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From: "H. Peter Anvin" <hpa@zytor.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Len Brown <lenb@kernel.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
	linux-next@vger.kernel.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: linux-next: build failure after merge of the tip tree
Date: Mon, 20 Jan 2014 03:00:29 -0800
Message-ID: <52DD01CD.9030809@zytor.com> (raw)
In-Reply-To: <20140120095532.GX31570@twins.programming.kicks-ass.net>

On 01/20/2014 01:55 AM, Peter Zijlstra wrote:
> 
> Ok, so I still don't get the problem of enabling interrupts early.
> 
> If we enable them early we can get interrupts; which afaict fall into
> two groups, those that do and do not set NEED_RESCHED.
> 
> For those that do not set NEED_RESCHED, we'd have woken from MWAIT/HLT
> and looped right back into it, so receiving those early -- before
> actually calling MWAIT/HLT seems like a NO-OP.

The description for commit d331e739f5ad seems to indicate otherwise:

    Idle callbacks has some races when enter_idle() sets isidle and
subsequent
    interrupts that can happen on that CPU, before CPU goes to idle. Due
to this,
    an IDLE_END can get called before IDLE_START. To avoid these races,
disable
    interrupts before enter_idle and make sure that all idle routines do not
    enable interrupts before entering idle.

This implies to me that once we have set isidle, if we take an interrupt
we *have* to drop out of the idle routine.

> For those setting NEED_RESCHED, we test NEED_RESCHED in all the right
> places.
> 
>  - current_set_polling_and_test(), we test need_resched after telling
>    remote CPUs they don't need to send interrupts because we're polling
>    for it -- the remote cpus set NEED_RESCHED before testing if we're
>    polling for it.
> 
>  - we test NEED_RESCHED after setting up the monitor and before calling
>    MWAIT. Therefore, if an interrupt would happen right before we call
>    MWAIT, the monitor is already set and the MWAIT does an immediate
>    exit.
> 
> AFAICT we simply cannot get stuck and miss a NEED_RESCHED this way.
> 

Well, it is obviously needed for the HLT case.  For MWAIT it seems like
the MONITOR should have gotten disarmed and therefore MWAIT shouldn't
sleep... I don't know off the top of my head if there are any errata in
that department and/or if there are any other issues.

