lkml.org 
[lkml]   [2019]   [Mar]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH AUTOSEL 4.4 46/63] locking/lockdep: Add debug_locks check in __lock_downgrade()
    Date
    From: Waiman Long <longman@redhat.com>

    [ Upstream commit 71492580571467fb7177aade19c18ce7486267f5 ]

    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: Sasha Levin <sashal@kernel.org>
    ---
    kernel/locking/lockdep.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
    index 774ab79d3ec7..a49c565529a0 100644
    --- a/kernel/locking/lockdep.c
    +++ b/kernel/locking/lockdep.c
    @@ -3314,6 +3314,9 @@ __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,
    --
    2.19.1
    \
     
     \ /
      Last update: 2019-03-27 19:25    [W:4.453 / U:1.036 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site