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From: Thomas Gleixner <tglx@linutronix.de>
To: paulmck@kernel.org, Peter Zijlstra <peterz@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>,
	Uladzislau Rezki <urezki@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>, RCU <rcu@vger.kernel.org>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Matthew Wilcox <willy@infradead.org>,
	"Theodore Y . Ts'o" <tytso@mit.edu>,
	Joel Fernandes <joel@joelfernandes.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Subject: Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag
Date: Fri, 14 Aug 2020 21:33:47 +0200	[thread overview]
Message-ID: <875z9lkoo4.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200814180224.GQ4295@paulmck-ThinkPad-P72>

On Fri, Aug 14 2020 at 11:02, Paul E. McKenney wrote:
> On Fri, Aug 14, 2020 at 07:49:24PM +0200, Peter Zijlstra wrote:
>> On Fri, Aug 14, 2020 at 09:11:06AM -0700, Paul E. McKenney wrote:
>> > Just to make sure we are talking about the same thing, please see below
>> > for an untested patch that illustrates how I was interpreting your words.
>> > Was this what you had in mind?
>> 
>> No, definitely not.
>> 
>> Also, since we used to be able to use call_rcu() _everywhere_, including
>> under zone->lock, how's that working with you calling the
>> page-allocating from it?
>
> Indeed, that is exactly the problem we are trying to solve.

Wait a moment. Why are we discussing RT induced raw non raw lock
ordering at all?

Whatever kernel you variant you look at this is not working:

  lock(zone)  call_rcu() lock(zone)

It's a simple recursive dead lock, nothing else.

And that enforces the GFP_NOLOCK allocation mode or some other solution
unless you make a new rule that calling call_rcu() is forbidden while
holding zone lock or any other lock which might be nested inside the
GFP_NOWAIT zone::lock held region.

Thanks,

        tglx





  reply	other threads:[~2020-08-14 19:33 UTC|newest]

