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From: Qian Cai <cai@lca.pw>
To: Petr Mladek <pmladek@suse.com>
Cc: sergey.senozhatsky.work@gmail.com, rostedt@goodmis.org,
	 peterz@infradead.org, mhocko@kernel.org, linux-mm@kvack.org,
	 john.ogness@linutronix.de, akpm@linux-foundation.org,
	david@redhat.com,  linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk()
Date: Tue, 08 Oct 2019 09:33:41 -0400	[thread overview]
Message-ID: <1570541621.5576.299.camel@lca.pw> (raw)
In-Reply-To: <20191008130803.jf3xdtyt3qpfotn5@pathway.suse.cz>

On Tue, 2019-10-08 at 15:08 +0200, Petr Mladek wrote:
> On Mon 2019-10-07 10:59:10, Qian Cai wrote:
> > It is almost impossible to eliminate all the indirect call chains from
> > console_sem/console_owner_lock to zone->lock because it is too normal that
> > something later needs to allocate some memory dynamically, so as long as it
> > directly call printk() with zone->lock held, it will be in trouble.
> 
> It is not normal the something needs to allocate memory under
> console_sem. Console drivers are supposed to get the message
> out even when the system is in really bad state and it is not
> possible to allocate memory. I consider this a bug in the console
> driver.

Again, it is not directly under console_sem. It is *indirect*.

console_sem --> lockA
lockA --> lockB
lockB --> lockC

Anything allocating memory with lockB or lockC held will form the problematic
lock chain to trigger the lockdep splat with memory offline.


      reply	other threads:[~2019-10-08 13:33 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-04 22:26 [PATCH v2] mm/page_isolation: fix a deadlock with printk() Qian Cai
2019-10-07  8:07 ` Michal Hocko
2019-10-07  9:05   ` Petr Mladek
2019-10-07 11:33     ` Michal Hocko
2019-10-07 12:34     ` Qian Cai
2019-10-07 11:04   ` Qian Cai
2019-10-07 11:37     ` Michal Hocko
2019-10-07 12:11       ` Qian Cai
2019-10-07 12:43         ` Michal Hocko
2019-10-07 13:07           ` Qian Cai
2019-10-07 14:10             ` Petr Mladek
2019-10-07 14:30 ` Petr Mladek
2019-10-07 14:49   ` Michal Hocko
2019-10-08  7:43     ` Petr Mladek
2019-10-08  8:27       ` Michal Hocko
2019-10-08 12:56         ` Christian Borntraeger
2019-10-08 16:08           ` Qian Cai
2019-10-08 18:35             ` Michal Hocko
2019-10-08 19:06               ` Qian Cai
2019-10-08 19:17                 ` Michal Hocko
2019-10-08 19:35                   ` Qian Cai
2019-10-09 11:49                     ` Petr Mladek
2019-10-09 13:06                       ` Qian Cai
2019-10-09 13:27                         ` Michal Hocko
2019-10-09 13:43                           ` Qian Cai
2019-10-09 13:51                             ` Michal Hocko
2019-10-09 14:19                               ` Qian Cai
2019-10-09 14:34                                 ` Michal Hocko
2019-10-09 15:08                                   ` Qian Cai
2019-10-09 16:23                                     ` Michal Hocko
2019-10-09 16:23                                       ` Michal Hocko
2019-10-10  9:01                                       ` Qian Cai
2019-10-10 10:59                                         ` Michal Hocko
2019-10-10 13:11                                           ` Qian Cai
2019-10-10 14:18                                             ` Michal Hocko
2019-10-10 14:47                                               ` Qian Cai
2019-10-10 17:30                                                 ` Michal Hocko
2019-10-10 17:48                                                   ` Qian Cai
2019-10-10 18:06                                                     ` Michal Hocko
2019-10-10 18:59                                                       ` David Hildenbrand
2019-10-09 14:24                             ` Petr Mladek
2019-10-09 14:46                               ` Qian Cai
2019-10-10  7:57                                 ` Petr Mladek
2019-10-09 11:39                 ` Petr Mladek
2019-10-09 13:56             ` Peter Oberparleiter
2019-10-09 14:26               ` Michal Hocko
2019-10-10  5:12                 ` Sergey Senozhatsky
2019-10-10  7:40                   ` Michal Hocko
2019-10-10  8:16                     ` Sergey Senozhatsky
2019-10-10  8:37                       ` Michal Hocko
2019-10-10  8:21                   ` Petr Mladek
2019-10-10  8:39                     ` Sergey Senozhatsky
2019-10-10 11:11                       ` Petr Mladek
2019-10-09 15:25               ` Qian Cai
2019-10-09 15:25                 ` Qian Cai
2019-10-07 14:59   ` Qian Cai
2019-10-07 15:12     ` Michal Hocko
2019-10-07 15:33       ` Qian Cai
2019-10-08  8:15         ` Petr Mladek
2019-10-08  9:32           ` Qian Cai
2019-10-08 13:13           ` Steven Rostedt
2019-10-08 13:23             ` Qian Cai
2019-10-08 13:33               ` Steven Rostedt
2019-10-08 13:42               ` Petr Mladek
2019-10-08 13:48                 ` Michal Hocko
2019-10-08 14:03                 ` Qian Cai
2019-10-08 14:08                   ` Michal Hocko
2019-10-08  8:40         ` Michal Hocko
2019-10-08 10:04           ` Qian Cai
2019-10-08 10:39             ` Michal Hocko
2019-10-08 12:00               ` Qian Cai
2019-10-08 12:39                 ` Michal Hocko
2019-10-08 13:06                   ` Qian Cai
2019-10-08 13:37                     ` Michal Hocko
2019-10-08 13:08     ` Petr Mladek
2019-10-08 13:33       ` Qian Cai [this message]

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