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From: Petr Mladek <pmladek@suse.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, Tejun Heo <tj@kernel.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	akpm@linux-foundation.org, linux-mm@kvack.org,
	Cong Wang <xiyou.wangcong@gmail.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Mel Gorman <mgorman@suse.de>, Michal Hocko <mhocko@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Jan Kara <jack@suse.cz>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	rostedt@home.goodmis.org, Byungchul Park <byungchul.park@lge.com>,
	Pavel Machek <pavel@ucw.cz>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup
Date: Thu, 11 Jan 2018 12:50:59 +0100	[thread overview]
Message-ID: <20180111115059.GA24419@linux.suse> (raw)
In-Reply-To: <20180111103845.GB477@jagdpanzerIV>

On Thu 2018-01-11 19:38:45, Sergey Senozhatsky wrote:
> On (01/11/18 10:34), Petr Mladek wrote:
> [..]
> > > except that handing off a console_sem to atomic task when there
> > > is   O(logbuf) > watchdog_thresh   is a regression, basically...
> > > it is what it is.
> > 
> > How this could be a regression? Is not the victim that handles
> > other printk's random? What protected the atomic task to
> > handle the other printks before this patch?
> 
> the non-atomic -> atomic context console_sem transfer. we previously
> would have kept the console_sem owner to its non-atomic owner. we now
> will make sure that if printk from atomic context happens then it will
> make it to console_unlock() loop.
> emphasis on O(logbuf) > watchdog_thresh.

Sergey, please, why do you completely and repeatedly ignore that
argument about statistical effects?

Yes, the above scenario is possible. But Steven's patch might also move the
owner from atomic context to a non-atomic one. The chances should be
more or less equal. The main advantage is that the owner is moved.
This should statistically lower the chance of a soft-lockup.

> 
> > Or do you have a system that started to suffer from softlockups
> > with this patchset and did not do this before?
> [..]
> > Do you know about any system where this patch made the softlockup
> > deterministically or statistically more likely, please?
> 
> I have explained many, many times why my boards die just like before.
> why would I bother collecting any numbers...

Is it with your own printk stress tests or during "normal" work?

If it is during a normal work, is there any chance that we
could have a look at the logs?

Best Regards,
Petr

WARNING: multiple messages have this Message-ID (diff)
From: Petr Mladek <pmladek@suse.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, Tejun Heo <tj@kernel.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	akpm@linux-foundation.org, linux-mm@kvack.org,
	Cong Wang <xiyou.wangcong@gmail.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Mel Gorman <mgorman@suse.de>, Michal Hocko <mhocko@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Jan Kara <jack@suse.cz>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	rostedt@home.goodmis.org, Byungchul Park <byungchul.park@lge.com>,
	Pavel Machek <pavel@ucw.cz>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup
Date: Thu, 11 Jan 2018 12:50:59 +0100	[thread overview]
Message-ID: <20180111115059.GA24419@linux.suse> (raw)
In-Reply-To: <20180111103845.GB477@jagdpanzerIV>

On Thu 2018-01-11 19:38:45, Sergey Senozhatsky wrote:
> On (01/11/18 10:34), Petr Mladek wrote:
> [..]
> > > except that handing off a console_sem to atomic task when there
> > > is   O(logbuf) > watchdog_thresh   is a regression, basically...
> > > it is what it is.
> > 
> > How this could be a regression? Is not the victim that handles
> > other printk's random? What protected the atomic task to
> > handle the other printks before this patch?
> 
> the non-atomic -> atomic context console_sem transfer. we previously
> would have kept the console_sem owner to its non-atomic owner. we now
> will make sure that if printk from atomic context happens then it will
> make it to console_unlock() loop.
> emphasis on O(logbuf) > watchdog_thresh.

Sergey, please, why do you completely and repeatedly ignore that
argument about statistical effects?

Yes, the above scenario is possible. But Steven's patch might also move the
owner from atomic context to a non-atomic one. The chances should be
more or less equal. The main advantage is that the owner is moved.
This should statistically lower the chance of a soft-lockup.

> 
> > Or do you have a system that started to suffer from softlockups
> > with this patchset and did not do this before?
> [..]
> > Do you know about any system where this patch made the softlockup
> > deterministically or statistically more likely, please?
> 
> I have explained many, many times why my boards die just like before.
> why would I bother collecting any numbers...

