On 9/25/19 6:01 AM, Baolin Wang wrote: > From: Waiman Long <[email protected]> > > [Upstream commit 513e1073d52e55b8024b4f238a48de7587c64ccf] > > 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(). > > Reported-by: Tetsuo Handa <[email protected]> > Reported-by: [email protected] > Signed-off-by: Waiman Long <[email protected]> > Signed-off-by: Peter Zijlstra (Intel) <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: Linus Torvalds <[email protected]> > Cc: Paul E. McKenney <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Will Deacon <[email protected]> > Link: > https://lkml.kernel.org/r/[email protected] > Signed-off-by: Ingo Molnar <[email protected]> > Signed-off-by: Baolin Wang <[email protected]> > --- > kernel/locking/lockdep.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index 565005a..5c370c6 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -3650,6 +3650,9 @@ static int reacquire_held_locks(struct task_struct > *curr, unsigned int depth, > 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,
Apparently, there are 2 such patches in the upstream kernel - commit 513e1073d52e55b8024b4f238a48de7587c64ccf and 71492580571467fb7177aade19c18ce7486267f5. These are probably caused by the fact that there are 2 places in the code that can match the hunks. Anyway, this looks like it is applying to the wrong function. It should be applied to __lock_downgrade. Though it shouldn't harm if it is applied to the wrong function. Cheers, Longman
