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From: Tejun Heo <tj@kernel.org>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Jeff Layton <jlayton@redhat.com>,
	Steve French <sfrench@samba.org>,
	linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
	linux-pm@vger.kernel.org, linux-cifs@vger.kernel.org,
	"J. Bruce Fields" <bfields@fieldses.org>,
	Neil Brown <neilb@suse.de>
Subject: Re: [RFC PATCH] freezer: revert 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too"
Date: Mon, 31 Oct 2011 17:55:05 -0700	[thread overview]
Message-ID: <20111101005505.GO18855@google.com> (raw)
In-Reply-To: <20111031233059.GI18855@google.com>

Hey, again.

On Mon, Oct 31, 2011 at 04:30:59PM -0700, Tejun Heo wrote:
> I can't remember one off the top of my head but I'm pretty sure there
> at least are few which expect tight inter-locking between sleeps and
> wakeups.  I'll look for examples and post reply.  ISTR them being
> kernel threads so this might not apply directly but it's still a
> dangerous game to play.

Hmm... I couldn't find KILLABLE used like that but here are two
UNINTERRUPTIBLE sleep examples.

* kthread_start() depends on the fact that a kthread won't be woken up
  from UNINTERRUPTIBLE sleep spuriously.

* jfs_flush_journal() doesn't check whether the wakeup was spurious
  after waiting if !tblkGC_COMMITTED.

Maybe we can re-define KILLABLE as killable && freezable but IMHO that
requires pretty strong rationales.  If at all possible, let's not
diddle with that if it can be worked around some other way.

Thank you.

-- 
tejun

  reply	other threads:[~2011-11-01  0:55 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-10-31 22:17 Tejun Heo
2011-10-31 23:17 ` Tejun Heo
2011-10-31 23:24 ` Rafael J. Wysocki
2011-10-31 23:30   ` Tejun Heo
2011-11-01  0:55     ` Tejun Heo [this message]
2011-11-01  8:13       ` Jeff Layton
2011-11-01 10:59         ` Jeff Layton
2011-11-01 16:30           ` Tejun Heo
2011-11-01 16:49             ` Trond Myklebust
2011-11-01 16:55               ` Tejun Heo
2011-11-01 17:59             ` Oleg Nesterov
2011-11-01 18:06               ` Tejun Heo
2011-11-01 18:13                 ` Oleg Nesterov
2011-11-01 18:27                   ` Tejun Heo
2011-11-01 19:39                     ` Oleg Nesterov
2011-11-01 19:46                       ` Oleg Nesterov
2011-11-01 21:57                         ` Tejun Heo
2011-11-02 11:42                           ` Jeff Layton
2011-11-02 15:13                             ` Oleg Nesterov
2011-11-02 16:23                           ` Oleg Nesterov
2011-11-02 23:11                             ` Rafael J. Wysocki
2011-11-03 11:15                               ` Jeff Layton
2011-11-03 15:10                               ` Oleg Nesterov
2011-11-02 17:53                           ` [PATCH] wait_event_freezekillable: use freezer_do_not_count/freezer_count Oleg Nesterov
2011-11-03 10:42                             ` Jeff Layton
2011-11-03 14:13                               ` Tejun Heo
2011-11-03 15:27                                 ` Jeff Layton
2011-11-03 15:30                                   ` Tejun Heo
2011-11-01 18:26                 ` [RFC PATCH] freezer: revert 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too" Jeff Layton
2011-10-31 23:45   ` Steve French
2011-10-31 23:53     ` Tejun Heo
2011-11-01  0:02       ` Steve French
2011-11-01 17:50 ` Oleg Nesterov

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