From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Will Deacon <will@kernel.org>, paulmck <paulmck@kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
Andy Lutomirski <luto@amacapital.net>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Alan Stern <stern@rowland.harvard.edu>,
linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH 1/3] sched: fix exit_mm vs membarrier (v4)
Date: Tue, 20 Oct 2020 10:59:58 -0400 (EDT) [thread overview]
Message-ID: <1123875792.30589.1603205998119.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20201020143648.GU2628@hirez.programming.kicks-ass.net>
----- On Oct 20, 2020, at 10:36 AM, Peter Zijlstra peterz@infradead.org wrote:
> On Tue, Oct 20, 2020 at 09:47:13AM -0400, Mathieu Desnoyers wrote:
>> +void membarrier_update_current_mm(struct mm_struct *next_mm)
>> +{
>> + struct rq *rq = this_rq();
>> + int membarrier_state = 0;
>> +
>> + if (next_mm)
>> + membarrier_state = atomic_read(&next_mm->membarrier_state);
>> + if (READ_ONCE(rq->membarrier_state) == membarrier_state)
>> + return;
>> + WRITE_ONCE(rq->membarrier_state, membarrier_state);
>> +}
>
> This is suspisioucly similar to membarrier_switch_mm().
>
> Would something like so make sense?
Very much yes. Do you want me to re-send the series, or you
want to fold this in as you merge it ?
Thanks,
Mathieu
>
> ---
> --- a/kernel/sched/membarrier.c
> +++ b/kernel/sched/membarrier.c
> @@ -206,14 +206,7 @@ void membarrier_exec_mmap(struct mm_stru
>
> void membarrier_update_current_mm(struct mm_struct *next_mm)
> {
> - struct rq *rq = this_rq();
> - int membarrier_state = 0;
> -
> - if (next_mm)
> - membarrier_state = atomic_read(&next_mm->membarrier_state);
> - if (READ_ONCE(rq->membarrier_state) == membarrier_state)
> - return;
> - WRITE_ONCE(rq->membarrier_state, membarrier_state);
> + membarrier_switch_mm(this_rq(), NULL, next_mm);
> }
>
> static int membarrier_global_expedited(void)
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index d2621155393c..3d589c2ffd28 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2645,12 +2645,14 @@ static inline void membarrier_switch_mm(struct rq *rq,
> struct mm_struct *prev_mm,
> struct mm_struct *next_mm)
> {
> - int membarrier_state;
> + int membarrier_state = 0;
>
> if (prev_mm == next_mm)
> return;
>
> - membarrier_state = atomic_read(&next_mm->membarrier_state);
> + if (next_mm)
> + membarrier_state = atomic_read(&next_mm->membarrier_state);
> +
> if (READ_ONCE(rq->membarrier_state) == membarrier_state)
> return;
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2020-10-20 15:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201020134715.13909-1-mathieu.desnoyers@efficios.com>
2020-10-20 13:47 ` [PATCH 1/3] sched: fix exit_mm vs membarrier (v4) Mathieu Desnoyers
2020-10-20 14:36 ` Peter Zijlstra
2020-10-20 14:59 ` Mathieu Desnoyers [this message]
2020-10-22 6:51 ` Boqun Feng
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