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From: Peter Zijlstra <peterz@infradead.org>
To: riel@redhat.com
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
	prarit@redhat.com, oleg@redhat.com, sgruszka@redhat.com
Subject: Re: [PATCH -tip 0/2] fix lock inversion in lockless sys_times()
Date: Sun, 14 Sep 2014 11:22:00 +0200	[thread overview]
Message-ID: <20140914092200.GQ346@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <1410527535-9814-1-git-send-email-riel@redhat.com>

On Fri, Sep 12, 2014 at 09:12:13AM -0400, riel@redhat.com wrote:
> The sig->stats_lock nests inside the tasklist_lock and the
> sighand->siglock in __exit_signal and wait_task_zombie.
> 
> However, both of those locks can be taken from irq context,
> which means we need to use the interrupt safe variant of
> read_seqbegin_or_lock. This blocks interrupts when the "lock"
> branch is taken (seq is odd), preventing the lock inversion.
> 
> On the first (lockless) pass through the loop, irqs are not
> blocked.
> 
> This fixes the lockdep complaints that Stanislaw reported.
> 

Thanks Rik

      parent reply	other threads:[~2014-09-14  9:22 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-12 13:12 [PATCH -tip 0/2] fix lock inversion in lockless sys_times() riel
2014-09-12 13:12 ` [PATCH -tip 1/2] seqlock: add irqsave variant of read_seqbegin_or_lock riel
2014-09-19 11:44   ` [tip:sched/core] seqlock: Add irqsave variant of read_seqbegin_or_lock() tip-bot for Rik van Riel
2014-09-12 13:12 ` [PATCH -tip 2/2] sched,time: fix lock inversion in thread_group_cputime riel
2014-09-19 11:44   ` [tip:sched/core] sched, time: Fix lock inversion in thread_group_cputime() tip-bot for Rik van Riel
2014-09-14  9:22 ` Peter Zijlstra [this message]

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