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Date: Mon, 30 Sep 2019 10:46:39 +0900
From: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To: Sasha Levin <sashal@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-kernel@...r.kernel.org, stable@...r.kernel.org,
syzbot+53383ae265fb161ef488@...kaller.appspotmail.com,
Waiman Long <longman@...hat.com>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Thomas Gleixner <tglx@...utronix.de>,
Will Deacon <will.deacon@....com>,
Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 4.19 36/63] locking/lockdep: Add debug_locks check in
__lock_downgrade()
On 2019/09/30 9:28, Sasha Levin wrote:
> On Sun, Sep 29, 2019 at 11:43:38PM +0900, Tetsuo Handa wrote:
>> On 2019/09/29 22:54, Greg Kroah-Hartman wrote:
>>> From: Waiman Long <longman@...hat.com>
>>>
>>> [ 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().
>>
>> Please drop "[PATCH 4.19 36/63] locking/lockdep: Add debug_locks check in __lock_downgrade()".
>> We had a revert patch shown below in the past.
>
> We had a revert in the stable trees, but that revert was incorrect.
>
> Take a look at commit 513e1073d52e55 upstream, it patches
> __lock_set_class() (even though the subject line says
> __lock_downgrade()). So this is not a backporting error as the revert
> said it is, but is rather the intended location to be patched.
>
> If this is actually wrong, then it should be addressed upstream first.
>
Hmm, upstream has two commits with same author, same date, same subject, different hash, different content.
I couldn't find from https://lkml.kernel.org/r/1547093005-26085-1-git-send-email-longman@redhat.com that
we want to patch both __lock_set_class() and __lock_downgrade(), but I found that the tip-bot has patched
__lock_downgrade() on "2019-01-21 11:29" and __lock_set_class() on "2019-02-04 8:56".
Seems that we by error patched both functions, though patching both functions should be harmless...
64aa348ed kernel/lockdep.c (Peter Zijlstra 2008-08-11 09:30:21 +0200 4115) static int
00ef9f734 kernel/lockdep.c (Peter Zijlstra 2008-12-04 09:00:17 +0100 4116) __lock_set_class(struct lockdep_map *lock, const char *name,
00ef9f734 kernel/lockdep.c (Peter Zijlstra 2008-12-04 09:00:17 +0100 4117) struct lock_class_key *key, unsigned int subclass,
00ef9f734 kernel/lockdep.c (Peter Zijlstra 2008-12-04 09:00:17 +0100 4118) unsigned long ip)
64aa348ed kernel/lockdep.c (Peter Zijlstra 2008-08-11 09:30:21 +0200 4119) {
64aa348ed kernel/lockdep.c (Peter Zijlstra 2008-08-11 09:30:21 +0200 4120) struct task_struct *curr = current;
8c8889d8e kernel/locking/lockdep.c (Imre Deak 2019-05-24 23:15:08 +0300 4121) unsigned int depth, merged = 0;
41c2c5b86 kernel/locking/lockdep.c (J. R. Okajima 2017-02-03 01:38:15 +0900 4122) struct held_lock *hlock;
64aa348ed kernel/lockdep.c (Peter Zijlstra 2008-08-11 09:30:21 +0200 4123) struct lock_class *class;
64aa348ed kernel/lockdep.c (Peter Zijlstra 2008-08-11 09:30:21 +0200 4124) int i;
64aa348ed kernel/lockdep.c (Peter Zijlstra 2008-08-11 09:30:21 +0200 4125)
513e1073d kernel/locking/lockdep.c (Waiman Long 2019-01-09 23:03:25 -0500 4126) if (unlikely(!debug_locks))
513e1073d kernel/locking/lockdep.c (Waiman Long 2019-01-09 23:03:25 -0500 4127) return 0;
513e1073d kernel/locking/lockdep.c (Waiman Long 2019-01-09 23:03:25 -0500 4128)
6419c4af7 kernel/locking/lockdep.c (J. R. Okajima 2017-02-03 01:38:17 +0900 4162) static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
6419c4af7 kernel/locking/lockdep.c (J. R. Okajima 2017-02-03 01:38:17 +0900 4163) {
6419c4af7 kernel/locking/lockdep.c (J. R. Okajima 2017-02-03 01:38:17 +0900 4164) struct task_struct *curr = current;
8c8889d8e kernel/locking/lockdep.c (Imre Deak 2019-05-24 23:15:08 +0300 4165) unsigned int depth, merged = 0;
6419c4af7 kernel/locking/lockdep.c (J. R. Okajima 2017-02-03 01:38:17 +0900 4166) struct held_lock *hlock;
6419c4af7 kernel/locking/lockdep.c (J. R. Okajima 2017-02-03 01:38:17 +0900 4167) int i;
6419c4af7 kernel/locking/lockdep.c (J. R. Okajima 2017-02-03 01:38:17 +0900 4168)
714925805 kernel/locking/lockdep.c (Waiman Long 2019-01-09 23:03:25 -0500 4169) if (unlikely(!debug_locks))
714925805 kernel/locking/lockdep.c (Waiman Long 2019-01-09 23:03:25 -0500 4170) return 0;
714925805 kernel/locking/lockdep.c (Waiman Long 2019-01-09 23:03:25 -0500 4171)
commit 513e1073d52e55b8024b4f238a48de7587c64ccf
Author: Waiman Long <longman@...hat.com>
Date: Wed Jan 9 23:03:25 2019 -0500
locking/lockdep: Add debug_locks check in __lock_downgrade()
commit 71492580571467fb7177aade19c18ce7486267f5
Author: Waiman Long <longman@...hat.com>
Date: Wed Jan 9 23:03:25 2019 -0500
locking/lockdep: Add debug_locks check in __lock_downgrade()
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