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From: Michal Hocko <mhocko@kernel.org>
To: Qian Cai <cai@lca.pw>
Cc: Petr Mladek <pmladek@suse.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	sergey.senozhatsky.work@gmail.com, rostedt@goodmis.org,
	peterz@infradead.org, linux-mm@kvack.org,
	john.ogness@linutronix.de, akpm@linux-foundation.org,
	Vasily Gorbik <gor@linux.ibm.com>,
	Peter Oberparleiter <oberpar@linux.ibm.com>,
	david@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk()
Date: Thu, 10 Oct 2019 16:18:20 +0200	[thread overview]
Message-ID: <20191010141820.GI18412@dhcp22.suse.cz> (raw)
In-Reply-To: <1570713112.5937.26.camel@lca.pw>

On Thu 10-10-19 09:11:52, Qian Cai wrote:
> On Thu, 2019-10-10 at 12:59 +0200, Michal Hocko wrote:
> > On Thu 10-10-19 05:01:44, Qian Cai wrote:
> > > 
> > > 
> > > > On Oct 9, 2019, at 12:23 PM, Michal Hocko <mhocko@kernel.org> wrote:
> > > > 
> > > > If this was only about the memory offline code then I would agree. But
> > > > we are talking about any printk from the zone->lock context and that is
> > > > a bigger deal. Besides that it is quite natural that the printk code
> > > > should be more universal and allow to be also called from the MM
> > > > contexts as much as possible. If there is any really strong reason this
> > > > is not possible then it should be documented at least.
> > > 
> > > Where is the best place to document this? I am thinking about under
> > > the “struct zone” definition’s lock field in mmzone.h.
> > 
> > I am not sure TBH and I do not think we have reached the state where
> > this would be the only way forward.
> 
> How about I revised the changelog to focus on memory offline rather than making
> a rule that nobody should call printk() with zone->lock held?

If you are to remove the CONFIG_DEBUG_VM printk then I am all for it. I
am still not convinced that fiddling with dump_page in the isolation
code is justified though.

-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2019-10-10 14:18 UTC|newest]

Thread overview: 97+ 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 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 12:11         ` Qian Cai
2019-10-07 12:43         ` Michal Hocko
2019-10-07 13:07           ` Qian Cai
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 16:08             ` Qian Cai
2019-10-08 18:35             ` Michal Hocko
2019-10-08 19:06               ` Qian Cai
2019-10-08 19:06                 ` Qian Cai
2019-10-08 19:17                 ` Michal Hocko
2019-10-08 19:35                   ` Qian Cai
2019-10-08 19:35                     ` Qian Cai
2019-10-09 11:49                     ` Petr Mladek
2019-10-09 13:06                       ` Qian Cai
2019-10-09 13:06                         ` Qian Cai
2019-10-09 13:27                         ` Michal Hocko
2019-10-09 13:43                           ` Qian Cai
2019-10-09 13:43                             ` Qian Cai
2019-10-09 13:51                             ` Michal Hocko
2019-10-09 14:19                               ` Qian Cai
2019-10-09 14:19                                 ` Qian Cai
2019-10-09 14:34                                 ` Michal Hocko
2019-10-09 15:08                                   ` Qian Cai
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 13:11                                             ` Qian Cai
2019-10-10 14:18                                             ` Michal Hocko [this message]
2019-10-10 14:47                                               ` Qian Cai
2019-10-10 14:47                                                 ` Qian Cai
2019-10-10 17:30                                                 ` Michal Hocko
2019-10-10 17:48                                                   ` Qian Cai
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
2019-10-09 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
2019-10-09 15:25                 ` Qian Cai
2019-10-07 14:59   ` Qian Cai
2019-10-07 14:59     ` Qian Cai
2019-10-07 15:12     ` Michal Hocko
2019-10-07 15:33       ` Qian Cai
2019-10-07 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 13:23               ` 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 14:03                   ` 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 13:06                     ` Qian Cai
2019-10-08 13:37                     ` Michal Hocko
2019-10-08 13:08     ` Petr Mladek
2019-10-08 13:33       ` Qian Cai
2019-10-08 13:33         ` Qian Cai

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