Thread overview: 111+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-09 20:43 [RFC-PATCH 0/2] __GFP_NO_LOCKS Uladzislau Rezki (Sony)
2020-08-09 20:43 ` [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag Uladzislau Rezki (Sony)
2020-08-10 12:31   ` Michal Hocko
2020-08-10 16:07     ` Uladzislau Rezki
2020-08-10 19:25       ` Michal Hocko
2020-08-11  8:19         ` Michal Hocko
2020-08-11  9:37           ` Uladzislau Rezki
2020-08-11  9:42             ` Uladzislau Rezki
2020-08-11 10:28               ` Michal Hocko
2020-08-11 10:45                 ` Uladzislau Rezki
2020-08-11 10:26             ` Michal Hocko
2020-08-11 11:33               ` Uladzislau Rezki
2020-08-11  9:18         ` Uladzislau Rezki
2020-08-11 10:21           ` Michal Hocko
2020-08-11 11:10             ` Uladzislau Rezki
2020-08-11 14:44         ` Thomas Gleixner
2020-08-11 15:22           ` Thomas Gleixner
2020-08-12 11:38             ` Thomas Gleixner
2020-08-12 12:01               ` Uladzislau Rezki
2020-08-13  7:18               ` Michal Hocko
2020-08-11 15:33           ` Paul E. McKenney
2020-08-11 15:43             ` Thomas Gleixner
2020-08-11 15:56               ` Sebastian Andrzej Siewior
2020-08-11 16:02               ` Paul E. McKenney
2020-08-11 16:19                 ` Paul E. McKenney
2020-08-11 19:39               ` Thomas Gleixner
2020-08-11 21:09                 ` Paul E. McKenney
2020-08-12  0:13                   ` Thomas Gleixner
2020-08-12  4:29                     ` Paul E. McKenney
2020-08-12  8:32                       ` Thomas Gleixner
2020-08-12 13:30                         ` Paul E. McKenney
2020-08-13  7:50                     ` Michal Hocko
2020-08-13  9:58                       ` Uladzislau Rezki
2020-08-13 11:15                         ` Michal Hocko
2020-08-13 13:27                           ` Thomas Gleixner
2020-08-13 13:45                             ` Michal Hocko
2020-08-13 14:32                             ` Matthew Wilcox
2020-08-13 16:14                               ` Thomas Gleixner
2020-08-13 16:22                                 ` Matthew Wilcox
2020-08-13 13:22                         ` Thomas Gleixner
2020-08-13 13:33                           ` Michal Hocko
2020-08-13 14:34                             ` Thomas Gleixner
2020-08-13 14:53                               ` Michal Hocko
2020-08-13 15:41                                 ` Paul E. McKenney
2020-08-13 15:54                                   ` Michal Hocko
2020-08-13 16:04                                     ` Paul E. McKenney
2020-08-13 16:13                                       ` Michal Hocko
2020-08-13 16:29                                         ` Paul E. McKenney
2020-08-13 17:12                                           ` Michal Hocko
2020-08-13 17:27                                             ` Paul E. McKenney
2020-08-13 18:31                                           ` peterz
2020-08-13 19:13                                             ` Michal Hocko
2020-08-13 16:20                                     ` Uladzislau Rezki
2020-08-13 16:36                                       ` Michal Hocko
2020-08-14 11:54                                         ` Uladzislau Rezki
2020-08-13 17:09                                 ` Thomas Gleixner
2020-08-13 17:22                                   ` Michal Hocko
2020-08-14  7:17                                   ` Michal Hocko
2020-08-14 12:15                                     ` Uladzislau Rezki
2020-08-14 12:48                                       ` Michal Hocko
2020-08-14 13:34                                         ` Paul E. McKenney
2020-08-14 14:06                                           ` Michal Hocko
2020-08-14 18:01                                             ` Paul E. McKenney
2020-08-14 23:14                                               ` Thomas Gleixner
2020-08-14 23:41                                                 ` Paul E. McKenney
2020-08-15  0:43                                                   ` Thomas Gleixner
2020-08-15  3:01                                                     ` Paul E. McKenney
2020-08-15  8:27                                                 ` Peter Zijlstra
2020-08-15 13:03                                                   ` Paul E. McKenney
2020-08-15  8:42                                                 ` Peter Zijlstra
2020-08-15 14:18                                                   ` Paul E. McKenney
2020-08-15 14:23                                                     ` Paul E. McKenney
2020-08-17  8:47                                                 ` Michal Hocko
2020-08-13 18:26                               ` peterz
2020-08-13 18:52                                 ` Paul E. McKenney
2020-08-13 22:06                                   ` peterz
2020-08-13 23:23                                     ` Paul E. McKenney
2020-08-13 23:59                                     ` Thomas Gleixner
2020-08-14  8:30                                       ` Peter Zijlstra
2020-08-14 10:23                                         ` peterz
2020-08-14 15:26                                           ` Paul E. McKenney
2020-08-14 14:14                                         ` Paul E. McKenney
2020-08-14 16:11                                           ` Paul E. McKenney
2020-08-14 17:49                                             ` Peter Zijlstra
2020-08-14 18:02                                               ` Paul E. McKenney
2020-08-14 19:33                                                 ` Thomas Gleixner [this message]
2020-08-14 20:41                                                   ` Paul E. McKenney
2020-08-14 21:52                                                     ` Peter Zijlstra
2020-08-14 23:27                                                       ` Paul E. McKenney
2020-08-14 23:40                                                       ` Thomas Gleixner
2020-08-16 22:56                                                       ` Uladzislau Rezki
2020-08-17  8:28                                                         ` Michal Hocko
2020-08-17 10:36                                                           ` Uladzislau Rezki
2020-08-17 22:28                                                           ` Paul E. McKenney
2020-08-18  7:43                                                             ` Michal Hocko
2020-08-18 13:53                                                               ` Paul E. McKenney
2020-08-18 14:43                                                                 ` Thomas Gleixner
2020-08-18 16:13                                                                   ` Paul E. McKenney
2020-08-18 16:55                                                                     ` Thomas Gleixner
2020-08-18 17:13                                                                       ` Paul E. McKenney
2020-08-18 23:26                                                                         ` Thomas Gleixner
2020-08-19 23:07                                                                           ` Paul E. McKenney
2020-08-18 15:02                                                                 ` Michal Hocko
2020-08-18 15:45                                                                   ` Uladzislau Rezki
2020-08-18 16:18                                                                   ` Paul E. McKenney
2020-08-14 16:19                                           ` peterz
2020-08-14 18:15                                             ` Paul E. McKenney
2020-08-13 13:29                         ` Uladzislau Rezki
2020-08-13 13:41                           ` Michal Hocko
2020-08-13 14:22                             ` Uladzislau Rezki
2020-08-09 20:43 ` [PATCH 2/2] rcu/tree: use " Uladzislau Rezki (Sony)

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