linux-kernel - Re: [PATCH] lockdep: suggest the fix for "lockdep bfs error:-1" on print_bfs

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Message-ID: <706a4fd7-e0b0-4ada-b269-04978b0a5265@redhat.com>
Date: Mon, 29 Jul 2024 13:22:25 -0400
From: Waiman Long <longman@...hat.com>
To: "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
 Boqun Feng <boqun.feng@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lockdep: suggest the fix for "lockdep bfs error:-1" on
 print_bfs_bug


On 7/29/24 12:53, Luis Claudio R. Goncalves wrote:
> On Fri, Jul 26, 2024 at 02:24:28PM -0700, Boqun Feng wrote:
>> On Thu, Jul 25, 2024 at 03:45:57PM -0300, Luis Claudio R. Goncalves wrote:
>>> When lockdep fails while performing the Breadth-first-search operation
>>> due to lack of memory, hint that increasing the value of the configuration
>>> switch LOCKDEP_CIRCULAR_QUEUE_BITS should fix the warning.
>>>
>>> Preface the scary bactrace with the suggestion:
>>>
>>>      [  163.849242] Increase LOCKDEP_CIRCULAR_QUEUE_BITS to avoid this warning:
>>>      [  163.849248] ------------[ cut here ]------------
>>>      [  163.849250] lockdep bfs error:-1
>>>      [  163.849263] WARNING: CPU: 24 PID: 2454 at kernel/locking/lockdep.c:2091 print_bfs_bug+0x27/0x40
>>>      ...
>>>
>>> Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@...hat.com>
>>> ---
>>>   kernel/locking/lockdep.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
>>> index 58c88220a478a..1cf6d9fdddc9c 100644
>>> --- a/kernel/locking/lockdep.c
>>> +++ b/kernel/locking/lockdep.c
>>> @@ -2067,6 +2067,9 @@ static noinline void print_bfs_bug(int ret)
>>>   	/*
>>>   	 * Breadth-first-search failed, graph got corrupted?
>>>   	 */
>>> +	if (ret  == BFS_EQUEUEFULL)
>> This line has an extra space after "ret", but otherwise it looks fine.
> Should I send a v2 of the patch with the extra whitespace removed?
>
> Luis

Yes, you should. Other than the extra space, the patch looks good to me too.

Reviewed-by: Waiman Long <longman@...hat.com>

You can also add our review-by tags in your v2 patch.

Cheers,
Longman

>
>> Reviewed-by: Boqun Feng <boqun.feng@...il.com>
>>
>> Regards,
>> Boqun
>>
>>> +		pr_warn("Increase LOCKDEP_CIRCULAR_QUEUE_BITS to avoid this warning:\n");
>>> +
>>>   	WARN(1, "lockdep bfs error:%d\n", ret);
>>>   }
>>>   
>>> -- 
>>> 2.45.2
>>>
> ---end quoted text---
>