f..0cbdbbb0729f 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3567,6 +3567,9 @@ __lock_set_class(struct lockdep_map *lock, const char *name,
unsigned int depth;
int i;
+ if (unlikely(!debug_locks))
+ return 0;
+
depth = curr->lockdep_depth;
/*
* This function is about (re)setting the class of a held lock,