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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20150812133109.GA8266@redhat.com \
--to=oleg@redhat.com \
--cc=1vier1@web.de \
--cc=akpm@linux-foundation.org \
--cc=jpoimboe@redhat.com \
--cc=ktkhai@parallels.com \
--cc=linux-kernel@vger.kernel.org \
--cc=manfred@colorfullife.com \
--cc=mingo@redhat.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.