linux-kernel - Re: [RFC][PATCH 5/5] sched: Add ttwu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <99643c17-80ba-4910-8238-3674d583c401@arm.com>
Date: Mon, 16 Jun 2025 10:16:46 +0200
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: mingo@...hat.com, juri.lelli@...hat.com, vincent.guittot@...aro.org,
 rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
 vschneid@...hat.com, clm@...a.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 5/5] sched: Add ttwu_queue support for delayed tasks

On 13/06/2025 12:46, Peter Zijlstra wrote:
> On Fri, Jun 13, 2025 at 11:51:19AM +0200, Peter Zijlstra wrote:
>> On Fri, Jun 13, 2025 at 09:34:22AM +0200, Dietmar Eggemann wrote:
>>> On 20/05/2025 11:45, Peter Zijlstra wrote:

[...]

>>> I always get this fairly early with TTWU_QUEUE_DELAYED enabled, related
>>> to p->pi_lock not held in wakeup from interrupt.
>>>
>>> [   36.175285] WARNING: CPU: 0 PID: 162 at kernel/sched/core.c:679 __task_rq_lock+0xf8/0x128
>>
>> Thanks, let me go have a look.
> 
> I'm thinking this should cure things.
> 
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -677,7 +677,12 @@ struct rq *__task_rq_lock(struct task_st
>  {
>  	struct rq *rq;
>  
> -	lockdep_assert_held(&p->pi_lock);
> +	/*
> +	 * TASK_WAKING is used to serialize the remote end of wakeup, rather
> +	 * than p->pi_lock.
> +	 */
> +	lockdep_assert(p->__state == TASK_WAKING ||
> +		       lockdep_is_held(&p->pi_lock) != LOCK_STATE_NOT_HELD);
>  
>  	for (;;) {
>  		rq = task_rq(p);

Yes, it does. I assume we can only end up in sched_ttwu_pending()'s 'if
(unlikely(p_rq != rq))' when ttwu_queue_wakelist() is called from
ttwu_runnable(), i.e. for sched_delayed tasks.