linux-kernel - Re: [RFC][PATCH 5/5] sched: Reduce ttwu rq->lock contention

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: <AANLkTimXyic51Qhe_WsfFBwAw10AKdB7e-Z2q0oLRYKP@mail.gmail.com>
Date:	Fri, 17 Dec 2010 11:06:19 +0800
From:	"Yan, Zheng" <zheng.z.yan@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Chris Mason <chris.mason@...cle.com>,
	Frank Rowand <frank.rowand@...sony.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>, Paul Turner <pjt@...gle.com>,
	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 5/5] sched: Reduce ttwu rq->lock contention

On Fri, Dec 17, 2010 at 4:32 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> @@ -953,7 +955,7 @@ static inline struct rq *__task_rq_lock(
>        for (;;) {
>                rq = task_rq(p);
>                raw_spin_lock(&rq->lock);
> -               if (likely(rq == task_rq(p)))
> +               if (likely(rq == task_rq(p)) && !task_is_waking(p))
>                        return rq;
>                raw_spin_unlock(&rq->lock);
>        }
> @@ -973,7 +975,7 @@ static struct rq *task_rq_lock(struct ta
>                local_irq_save(*flags);
>                rq = task_rq(p);
>                raw_spin_lock(&rq->lock);
> -               if (likely(rq == task_rq(p)))
> +               if (likely(rq == task_rq(p)) && !task_is_waking(p))
>                        return rq;
>                raw_spin_unlock_irqrestore(&rq->lock, *flags);
>        }

Looks like nothing prevents ttwu() from changing task's CPU while
some one else is holding task_rq_lock(). Is this OK?

Thanks
Yan, Zheng
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/