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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Michal Hocko <mhocko@kernel.org>, David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] mm, oom: prevent soft lockup on memcg oom for UP systems
Date: Mon, 16 Mar 2020 19:04:44 +0900	[thread overview]
Message-ID: <3be371a0-5b1e-7115-8659-186612ad5fb0@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20200316093152.GE11482@dhcp22.suse.cz>

On 2020/03/16 18:31, Michal Hocko wrote:
>> What happens if the allocator has SCHED_FIFO?
> 
> The same thing as a SCHED_FIFO running in a tight loop in the userspace.
> 
> As long as a high priority context depends on a resource held by a low
> priority task then we have a priority inversion problem and the page
> allocator is no real exception here. But I do not see the allocator
> is much different from any other code in the kernel. We do not add
> random sleeps here and there to push a high priority FIFO or RT tasks
> out of the execution context. We do cond_resched to help !PREEMPT
> kernels but priority related issues are really out of scope of that
> facility.
> 

Spinning with realtime priority in userspace is a userspace's bug.
Spinning with realtime priority in kernelspace until watchdog fires is
a kernel's bug. We are not responsible for userspace's bug, and I'm
asking whether the memory allocator kernel code can give enough CPU
time to other threads even if current thread has realtime priority.


  reply	other threads:[~2020-03-16 10:05 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-10 21:39 [patch] mm, oom: prevent soft lockup on memcg oom for UP systems David Rientjes
2020-03-10 22:05 ` Tetsuo Handa
2020-03-10 22:55   ` David Rientjes
2020-03-11  9:34     ` Tetsuo Handa
2020-03-11 19:38       ` David Rientjes
2020-03-11 22:04         ` Tetsuo Handa
2020-03-11 22:14           ` David Rientjes
2020-03-12  0:12             ` Tetsuo Handa
2020-03-12 18:07               ` David Rientjes
2020-03-12 22:32                 ` Andrew Morton
2020-03-16  9:31                   ` Michal Hocko
2020-03-16 10:04                     ` Tetsuo Handa [this message]
2020-03-16 10:14                       ` Michal Hocko
2020-03-13  0:15                 ` Tetsuo Handa
2020-03-13 22:01                   ` David Rientjes
2020-03-13 23:15                     ` Tetsuo Handa
2020-03-13 23:32                       ` Tetsuo Handa
2020-03-16 23:59                         ` David Rientjes
2020-03-17  3:18                           ` Tetsuo Handa
2020-03-17  4:09                             ` David Rientjes
2020-03-18  0:55                               ` [patch v2] " David Rientjes
2020-03-18  9:42                                 ` Michal Hocko
2020-03-18 21:40                                   ` David Rientjes
2020-03-18 22:03                                     ` [patch v3] " David Rientjes
2020-03-19  7:09                                       ` Michal Hocko
2020-03-12  4:23             ` [patch] " Tetsuo Handa
2020-03-10 22:10 ` Michal Hocko
2020-03-10 23:02   ` David Rientjes
2020-03-11  8:27     ` Michal Hocko
2020-03-11 19:45       ` David Rientjes
2020-03-12  8:32         ` Michal Hocko
2020-03-12 18:20           ` David Rientjes
2020-03-12 20:16             ` Michal Hocko
2020-03-16  9:32               ` Michal Hocko
2020-03-11  0:18 ` Andrew Morton
2020-03-11  0:34   ` David Rientjes
2020-03-11  8:36   ` Michal Hocko

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