From: Oleg Nesterov <oleg@redhat.com>
To: Manfred Spraul <manfred@colorfullife.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
1vier1@web.de, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Kirill Tkhai <ktkhai@parallels.com>,
Ingo Molnar <mingo@redhat.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
stable@vger.kernel.org
Subject: Re: [PATCH] ipc/sem.c: Update/correct memory barriers
Date: Wed, 12 Aug 2015 15:31:10 +0200 [thread overview]
Message-ID: <20150812133109.GA8266@redhat.com> (raw)
In-Reply-To: <1439142939-2605-1-git-send-email-manfred@colorfullife.com>
On 08/09, Manfred Spraul wrote:
>
> /*
> + * spin_unlock_wait() and !spin_is_locked() are not memory barriers, they
> + * are only control barriers.
> + * The code must pair with spin_unlock(&sem->lock) or
> + * spin_unlock(&sem_perm.lock), thus just the control barrier is insufficient.
> + *
> + * smp_rmb() is sufficient, as writes cannot pass the control barrier.
> + */
> +#define ipc_smp_acquire__after_spin_is_unlocked() smp_rmb()
Agreed.
But to remind, this can have more users. In particular, task_work_run()
which currently does mb() after spin_unlock_wait().
Can someone suggest a good "generic" name for this helper so that we can
move it into include/linux/spinlock.h?
Oleg.
next prev parent reply other threads:[~2015-08-12 13:33 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-09 17:55 [PATCH] ipc/sem.c: Update/correct memory barriers Manfred Spraul
2015-08-10 8:15 ` Peter Zijlstra
2015-08-12 13:31 ` Oleg Nesterov [this message]
-- strict thread matches above, loose matches on Subject: below --
2015-03-01 16:18 Manfred Spraul
2015-03-01 19:16 ` Oleg Nesterov
2015-02-28 20:36 Manfred Spraul
2015-02-28 21:45 ` Peter Zijlstra
2015-02-28 23:34 ` Paul E. McKenney
2015-03-01 13:28 ` Oleg Nesterov
2015-03-01 13:22 ` Oleg Nesterov
2015-03-01 16:07 ` Manfred Spraul
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