From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>, Darren Hart <darren@dvhart.com>,
Yi Wang <wang.yi59@zte.com.cn>, Yang Tao <yang.tao172@zte.com.cn>,
Oleg Nesterov <oleg@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
Carlos O'Donell <carlos@redhat.com>,
Alexander Viro <viro@zeniv.linux.org.uk>
Subject: Re: [patch 09/12] futex: Provide state handling for exec() as well
Date: Thu, 7 Nov 2019 10:54:40 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.21.1911071053400.4256@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20191107094943.GF4131@hirez.programming.kicks-ass.net>
On Thu, 7 Nov 2019, Peter Zijlstra wrote:
> On Wed, Nov 06, 2019 at 10:55:43PM +0100, Thomas Gleixner wrote:
>
> > +static void futex_cleanup_end(struct task_struct *tsk, int state)
> > +{
> > + /*
> > + * Lockless store. The only side effect is that an observer might
> > + * take another loop until it becomes visible.
> > + */
> > + tsk->futex_state = state;
>
> As I mentioned yesterday, paranoia would've made me write this as
> smp_store_release(), also to avoid it creaping back into the locked
> region.
>
> That is, the comment above deals with it being visible late, but it
> could be visible early.
>
> At the same time, if this is a release, what does it pair with. The
> obvious place would be the load in handle_exit_race() but that didn't
> want to make sense last night -- and I'm not sure it wants to make more
> sense today.
Right. I couldn't come up with any sensible argument either.
Thanks,
tglx
next prev parent reply other threads:[~2019-11-07 9:54 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 21:55 [patch 00/12] futex: Cure robust/PI futex exit races Thomas Gleixner
2019-11-06 21:55 ` [patch 01/12] futex: Prevent robust futex exit race Thomas Gleixner
2019-11-06 21:55 ` [patch 02/12] futex: Move futex exit handling into futex code Thomas Gleixner
2019-11-07 9:24 ` Peter Zijlstra
2019-11-07 9:38 ` Thomas Gleixner
2019-11-15 18:19 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-16 20:53 ` Borislav Petkov
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 03/12] futex: Replace PF_EXITPIDONE with a state Thomas Gleixner
2019-11-15 18:19 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 04/12] exit/exec: Seperate mm_release() Thomas Gleixner
2019-11-15 18:19 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 05/12] futex: Split futex_mm_release() for exit/exec Thomas Gleixner
2019-11-15 18:19 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 06/12] futex: Set task::futex state to DEAD right after handling futex exit Thomas Gleixner
2019-11-15 18:19 ` [tip: locking/core] futex: Set task::futex_state " tip-bot2 for Thomas Gleixner
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 07/12] futex: Mark the begin of futex exit explicitly Thomas Gleixner
2019-11-15 18:19 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 08/12] futex: Sanitize exit state handling Thomas Gleixner
2019-11-07 9:38 ` Peter Zijlstra
2019-11-15 18:19 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 09/12] futex: Provide state handling for exec() as well Thomas Gleixner
2019-11-07 9:49 ` Peter Zijlstra
2019-11-07 9:54 ` Thomas Gleixner [this message]
2019-11-15 18:19 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 10/12] futex: Add mutex around futex exit Thomas Gleixner
2019-11-15 18:19 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 11/12] futex: Provide distinct return value when owner is exiting Thomas Gleixner
2019-11-15 18:19 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 12/12] futex: Prevent exit livelock Thomas Gleixner
2019-11-15 18:19 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20 9:38 ` tip-bot2 for Thomas Gleixner
2019-11-07 8:29 ` [patch 00/12] futex: Cure robust/PI futex exit races Ingo Molnar
2019-11-07 8:41 ` Ingo Molnar
2019-11-07 9:40 ` Peter Zijlstra
2019-11-07 15:03 ` Oleg Nesterov
2019-11-07 22:29 ` Florian Weimer
2019-11-07 22:40 ` Florian Weimer
2019-11-08 7:38 ` Florian Weimer
2019-11-08 9:18 ` Thomas Gleixner
2019-11-08 10:17 ` Florian Weimer
2019-11-08 10:37 ` Thomas Gleixner
2019-11-08 11:51 ` Thomas Gleixner
2019-11-11 9:48 ` Florian Weimer
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