From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@kernel.org, torvalds@linux-foundation.org,
tglx@linutronix.de, ilya.dryomov@inktank.com,
umgwanakikbuti@gmail.com, linux-kernel@vger.kernel.org,
Eric Paris <eparis@parisplace.org>,
John McCutchan <john@johnmccutchan.com>,
Robert Love <rlove@rlove.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.cz>
Subject: Re: [RFC][PATCH 1/7] wait: Provide infrastructure to deal with nested blocking
Date: Mon, 4 Aug 2014 20:35:00 +0200 [thread overview]
Message-ID: <20140804183500.GA20127@redhat.com> (raw)
In-Reply-To: <20140804134455.GT19379@twins.programming.kicks-ass.net>
On 08/04, Peter Zijlstra wrote:
>
> I just noticed that poll_schedule_timeout() uses set_mb() for clearing
> its triggered variable. But I'm not entirely sure I see why..
At least we need to ensure that this "pwq->triggered = 0" can't be reordered
after the next ->poll() returns 0. In this case we should sleep unless pollwake()
was called and it set "->triggered = 1". So without this mb() we can miss an
event.
But I can hardly understand the "data written before wake up is always visible
after wake up" part... Probably this means that if we didn't actually sleep
because pwq->triggered == 1 we need to ensure that the next ->poll(file) should
see all changes which were the reason for wakeup.
Oleg.
next prev parent reply other threads:[~2014-08-04 18:37 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-04 10:30 [RFC][PATCH 0/7] nested sleeps, fixes and debug infra Peter Zijlstra
2014-08-04 10:30 ` [RFC][PATCH 1/7] wait: Provide infrastructure to deal with nested blocking Peter Zijlstra
2014-08-04 13:44 ` Peter Zijlstra
2014-08-04 18:35 ` Oleg Nesterov [this message]
2014-08-04 10:30 ` [RFC][PATCH 2/7] wait: Provide Peter Zijlstra
2014-08-04 10:30 ` [RFC][PATCH 3/7] exit: Desl with nested sleeps Peter Zijlstra
2014-08-04 18:53 ` Oleg Nesterov
2014-08-04 10:30 ` [RFC][PATCH 4/7] inotify: Deal " Peter Zijlstra
2014-08-04 19:23 ` Oleg Nesterov
2014-08-04 21:02 ` Peter Zijlstra
2014-08-05 2:22 ` Lai Jiangshan
2014-08-05 7:28 ` Peter Zijlstra
2014-08-04 10:30 ` [RFC][PATCH 5/7] tty: " Peter Zijlstra
2014-08-05 23:29 ` Greg Kroah-Hartman
2014-08-04 10:30 ` [RFC][PATCH 6/7] smp: Correctly deal " Peter Zijlstra
2014-08-04 10:30 ` [RFC][PATCH 7/7] sched: Debug " Peter Zijlstra
2014-08-05 8:33 ` [RFC][PATCH 0/7] nested sleeps, fixes and debug infra Ilya Dryomov
2014-08-05 8:33 ` Ilya Dryomov
2014-08-05 13:06 ` Peter Zijlstra
2014-08-06 7:51 ` Ilya Dryomov
2014-08-06 7:51 ` Ilya Dryomov
2014-08-06 8:31 ` Peter Zijlstra
2014-08-06 21:16 ` David Miller
2014-08-06 21:16 ` David Miller
2014-08-07 8:10 ` Peter Zijlstra
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