	-hpa

  reply index

Thread overview: 245+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-16  3:58 Stephen Rothwell
2014-01-16 12:19 ` Peter Zijlstra
2014-01-16 20:46   ` Stephen Rothwell
2014-01-16 22:25     ` Peter Zijlstra
2014-01-16 22:34       ` Stephen Rothwell
2014-01-16 22:51         ` H. Peter Anvin
2014-01-17  3:45           ` Stephen Rothwell
2014-01-18  9:46             ` Mike Galbraith
2014-01-18 12:44               ` Peter Zijlstra
2014-01-18 14:06                 ` Sabrina Dubroca
2014-01-18 15:21                 ` Mike Galbraith
2014-01-18 19:14                   ` H. Peter Anvin
2014-01-18 21:54                     ` Peter Zijlstra
2014-01-20  3:51               ` Stephen Rothwell
2014-01-20  8:42                 ` Sedat Dilek
2014-01-20  8:46                   ` Sedat Dilek
2014-01-20 13:10                     ` Stephen Rothwell
2014-01-20 15:28                       ` Sedat Dilek
2014-01-20  9:17                   ` Mike Galbraith
2014-01-20  9:25                     ` Sedat Dilek
2014-01-20  9:48                       ` Mike Galbraith
2014-01-20  4:45     ` Len Brown
2014-01-20  8:26       ` Peter Zijlstra
2014-01-20  8:56         ` H. Peter Anvin
2014-01-20  9:16           ` Peter Zijlstra
2014-01-20  9:23             ` H. Peter Anvin
2014-01-20  9:29               ` Ingo Molnar
2014-01-20 21:39                 ` Len Brown
2014-01-20 21:51                   ` Peter Zijlstra
2014-01-21  3:26                     ` Mike Galbraith
2014-01-21 10:47                     ` Ingo Molnar
2014-01-20  9:55               ` Peter Zijlstra
2014-01-20 11:00                 ` H. Peter Anvin [this message]
2014-01-20 11:05                   ` Peter Zijlstra
2014-01-16 20:56   ` H. Peter Anvin
2014-01-20  1:00 ` Len Brown
2014-01-20  1:07   ` H. Peter Anvin
2014-01-20  8:30   ` Peter Zijlstra
2014-01-20 10:13     ` Peter Zijlstra
2014-01-20 10:19       ` H. Peter Anvin
2014-01-20 11:06         ` Peter Zijlstra
  -- strict thread matches above, loose matches on Subject: below --
2019-11-21  3:54 Stephen Rothwell
2019-11-21  8:36 ` Peter Zijlstra
2019-11-21 18:37 ` Alex Deucher
2019-11-18  3:11 Stephen Rothwell
2019-11-18  9:49 ` Jiri Slaby
2019-11-18 12:49 ` Borislav Petkov
2019-10-21  2:13 Stephen Rothwell
2019-10-21  5:51 ` Ingo Molnar
2019-10-21  6:37   ` Stephen Rothwell
2019-10-10  2:14 Stephen Rothwell
2019-10-10  8:02 ` Ingo Molnar
2019-10-10 11:23   ` Stephen Rothwell
2019-10-10 13:44     ` Daniel Vetter
2019-11-06  2:53 ` Stephen Rothwell
2019-11-27 23:39   ` Stephen Rothwell
2019-08-29  6:20 Stephen Rothwell
2019-08-29  7:46 ` Peter Zijlstra
2019-08-29 12:24   ` Thomas Gleixner
2019-08-29 13:04     ` Peter Zijlstra
2019-08-08  4:48 Stephen Rothwell
2019-08-01  3:38 Stephen Rothwell
2019-07-09  6:54 Stephen Rothwell
2019-07-10  0:01 ` Stephen Rothwell
2019-07-10 18:21   ` Ilya Dryomov
2019-07-10 21:38     ` Stephen Rothwell
2019-07-02  5:33 Stephen Rothwell
2019-07-02 10:28 ` David Sterba
2019-07-02 12:57   ` Stephen Rothwell
2019-07-08  6:50   ` Stephen Rothwell
2019-06-25  6:04 Stephen Rothwell
2019-06-25  6:23 ` Kalle Valo
2019-06-25  6:26   ` Thomas Gleixner
2019-06-25  6:36   ` Stephen Rothwell
2019-06-25  6:51     ` Kalle Valo
