From: Oleg Nesterov <oleg@redhat.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org,
"Eric W. Biederman" <ebiederm@xmission.com>,
Russell King - ARM Linux admin <linux@armlinux.org.uk>,
Chris Metcalf <cmetcalf@ezchip.com>,
Christoph 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 12:53:49 +0200 [thread overview]
Message-ID: <20190904105348.GA24568@redhat.com> (raw)
In-Reply-To: <20190903201135.1494-1-mathieu.desnoyers@efficios.com>
On 09/03, Mathieu Desnoyers wrote:
>
> @@ -1130,6 +1130,10 @@ struct task_struct {
> unsigned long numa_pages_migrated;
> #endif /* CONFIG_NUMA_BALANCING */
>
> +#ifdef CONFIG_MEMBARRIER
> + atomic_t membarrier_state;
> +#endif
...
> +static inline void membarrier_prepare_task_switch(struct task_struct *t)
> +{
> + if (!t->mm)
> + return;
> + atomic_set(&t->membarrier_state,
> + atomic_read(&t->mm->membarrier_state));
> +}
Why not
rq->membarrier_state = next->mm ? t->mm->membarrier_state : 0;
and
if (cpu_rq(cpu)->membarrier_state & MEMBARRIER_STATE_GLOBAL_EXPEDITED) {
...
}
in membarrier_global_expedited() ? (I removed atomic_ to simplify)
IOW, why this new member has to live in task_struct, not in rq?
Oleg.
next prev parent reply other threads:[~2019-09-04 10:53 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
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 [this message]
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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