From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
paulmck <paulmck@linux.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"Russell King, ARM Linux" <linux@armlinux.org.uk>,
Chris Metcalf <cmetcalf@ezchip.com>, Chris Lameter <cl@linux.com>,
Kirill Tkhai <tkhai@yandex.ru>, Mike Galbraith <efault@gmx.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [RFC PATCH 1/2] Fix: sched/membarrier: p->mm->membarrier_state racy load
Date: Wed, 4 Sep 2019 14:03:37 +0200 [thread overview]
Message-ID: <20190904120336.GC24568@redhat.com> (raw)
In-Reply-To: <20190904112819.GD2349@hirez.programming.kicks-ass.net>
On 09/04, Peter Zijlstra wrote:
>
> + struct task_struct *g, *t;
> +
> + read_lock(&tasklist_lock);
> + do_each_thread(g, t) {
for_each_process_thread() looks better
> + if (t->mm == mm) {
> + atomic_or(MEMBARRIER_STATE_GLOBAL_EXPEDITED,
> + &t->membarrier_state);
> + }
then you also need to change dup_task_struct(), it should clear
->membarrier_state unless CLONE_VM.
And probably unuse_mm() should clear current->membarrier_state too.
Hmm. And it can race with copy_process() anyway, tasklist_lock can't
really help. So copy_process() needs to do
write_lock_irq(&tasklist_lock);
...
if (clone_flags & CLONE_VM)
p->membarrier_state = current->membarrier_state;
else
p->membarrier_state = 0;
Oleg.
next prev parent reply other threads:[~2019-09-04 12:03 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-03 20:11 [RFC PATCH 1/2] Fix: sched/membarrier: p->mm->membarrier_state racy load Mathieu Desnoyers
2019-09-03 20:11 ` [RFC PATCH 2/2] Fix: sched/membarrier: private expedited registration check Mathieu Desnoyers
2019-09-03 20:24 ` [RFC PATCH 1/2] Fix: sched/membarrier: p->mm->membarrier_state racy load Peter Zijlstra
2019-09-03 20:36 ` Linus Torvalds
2019-09-04 15:19 ` Mathieu Desnoyers
2019-09-04 16:09 ` Peter Zijlstra
2019-09-04 17:12 ` Mathieu Desnoyers
2019-09-04 18:26 ` Peter Zijlstra
2019-09-06 0:51 ` Mathieu Desnoyers
2019-09-03 20:41 ` Mathieu Desnoyers
2019-09-04 11:28 ` Peter Zijlstra
2019-09-04 11:49 ` Peter Zijlstra
2019-09-04 15:26 ` Mathieu Desnoyers
2019-09-04 12:03 ` Oleg Nesterov [this message]
2019-09-04 12:43 ` Peter Zijlstra
2019-09-04 13:17 ` Oleg Nesterov
2019-09-03 20:27 ` Linus Torvalds
2019-09-03 20:53 ` Mathieu Desnoyers
2019-09-04 10:53 ` Oleg Nesterov
2019-09-04 11:39 ` Peter Zijlstra
2019-09-04 15:24 ` Mathieu Desnoyers
2019-09-04 11:11 ` Oleg Nesterov
2019-09-04 16:11 ` Mathieu Desnoyers
2019-09-08 13:46 ` Mathieu Desnoyers
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