linux-kernel - Re: [PATCH v2 1/3] sched: Avoid that __wait_on_bit

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Message-ID: <e6b146d9-bb6b-c4cc-9408-0fc77a612d1d@acm.org>
Date:	Sat, 6 Aug 2016 14:36:10 -0700
From:	Bart Van Assche <bvanassche@....org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Neil Brown <neilb@...e.de>,
	Michael Shaver <jmshaver@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] sched: Avoid that __wait_on_bit_lock() hangs

On 08/05/16 16:09, Bart Van Assche wrote:
> If delivery of a signal and __wake_up_common() happen concurrently
> it is possible that the signal is delivered after __wake_up_common()
> woke up the affected task and before bit_wait_io() checks whether a
> signal is pending. Avoid that the next waiter is not woken up if this
> happens.

(replying to my own e-mail)

Although this patch works reliably in my tests, the above description 
does not explain the hang. I will resend this patch with a better 
description.

Bart.