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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
	Anton Blanchard <anton@samba.org>, Andrew Morton <akpm@osdl.org>,
	Pavel Machek <pavel@ucw.cz>, LKML <linux-kernel@vger.kernel.org>,
	Aneesh Kumar <aneesh.kumar@gmail.com>,
	Srivatsa Vaddagiri <vatsa@in.ibm.com>,
	Gautham R Shenoy <ego@in.ibm.com>
Subject: Re: [PATCH -mm 3/7] Freezer: Remove PF_NOFREEZE from rcutorture thread
Date: Fri, 2 Mar 2007 16:58:43 -0800	[thread overview]
Message-ID: <20070303005843.GG2373@linux.vnet.ibm.com> (raw)
In-Reply-To: <20070302233337.GA267@tv-sign.ru>

On Sat, Mar 03, 2007 at 02:33:37AM +0300, Oleg Nesterov wrote:
> On 03/02, Paul E. McKenney wrote:
> >
> > One way to embed try_to_freeze() into kthread_should_stop() might be
> > as follows:
> > 
> > 	int kthread_should_stop(void)
> > 	{
> > 		if (kthread_stop_info.k == current)
> > 			return 1;
> > 		try_to_freeze();
> > 		return 0;
> > 	}
> 
> I think this is dangerous. For example, worker_thread() will probably
> need some special actions after return from refrigerator. Also, a kernel
> thread may check kthread_should_stop() in the place where try_to_freeze()
> is not safe.
> 
> Perhaps we should introduce a new helper which does this.

Good point -- the return value from try_to_freeze() is lost if one uses
the above approach.  About one third of the calls to try_to_freeze()
in 2.6.20 pay attention to the return value.

One approach would be to have a kthread_should_stop_nofreeze() for those
cases, and let the default be to try to freeze.

Is this what you had in mind?

							Thanx, Paul

  reply	other threads:[~2007-03-03  0:58 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-26  7:00 [PATCH -mm 0/6] Freezer changes Rafael J. Wysocki
2007-02-26  7:02 ` [PATCH -mm 1/6] Freezer: Read PF_BORROWED_MM in a nonracy way Rafael J. Wysocki
2007-02-26  7:05 ` [PATCH -mm 2/6] Freezer: Fix memory ordering in refrigerator Rafael J. Wysocki
2007-02-26 11:32   ` Oleg Nesterov
2007-02-26  7:06 ` [PATCH -mm 3/6] Freezer: Close theoretical race between refrigerator and thaw_tasks Rafael J. Wysocki
2007-02-26  7:08 ` [PATCH -mm 4/6] Freezer: Remove PF_NOFREEZE from rcutorture thread Rafael J. Wysocki
2007-02-26  7:11 ` [PATCH -mm 5/6] Freezer: Remove PF_NOFREEZE from bluetooth threads Rafael J. Wysocki
2007-02-26  7:13 ` [PATCH -mm 6/6] Freezer: Add try_to_freeze calls to all kernel threads Rafael J. Wysocki
2007-03-01 15:05 ` [PATCH -mm 0/7] Freezer changes (take 2) Rafael J. Wysocki
2007-03-01 15:06   ` [PATCH -mm 1/7] Freezer: Read PF_BORROWED_MM in a nonracy way Rafael J. Wysocki
2007-03-01 15:08   ` [PATCH -mm 2/7] Freezer: Close theoretical race between refrigerator and thaw_tasks Rafael J. Wysocki
2007-03-01 16:39     ` Pavel Machek
2007-03-01 15:09   ` [PATCH -mm 3/7] Freezer: Remove PF_NOFREEZE from rcutorture thread Rafael J. Wysocki
2007-03-01 19:38     ` Anton Blanchard
2007-03-01 19:54       ` Rafael J. Wysocki
2007-03-02 21:35         ` Paul E. McKenney
2007-03-02 22:16           ` Anton Blanchard
2007-03-02 23:33           ` Oleg Nesterov
2007-03-03  0:58             ` Paul E. McKenney [this message]
2007-03-03 17:32               ` Oleg Nesterov
2007-03-04  4:34                 ` Srivatsa Vaddagiri
2007-03-11 17:49                 ` [PATCH] kthread_should_stop_check_freeze (was: Re: [PATCH -mm 3/7] Freezer: Remove PF_NOFREEZE from rcutorture thread) Rafael J. Wysocki
2007-03-12  4:38                   ` Paul E. McKenney
2007-03-12  8:14                     ` Pavel Machek
2007-03-12 11:19                       ` Rafael J. Wysocki
2007-03-12 12:23                         ` Oleg Nesterov
2007-03-12 13:24                           ` [PATCH] kthread_should_stop_check_freeze Cedric Le Goater
2007-03-12 18:25                             ` Rafael J. Wysocki
2007-03-12 22:39                         ` [PATCH] kthread_should_stop_check_freeze (was: Re: [PATCH -mm 3/7] Freezer: Remove PF_NOFREEZE from rcutorture thread) Pavel Machek
2007-03-12 22:45                           ` Anton Blanchard
2007-03-13  3:14                             ` Srivatsa Vaddagiri
2007-03-13  9:16                               ` Christoph Hellwig
2007-03-13  9:58                                 ` Srivatsa Vaddagiri
2007-03-13 10:20                                   ` Christoph Hellwig
2007-03-20 18:08                             ` Pavel Machek
2007-03-13  0:58                           ` Paul E. McKenney
2007-03-20 18:10                             ` Pavel Machek
2007-03-13  5:27                   ` Gautham R Shenoy
2007-03-13  5:42                     ` Srivatsa Vaddagiri
2007-03-03  1:03             ` [PATCH -mm 3/7] Freezer: Remove PF_NOFREEZE from rcutorture thread Rafael J. Wysocki
2007-03-02  6:57     ` Gautham R Shenoy
2007-03-02 21:46       ` Paul E. McKenney
2007-03-01 15:10   ` [PATCH -mm 4/7] Freezer: Remove PF_NOFREEZE from bluetooth threads Rafael J. Wysocki
2007-03-01 15:12   ` [PATCH -mm 5/7] Freezer: Add try_to_freeze calls to all kernel threads Rafael J. Wysocki
2007-03-01 15:15   ` [PATCH -mm 6/7] Freezer: Fix vfork problem Rafael J. Wysocki
2007-03-01 15:17   ` [PATCH -mm 7/7] Freezer: Take kernel_execve into consideration Rafael J. Wysocki

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