Is it with your own printk stress tests or during "normal" work?

If it is during a normal work, is there any chance that we
could have a look at the logs?

Best Regards,
Petr

--
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  reply	other threads:[~2018-01-11 11:51 UTC|newest]

Thread overview: 280+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-10 13:24 [PATCH v5 0/2] printk: Console owner and waiter logic cleanup Petr Mladek
2018-01-10 13:24 ` Petr Mladek
2018-01-10 13:24 ` [PATCH v5 1/2] printk: Add console owner and waiter logic to load balance console writes Petr Mladek
2018-01-10 13:24   ` Petr Mladek
2018-01-10 16:50   ` Steven Rostedt
2018-01-10 16:50     ` Steven Rostedt
2018-01-12 16:54   ` Steven Rostedt
2018-01-12 16:54     ` Steven Rostedt
2018-01-12 17:11     ` Steven Rostedt
2018-01-12 17:11       ` Steven Rostedt
2018-01-17 19:13       ` Rasmus Villemoes
2018-01-17 19:13         ` Rasmus Villemoes
2018-01-17 19:33         ` Steven Rostedt
2018-01-17 19:33           ` Steven Rostedt
2018-01-19  9:51         ` Sergey Senozhatsky
2018-01-19  9:51           ` Sergey Senozhatsky
2018-01-18 22:03     ` Pavel Machek
2018-01-18 22:03       ` Pavel Machek
2018-01-19  0:20       ` Steven Rostedt
2018-01-19  0:20         ` Steven Rostedt
2018-01-17  2:19   ` Byungchul Park
2018-01-17  2:19     ` Byungchul Park
2018-01-17  4:54     ` Byungchul Park
2018-01-17  4:54       ` Byungchul Park
2018-01-17  7:34     ` Byungchul Park
2018-01-17  7:34       ` Byungchul Park
2018-01-17 12:04     ` Petr Mladek
2018-01-17 12:04       ` Petr Mladek
2018-01-18  1:53       ` Byungchul Park
2018-01-18  1:53         ` Byungchul Park
2018-01-18  1:57         ` Byungchul Park
2018-01-18  1:57           ` Byungchul Park
2018-01-18  2:19         ` Steven Rostedt
2018-01-18  2:19           ` Steven Rostedt
2018-01-18  4:01           ` Byungchul Park
2018-01-18  4:01             ` Byungchul Park
2018-01-18 15:21             ` Steven Rostedt
2018-01-18 15:21               ` Steven Rostedt
2018-01-19  2:37               ` Byungchul Park
2018-01-19  2:37                 ` Byungchul Park
2018-01-19  3:27                 ` Steven Rostedt
2018-01-19  3:27                   ` Steven Rostedt
2018-01-22  2:31                   ` Byungchul Park
2018-01-22  2:31                     ` Byungchul Park
2018-01-10 13:24 ` [PATCH v5 2/2] printk: Hide console waiter logic into helpers Petr Mladek
2018-01-10 13:24   ` Petr Mladek
2018-01-10 17:52   ` Steven Rostedt
2018-01-10 17:52     ` Steven Rostedt
2018-01-11 12:03     ` Petr Mladek
2018-01-11 12:03       ` Petr Mladek
2018-01-12 15:37       ` Steven Rostedt
2018-01-12 15:37         ` Steven Rostedt
2018-01-12 16:08         ` Petr Mladek
2018-01-12 16:08           ` Petr Mladek
2018-01-12 16:36           ` Steven Rostedt
2018-01-12 16:36             ` Steven Rostedt
2018-01-15 16:08             ` Petr Mladek
2018-01-15 16:08               ` Petr Mladek
2018-01-16  5:05               ` Sergey Senozhatsky
2018-01-16  5:05                 ` Sergey Senozhatsky
2018-01-10 14:05 ` [PATCH v5 0/2] printk: Console owner and waiter logic cleanup Tejun Heo
2018-01-10 14:05   ` Tejun Heo
2018-01-10 16:29   ` Petr Mladek
2018-01-10 16:29     ` Petr Mladek
2018-01-10 17:02     ` Tejun Heo
2018-01-10 17:02       ` Tejun Heo
2018-01-10 18:21       ` Peter Zijlstra
2018-01-10 18:21         ` Peter Zijlstra
2018-01-10 18:30         ` Tejun Heo
2018-01-10 18:30           ` Tejun Heo
2018-01-10 18:41           ` Peter Zijlstra
2018-01-10 18:41             ` Peter Zijlstra
2018-01-10 19:05             ` Tejun Heo
2018-01-10 19:05               ` Tejun Heo
2018-01-11  5:15         ` Sergey Senozhatsky
2018-01-11  5:15           ` Sergey Senozhatsky
2018-01-10 18:22       ` Steven Rostedt
2018-01-10 18:22         ` Steven Rostedt
2018-01-10 18:36         ` Tejun Heo
2018-01-10 18:36           ` Tejun Heo
2018-01-10 18:40       ` Mathieu Desnoyers
2018-01-10 18:40         ` Mathieu Desnoyers