2019-06-25  6:56     ` Thomas Gleixner
2019-06-25  7:47       ` Kalle Valo
2019-07-09  0:09 ` Stephen Rothwell
2019-07-09  3:46 ` Stephen Rothwell
2018-11-06  0:43 Stephen Rothwell
2018-08-08 23:24 Stephen Rothwell
2018-08-09  9:41 ` Joerg Roedel
2018-04-03  5:41 Stephen Rothwell
2018-04-03  9:30 ` Peter Zijlstra
2018-04-03 12:39 ` David Howells
2018-04-03 12:42   ` Peter Zijlstra
2018-04-03 12:41 ` David Howells
2017-11-08  2:47 Stephen Rothwell
2017-11-08  3:01 ` Josh Poimboeuf
2017-11-08  7:35   ` Stephen Rothwell
2017-11-08  9:18   ` Ingo Molnar
2017-11-08 12:14     ` Stephen Rothwell
2017-11-09  6:18       ` Ingo Molnar
2017-11-08 13:17     ` Josh Poimboeuf
2017-11-09  3:03     ` Stephen Rothwell
2017-11-01 10:51 Stephen Rothwell
2017-11-01 14:32 ` Kees Cook
2017-06-28  3:43 Stephen Rothwell
2017-06-28  4:00 ` jeffy
2017-06-28  4:24   ` Stephen Rothwell
2017-07-03  3:01 ` Stephen Rothwell
2017-05-02  3:17 Stephen Rothwell
2017-04-24  3:32 Stephen Rothwell
2017-04-24  5:31 ` Ingo Molnar
2017-04-05  3:36 Stephen Rothwell
2017-04-05  7:24 ` Mikko Perttunen
2016-12-07  1:37 Stephen Rothwell
2016-12-07  7:45 ` Ingo Molnar
2016-12-07  8:12   ` Jiri Olsa
2016-12-07 14:49     ` Arnaldo Carvalho de Melo
2016-12-07 18:56       ` Ingo Molnar
2016-12-07 20:32         ` Stephen Rothwell
2016-11-17  3:22 Stephen Rothwell
2016-09-29  3:20 Stephen Rothwell
2016-09-29 12:25 ` Rafael J. Wysocki
2016-09-29 15:54   ` Chen, Yu C
2016-09-29 20:50     ` Rafael J. Wysocki
2016-09-21  3:23 Stephen Rothwell
2016-09-21  6:44 ` Viresh Kumar
2016-07-18  8:29 Stephen Rothwell
2016-07-18 14:27 ` Paul Gortmaker
2016-07-18  5:15 Stephen Rothwell
2016-04-18  3:03 Stephen Rothwell
2016-04-14  2:14 Stephen Rothwell
2016-04-14 12:35 ` Arnaldo Carvalho de Melo
2016-04-14 12:55   ` Michael Ellerman
2016-04-14 15:08     ` Arnaldo Carvalho de Melo
2016-04-15 21:15 ` Arnaldo Carvalho de Melo
2016-04-15 21:28   ` Arnaldo Carvalho de Melo
2016-04-17 12:12     ` Jiri Olsa
2016-04-17 13:04       ` Jiri Olsa
2016-04-18 13:24         ` Arnaldo Carvalho de Melo
2016-04-18 13:28           ` Jiri Olsa
2016-03-01  1:29 Stephen Rothwell
2016-03-01  7:07 ` Ingo Molnar
2016-03-01  7:28   ` Sedat Dilek
2016-03-01  7:39     ` H. Peter Anvin
2016-03-01  8:41       ` Sedat Dilek
2016-03-01  9:45       ` Ingo Molnar
2016-03-01  9:40   ` Stephen Rothwell
2015-09-16  1:30 Stephen Rothwell
2015-09-16  4:53 ` David Miller
2015-09-16  0:12 Stephen Rothwell
2015-09-16  6:16 ` Jiri Olsa
2015-09-16  6:38   ` Jiri Olsa
2015-09-16  7:30     ` Stephen Rothwell
2015-09-16 14:17       ` Arnaldo Carvalho de Melo
2015-09-17  0:34   ` Stephen Rothwell
2015-09-30  2:56     ` Stephen Rothwell
2015-09-30  6:08       ` Jiri Olsa
2015-09-30  6:17         ` Stephen Rothwell
2015-07-28  5:33 Stephen Rothwell
2015-07-28 16:34 ` Luis R. Rodriguez
2015-07-28 18:17   ` Luis R. Rodriguez
2015-07-28  2:43 Stephen Rothwell
2015-07-28  8:41 ` Sudeep Holla
2015-07-28  9:43   ` Gregory CLEMENT
2015-07-15  1:01 Stephen Rothwell
2015-07-08  0:56 Stephen Rothwell
2015-07-08  9:40 ` Thomas Gleixner
2015-06-12 10:51 Michael Ellerman
     [not found] ` <BY1PR0701MB17063C25D627AF725A9E0D46FEBB0@BY1PR0701MB1706.namprd07.prod.outlook.com>
