From: Andrew Morton <akpm@linux-foundation.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: apw@canonical.com, arjan@linux.intel.com, fhrbata@redhat.com,
john.johansen@canonical.com, penguin-kernel@I-love.SAKURA.ne.jp,
rientjes@google.com, rusty@rustcorp.com.au, tj@kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] vfork: make it killable
Date: Thu, 16 Feb 2012 16:39:48 -0800 [thread overview]
Message-ID: <20120216163948.f2989a2b.akpm@linux-foundation.org> (raw)
In-Reply-To: <20120216172706.GC30393@redhat.com>
On Thu, 16 Feb 2012 18:27:06 +0100
Oleg Nesterov <oleg@redhat.com> wrote:
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -669,10 +669,34 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
>
> void complete_vfork_done(struct task_struct *tsk)
> {
> - struct completion *vfork_done = tsk->vfork_done;
> + struct completion *vfork;
>
> - tsk->vfork_done = NULL;
> - complete(vfork_done);
> + task_lock(tsk);
> + vfork = tsk->vfork_done;
> + if (likely(vfork)) {
> + tsk->vfork_done = NULL;
> + complete(vfork);
> + }
> + task_unlock(tsk);
> +}
OK, so now we don't need to test tsk->vfork_done in callers. But
mm_release() still does this, and it does it outside locks. Mistake,
or micro-optimisation? If the latter, why is the lockless peek
race-free?
next prev parent reply other threads:[~2012-02-17 0:39 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-14 16:47 [PATCH 0/6] make request_module() killable Oleg Nesterov
2012-02-14 16:47 ` [PATCH 1/6] usermodehelper: introduce umh_complete(sub_info) Oleg Nesterov
2012-02-14 16:48 ` [PATCH 2/6] usermodehelper: implement UMH_KILLABLE Oleg Nesterov
2012-02-14 16:48 ` [PATCH 3/6] usermodehelper: kill umh_wait, renumber UMH_* constants Oleg Nesterov
2012-02-15 1:09 ` Rusty Russell
2012-02-15 18:12 ` Oleg Nesterov
2012-02-14 16:48 ` [PATCH 4/6] usermodehelper: ____call_usermodehelper() doesn't need do_exit() Oleg Nesterov
2012-02-14 16:48 ` [PATCH 5/6] kmod: introduce call_modprobe() helper Oleg Nesterov
2012-02-14 16:49 ` [PATCH 6/6] kmod: make __request_module() killable Oleg Nesterov
2012-02-15 20:30 ` Andrew Morton
2012-02-16 15:04 ` Oleg Nesterov
2012-02-16 17:26 ` [PATCH 0/4] make vfork() killable Oleg Nesterov
2012-02-16 17:26 ` [PATCH 1/4] introduce complete_vfork_done() Oleg Nesterov
2012-02-17 0:35 ` Andrew Morton
2012-02-17 14:37 ` Oleg Nesterov
2012-02-16 17:27 ` [PATCH 2/4] vfork: make it killable Oleg Nesterov
2012-02-17 0:39 ` Andrew Morton [this message]
2012-02-17 14:44 ` Oleg Nesterov
2012-02-16 17:27 ` [PATCH 3/4] coredump_wait: don't call complete_vfork_done() Oleg Nesterov
2012-02-16 17:27 ` [PATCH 4/4] kill PF_STARTING Oleg Nesterov
2012-02-17 0:26 ` [PATCH 0/4] make vfork() killable Andrew Morton
2012-02-17 2:45 ` Stephen Rothwell
2012-02-17 14:46 ` Oleg Nesterov
[not found] ` <20120216173233.GF30393@redhat.com>
[not found] ` <201202172211.CGH81726.OStOJFLFHQVMFO@I-love.SAKURA.ne.jp>
[not found] ` <20120217150726.GD22440@redhat.com>
2012-02-17 18:00 ` [PATCH 0/1] hung_task: fix the broken rcu_lock_break() logic Oleg Nesterov
2012-02-17 18:00 ` [PATCH 1/1] " Oleg Nesterov
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