2018-01-11  7:36         ` Sergey Senozhatsky
2018-01-11  7:36           ` Sergey Senozhatsky
2018-01-11 11:24           ` Petr Mladek
2018-01-11 11:24             ` Petr Mladek
2018-01-11 13:19             ` Sergey Senozhatsky
2018-01-11 13:19               ` Sergey Senozhatsky
2018-01-24  9:36       ` Peter Zijlstra
2018-01-24  9:36         ` Peter Zijlstra
2018-01-24 18:46         ` Tejun Heo
2018-01-24 18:46           ` Tejun Heo
2018-05-09  8:58       ` Sergey Senozhatsky
2018-05-09  8:58         ` Sergey Senozhatsky
2018-01-10 18:54     ` Steven Rostedt
2018-01-10 18:54       ` Steven Rostedt
2018-01-11  5:10     ` Sergey Senozhatsky
2018-01-11  5:10       ` Sergey Senozhatsky
2018-01-10 18:05   ` Steven Rostedt
2018-01-10 18:05     ` Steven Rostedt
2018-01-10 18:12     ` Tejun Heo
2018-01-10 18:12       ` Tejun Heo
2018-01-10 18:14       ` Tejun Heo
2018-01-10 18:14         ` Tejun Heo
2018-01-10 18:45         ` Steven Rostedt
2018-01-10 18:45           ` Steven Rostedt
2018-01-10 18:41       ` Steven Rostedt
2018-01-10 18:41         ` Steven Rostedt
2018-01-10 18:57         ` Tejun Heo
2018-01-10 18:57           ` Tejun Heo
2018-01-10 19:17           ` Steven Rostedt
2018-01-10 19:17             ` Steven Rostedt
2018-01-10 19:34             ` Tejun Heo
2018-01-10 19:34               ` Tejun Heo
2018-01-10 19:44               ` Steven Rostedt
2018-01-10 19:44                 ` Steven Rostedt
2018-01-10 22:44                 ` Tejun Heo
2018-01-10 22:44                   ` Tejun Heo
2018-01-11  5:35             ` Sergey Senozhatsky
2018-01-11  5:35               ` Sergey Senozhatsky
2018-01-11  4:58     ` Sergey Senozhatsky
2018-01-11  4:58       ` Sergey Senozhatsky
2018-01-11  9:34       ` Petr Mladek
2018-01-11  9:34         ` Petr Mladek
2018-01-11 10:38         ` Sergey Senozhatsky
2018-01-11 10:38           ` Sergey Senozhatsky
2018-01-11 11:50           ` Petr Mladek [this message]
2018-01-11 11:50             ` Petr Mladek
2018-01-11 16:29           ` Steven Rostedt
2018-01-11 16:29             ` Steven Rostedt
2018-01-12  1:30             ` Steven Rostedt
2018-01-12  1:30               ` Steven Rostedt
2018-01-12  2:55               ` Steven Rostedt
2018-01-12  2:55                 ` Steven Rostedt
2018-01-12  4:20                 ` Steven Rostedt
2018-01-12  4:20                   ` Steven Rostedt
2018-01-16 19:44                 ` Tejun Heo
2018-01-16 19:44                   ` Tejun Heo
2018-01-17  9:12                   ` Petr Mladek
2018-01-17  9:12                     ` Petr Mladek
2018-01-17 15:15                     ` Tejun Heo
2018-01-17 15:15                       ` Tejun Heo
2018-01-17 17:12                       ` Steven Rostedt
2018-01-17 17:12                         ` Steven Rostedt
2018-01-17 18:42                         ` Steven Rostedt
2018-01-17 18:42                           ` Steven Rostedt
2018-01-19 18:20                           ` Steven Rostedt
2018-01-19 18:20                             ` Steven Rostedt
2018-01-20  7:14                             ` Sergey Senozhatsky
2018-01-20  7:14                               ` Sergey Senozhatsky
2018-01-20 15:49                               ` Steven Rostedt
2018-01-20 15:49                                 ` Steven Rostedt
2018-01-21 14:15                                 ` Sergey Senozhatsky
2018-01-21 14:15                                   ` Sergey Senozhatsky
2018-01-21 21:04                                   ` Steven Rostedt
2018-01-21 21:04                                     ` Steven Rostedt
2018-01-22  8:56                                     ` Sergey Senozhatsky
2018-01-22  8:56                                       ` Sergey Senozhatsky
2018-01-22 10:28                                       ` Sergey Senozhatsky
2018-01-22 10:28                                         ` Sergey Senozhatsky
2018-01-22 10:36                                         ` Sergey Senozhatsky