2015-06-12 21:22   ` David Miller
2015-06-12 21:25     ` Chickles, Derek
2015-06-09  7:15 Stephen Rothwell
2015-04-07  7:18 Stephen Rothwell
2015-04-07  8:48 ` Ingo Molnar
2015-04-07  8:56   ` Daniel Borkmann
2015-04-07  9:05     ` Stephen Rothwell
2015-04-07 11:13       ` Daniel Borkmann
2015-04-07 16:18         ` Alexei Starovoitov
2015-04-07 19:54           ` Daniel Borkmann
2015-04-08  5:03             ` Stephen Rothwell
2015-04-15  1:25               ` Stephen Rothwell
2015-04-07  8:53 ` Peter Zijlstra
2015-03-30  6:13 Stephen Rothwell
2015-03-30  7:15 ` Russell King - ARM Linux
2015-03-30  8:08   ` Stephen Rothwell
2015-03-30 14:57     ` Nathan Lynch
2015-03-30 15:08       ` Russell King - ARM Linux
2015-03-30 15:24         ` Nathan Lynch
2015-04-13 23:34         ` Stephen Rothwell
2014-07-25  4:45 Stephen Rothwell
2014-07-29 23:56 ` Stephen Rothwell
2014-07-30  3:10   ` John Stultz
2014-06-04  6:05 Stephen Rothwell
2014-06-04 10:49 ` Thomas Gleixner
2014-06-04 14:46   ` Linus Torvalds
2014-06-04 16:23   ` Olof Johansson
2014-06-04 20:02     ` Thomas Gleixner
2014-05-23  7:14 Stephen Rothwell
2014-05-29  1:38 ` Stephen Rothwell
2014-04-24  3:51 Stephen Rothwell
2014-02-12  2:41 Stephen Rothwell
2014-02-12  4:48 ` Preeti U Murthy
2014-02-11  3:00 Stephen Rothwell
2014-01-14  3:26 Stephen Rothwell
2014-01-14 14:14 ` Peter Zijlstra
2014-01-14 19:06   ` Mikulas Patocka
2014-01-14 20:05     ` Peter Zijlstra
2014-01-14 21:43       ` Mikulas Patocka
2014-01-14 22:03         ` Rafael J. Wysocki
2014-01-14 21:52           ` Mikulas Patocka
2014-01-14 22:18             ` Rafael J. Wysocki
2014-01-16 12:14         ` Peter Zijlstra
2013-10-28  9:24 Stephen Rothwell
2013-10-28 10:18 ` Thierry Reding
2013-10-28 10:26   ` Ingo Molnar
2013-10-29  6:00     ` Stephen Rothwell
2013-04-29  5:45 Stephen Rothwell
2013-02-14  2:30 Stephen Rothwell
2013-02-21  2:04 ` Stephen Rothwell
2013-02-02  5:04 Stephen Rothwell
2012-08-16  3:12 Stephen Rothwell
2012-08-16 19:46 ` Paul E. McKenney
2012-08-17  0:56   ` Stephen Rothwell
2012-08-17 11:50     ` Paul E. McKenney
2012-08-20  4:54       ` Stephen Rothwell
2012-08-20 15:09         ` Paul E. McKenney
2012-03-08  4:21 Stephen Rothwell
2012-03-08 18:00 ` Greg KH
2012-03-20 22:00   ` Stephen Rothwell
2012-03-20 22:32     ` Greg KH
2012-03-21  9:53     ` Alan Cox
2012-03-21 12:19     ` Alan Cox
2012-03-21 12:29       ` Stephen Rothwell
2012-02-24  3:47 Stephen Rothwell
2012-02-24  3:34 Stephen Rothwell
2011-10-05  6:25 Stephen Rothwell
2011-10-05  8:46 ` Peter Zijlstra
2011-10-11  6:15   ` Stephen Rothwell
2011-06-27  4:22 Stephen Rothwell
2011-06-28 10:55 ` Stijn Devriendt
2011-04-01  2:00 Stephen Rothwell
2011-01-31  4:42 Stephen Rothwell
2011-02-17  3:47 ` Stephen Rothwell
2011-02-17 13:18   ` Michal Marek
2011-02-17 15:02     ` Michal Marek
2011-02-17 17:11       ` Ingo Molnar
2011-02-17 22:47       ` Stephen Rothwell
2011-02-18  3:54         ` Stephen Rothwell
2010-10-19  5:13 Stephen Rothwell
2010-07-29  3:04 Stephen Rothwell
2010-05-10  4:49 Stephen Rothwell
2010-05-10  5:09 ` H. Peter Anvin
2010-03-12  4:00 Stephen Rothwell

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