From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Jann Horn <jannh@google.com>, Jens Axboe <axboe@kernel.dk>,
io-uring <io-uring@vger.kernel.org>,
stable <stable@vger.kernel.org>, Josef <josef.grieb@gmail.com>
Subject: Re: [PATCH 2/2] io_uring: use TWA_SIGNAL for task_work if the task isn't running
Date: Tue, 11 Aug 2020 09:49:25 +0200 [thread overview]
Message-ID: <20200811074925.GT3982@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20200811072637.GC21797@redhat.com>
On Tue, Aug 11, 2020 at 09:26:37AM +0200, Oleg Nesterov wrote:
> On 08/11, Oleg Nesterov wrote:
> >
> > On 08/11, Peter Zijlstra wrote:
> > >
> > > On Tue, Aug 11, 2020 at 08:45:16AM +0200, Oleg Nesterov wrote:
> > > >
> > > > ->jobctl is always modified with ->siglock held, do we really need
> > > > WRITE_ONCE() ?
> > >
> > > In theory, yes. The compiler doesn't know about locks, it can tear
> > > writes whenever it feels like it.
> >
> > Yes, but why does this matter? Could you spell please?
>
> Do you mean that compiler can temporary set/clear JOBCTL_TASK_WORK
> when it sets/clears another bit?
Possibly, afaict the compiler is allowed to 'spill' intermediate state
into the variable. If any intermediate state has the bit clear,...
next prev parent reply other threads:[~2020-08-11 7:49 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-08 18:34 [PATCHSET 0/2] io_uring: use TWA_SIGNAL more carefully Jens Axboe
2020-08-08 18:34 ` [PATCH 1/2] kernel: split task_work_add() into two separate helpers Jens Axboe
2020-08-10 11:37 ` peterz
2020-08-10 15:01 ` Jens Axboe
2020-08-10 15:28 ` peterz
2020-08-10 17:51 ` Jens Axboe
2020-08-10 19:53 ` Peter Zijlstra
2020-08-08 18:34 ` [PATCH 2/2] io_uring: use TWA_SIGNAL for task_work if the task isn't running Jens Axboe
2020-08-10 11:42 ` peterz
2020-08-10 15:02 ` Jens Axboe
2020-08-10 19:21 ` Jens Axboe
2020-08-10 20:12 ` Peter Zijlstra
2020-08-10 20:13 ` Jens Axboe
2020-08-10 20:25 ` Jens Axboe
2020-08-10 20:32 ` Peter Zijlstra
2020-08-10 20:35 ` Jens Axboe
2020-08-10 20:35 ` Jann Horn
2020-08-10 21:06 ` Jens Axboe
2020-08-10 21:10 ` Peter Zijlstra
2020-08-10 21:12 ` Jens Axboe
2020-08-10 21:26 ` Jann Horn
2020-08-10 21:28 ` Jens Axboe
2020-08-10 22:01 ` Jens Axboe
2020-08-10 22:41 ` Jann Horn
2020-08-11 1:25 ` Jens Axboe
2020-08-11 6:45 ` Oleg Nesterov
2020-08-11 6:56 ` Peter Zijlstra
2020-08-11 7:14 ` Oleg Nesterov
2020-08-11 7:26 ` Oleg Nesterov
2020-08-11 7:49 ` Peter Zijlstra [this message]
2020-08-11 7:45 ` Peter Zijlstra
2020-08-11 8:10 ` Oleg Nesterov
2020-08-11 13:06 ` Jens Axboe
2020-08-11 14:05 ` Oleg Nesterov
2020-08-11 14:12 ` Jens Axboe
2020-08-10 21:27 ` Jens Axboe
2020-08-10 20:16 ` Jens Axboe
2020-08-13 16:25 ` Sasha Levin
2020-08-19 23:57 ` Sasha Levin
2020-08-19 23:59 ` Jens Axboe
2020-08-20 0:02 ` Jens Axboe
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