2018-01-22 10:36                                           ` Sergey Senozhatsky
2018-01-23  6:40                                   ` Sergey Senozhatsky
2018-01-23  6:40                                     ` Sergey Senozhatsky
2018-01-23  7:05                                     ` Sergey Senozhatsky
2018-01-23  7:05                                       ` Sergey Senozhatsky
2018-01-23  7:31                                     ` Sergey Senozhatsky
2018-01-23  7:31                                       ` Sergey Senozhatsky
2018-01-23 14:56                                     ` Steven Rostedt
2018-01-23 14:56                                       ` Steven Rostedt
2018-01-23 15:21                                       ` Sergey Senozhatsky
2018-01-23 15:21                                         ` Sergey Senozhatsky
2018-01-23 15:41                                         ` Steven Rostedt
2018-01-23 15:41                                           ` Steven Rostedt
2018-01-23 15:43                                           ` Tejun Heo
2018-01-23 15:43                                             ` Tejun Heo
2018-01-23 16:12                                             ` Sergey Senozhatsky
2018-01-23 16:12                                               ` Sergey Senozhatsky
2018-01-23 16:13                                             ` Steven Rostedt
2018-01-23 16:13                                               ` Steven Rostedt
2018-01-23 17:21                                               ` Tejun Heo
2018-01-23 17:21                                                 ` Tejun Heo
2018-04-23  5:35                                             ` Sergey Senozhatsky
2018-04-23  5:35                                               ` Sergey Senozhatsky
2018-01-23 16:01                                           ` Sergey Senozhatsky
2018-01-23 16:01                                             ` Sergey Senozhatsky
2018-01-23 16:24                                             ` Steven Rostedt
2018-01-23 16:24                                               ` Steven Rostedt
2018-01-24  2:11                                               ` Sergey Senozhatsky
2018-01-24  2:11                                                 ` Sergey Senozhatsky
2018-01-24  2:52                                                 ` Steven Rostedt
2018-01-24  2:52                                                   ` Steven Rostedt
2018-01-24  4:44                                                   ` Sergey Senozhatsky
2018-01-24  4:44                                                     ` Sergey Senozhatsky
2018-01-23 17:22                                             ` Tejun Heo
2018-01-23 17:22                                               ` Tejun Heo
2018-01-20 12:19                             ` Tejun Heo
2018-01-20 12:19                               ` Tejun Heo
2018-01-20 14:51                               ` Steven Rostedt
2018-01-20 14:51                                 ` Steven Rostedt
2018-01-17 20:05                         ` Tejun Heo
2018-01-17 20:05                           ` Tejun Heo
2018-01-18  5:43                           ` Sergey Senozhatsky
2018-01-18  5:43                             ` Sergey Senozhatsky
2018-01-18 11:51                           ` Petr Mladek
2018-01-18 11:51                             ` Petr Mladek
2018-01-18  5:42                         ` Sergey Senozhatsky
2018-01-18  5:42                           ` Sergey Senozhatsky
2018-01-12  3:12               ` Sergey Senozhatsky
2018-01-12  3:12                 ` Sergey Senozhatsky
2018-01-12  2:56             ` Sergey Senozhatsky
2018-01-12  2:56               ` Sergey Senozhatsky
2018-01-12  3:21               ` Steven Rostedt
2018-01-12  3:21                 ` Steven Rostedt
2018-01-12 10:05                 ` Sergey Senozhatsky
2018-01-12 10:05                   ` Sergey Senozhatsky
2018-01-12 12:21                   ` Steven Rostedt
2018-01-12 12:21                     ` Steven Rostedt
