From: Matthew Wilcox <willy@infradead.org>
To: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>, Yue Zhao <findns94@gmail.com>,
linux-mm@kvack.org, akpm@linux-foundation.org,
hannes@cmpxchg.org, mhocko@kernel.org, muchun.song@linux.dev,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: change memcg->oom_group access with atomic operations
Date: Tue, 21 Feb 2023 18:18:03 +0000 [thread overview]
Message-ID: <Y/UK2zRi+WNGrWEs@casper.infradead.org> (raw)
In-Reply-To: <Y/UDmc3+uIErpanS@P9FQF9L96D.corp.robot.car>
On Tue, Feb 21, 2023 at 09:47:05AM -0800, Roman Gushchin wrote:
> > Wouldn't a compiler be within its rights to implement a one byte store as:
> >
> > load-word
> > modify-byte-in-word
> > store-word
> >
> > and if this is a lockless store to a word which has an adjacent byte also
> > being modified by another CPU, one of those CPUs can lose its store?
> > And WRITE_ONCE would prevent the compiler from implementing the store
> > in that way.
>
> Even then it's not an issue in this case, as we end up with either 0 or 1,
> I don't see how we can screw things up here.
Thread 1:
load word containing oom_group and oom_lock
Thread 2:
store to oom_lock
Thread 1:
store word containing oom_group and oom_lock
Thread 2's store has been lost.
next prev parent reply other threads:[~2023-02-21 18:18 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-20 15:16 [PATCH] mm: change memcg->oom_group access with atomic operations Yue Zhao
2023-02-20 21:09 ` Roman Gushchin
2023-02-20 23:06 ` Shakeel Butt
2023-02-21 5:17 ` Roman Gushchin
2023-02-21 6:52 ` Shakeel Butt
2023-02-21 13:51 ` Matthew Wilcox
2023-02-21 16:56 ` Shakeel Butt
2023-02-21 18:23 ` Paul E. McKenney
2023-02-21 22:23 ` Roman Gushchin
2023-02-21 22:38 ` Paul E. McKenney
2023-02-21 23:13 ` Shakeel Butt
2023-02-21 23:38 ` Paul E. McKenney
2023-02-21 23:57 ` Roman Gushchin
2023-02-22 0:37 ` Paul E. McKenney
2023-02-22 4:28 ` Roman Gushchin
2023-02-21 17:47 ` Roman Gushchin
2023-02-21 18:15 ` Shakeel Butt
2023-02-21 18:18 ` Matthew Wilcox [this message]
2023-02-22 9:01 ` David Laight
2023-02-21 17:00 ` Martin Zhao
2023-02-21 7:22 ` Muchun Song
2023-02-21 17:48 ` Roman Gushchin
2023-02-21 17:00 ` Martin Zhao
2023-02-21 18:02 ` Roman Gushchin
2023-02-21 8:26 ` Michal Hocko
2023-02-21 17:00 ` Martin Zhao
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