2018-01-12 12:55                     ` Petr Mladek
2018-01-12 12:55                       ` Petr Mladek
2018-01-13  7:31                       ` Sergey Senozhatsky
2018-01-13  7:31                         ` Sergey Senozhatsky
2018-01-15  8:51                         ` Petr Mladek
2018-01-15  8:51                           ` Petr Mladek
2018-01-15  9:48                           ` Sergey Senozhatsky
2018-01-15  9:48                             ` Sergey Senozhatsky
2018-01-16  5:16                           ` Sergey Senozhatsky
2018-01-16  5:16                             ` Sergey Senozhatsky
2018-01-16  9:08                             ` Petr Mladek
2018-01-16  9:08                               ` Petr Mladek
2018-01-15 12:08                       ` Steven Rostedt
2018-01-15 12:08                         ` Steven Rostedt
2018-01-16  4:51                         ` Sergey Senozhatsky
2018-01-16  4:51                           ` Sergey Senozhatsky
2018-01-13  7:28                     ` Sergey Senozhatsky
2018-01-13  7:28                       ` Sergey Senozhatsky
2018-01-15 10:17                       ` Petr Mladek
2018-01-15 10:17                         ` Petr Mladek
2018-01-15 11:50                         ` Petr Mladek
2018-01-15 11:50                           ` Petr Mladek
2018-01-16  6:10                           ` Sergey Senozhatsky
2018-01-16  6:10                             ` Sergey Senozhatsky
2018-01-16  9:36                             ` Petr Mladek
2018-01-16  9:36                               ` Petr Mladek
2018-01-16 10:10                               ` Sergey Senozhatsky
2018-01-16 10:10                                 ` Sergey Senozhatsky
2018-01-16 16:06                             ` Steven Rostedt
2018-01-16 16:06                               ` Steven Rostedt
2018-01-16  5:23                         ` Sergey Senozhatsky
2018-01-16  5:23                           ` Sergey Senozhatsky
2018-01-15 12:06                       ` Steven Rostedt
2018-01-15 12:06                         ` Steven Rostedt
2018-01-15 14:45                         ` Petr Mladek
2018-01-15 14:45                           ` Petr Mladek
2018-01-16  2:23                           ` Sergey Senozhatsky
2018-01-16  2:23                             ` Sergey Senozhatsky
2018-01-16  4:47                             ` Sergey Senozhatsky
2018-01-16  4:47                               ` Sergey Senozhatsky
2018-01-16 10:19                               ` Petr Mladek
2018-01-16 10:19                                 ` Petr Mladek
2018-01-17  2:24                                 ` Sergey Senozhatsky
2018-01-17  2:24                                   ` Sergey Senozhatsky
2018-01-16 15:45                               ` Steven Rostedt
2018-01-16 15:45                                 ` Steven Rostedt
2018-01-17  2:18                                 ` Sergey Senozhatsky
2018-01-17  2:18                                   ` Sergey Senozhatsky
2018-01-17 13:04                                   ` Petr Mladek
2018-01-17 13:04                                     ` Petr Mladek
2018-01-17 15:24                                     ` Steven Rostedt
2018-01-17 15:24                                       ` Steven Rostedt
2018-01-18  4:31                                     ` Sergey Senozhatsky
2018-01-18  4:31                                       ` Sergey Senozhatsky
2018-01-18 15:22                                       ` Steven Rostedt
2018-01-18 15:22                                         ` Steven Rostedt
2018-01-16 10:13                             ` Petr Mladek
2018-01-16 10:13                               ` Petr Mladek
2018-01-17  6:29                               ` Sergey Senozhatsky
2018-01-17  6:29                                 ` Sergey Senozhatsky
2018-01-16  1:46                         ` Sergey Senozhatsky
2018-01-16  1:46                           ` Sergey Senozhatsky

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