From: Oleg Nesterov <oleg@tv-sign.ru>
To: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>,
akpm@osdl.org, paulmck@us.ibm.com, mingo@elte.hu,
dipankar@in.ibm.com, venkatesh.pallipadi@intel.com,
linux-kernel@vger.kernel.org, rjw@sisk.pl
Subject: Re: [RFC PATCH(Experimental) 1/4] freezer-cpu-hotplug core
Date: Fri, 16 Feb 2007 19:06:40 +0300 [thread overview]
Message-ID: <20070216160640.GD83@tv-sign.ru> (raw)
In-Reply-To: <20070216071617.GB4527@in.ibm.com>
On 02/16, Srivatsa Vaddagiri wrote:
>
> On Wed, Feb 14, 2007 at 11:22:09PM +0300, Oleg Nesterov wrote:
> > > o Splits CPU_DEAD into two events namely
> > > - CPU_DEAD: which will be handled while the processes are still
> > > frozen.
> > >
> > > - CPU_DEAD_KILL_THREADS: To be handled after we thaw_processes.
> >
> >
> > Imho, this is not right. This change the meaning of CPU_DEAD, and so
> > we should fix all users of CPU_DEAD as well.
>
> Why should we fix all users? Only users who were doing a kthread_stop()
> in CPU_DEAD need to be fixed. From my count, only 5 users (out of a
> total of 35) need to be fixed to not do kthread_stop in CPU_DEAD.
But still we need to fix or at least check them,
> > How about
> >
> > CPU_DEAD_WHATEVER
> > the processes are still frozen
> >
> > CPU_DEAD
> > after we thaw_processes
> >
> > This way we can add processing of the new CPU_DEAD_WHATEVER event where
> > it may help.
>
> Well, -most- of the work needs to be done in a state when processes are
> frozen. The only exception is cleaning up of per-cpu threads (which is
> not possible with processes frozen - if we can find a way to make that
> possible, then everything can be done in CPU_DEAD).
>
> If we go by the change suggested above, then we need to fix all users of
> CPU_DEAD
Sorry, I can't understand you.
This patch adds the new state, why should we fix all users of CPU_DEAD
if they were correct? CPU_DEAD retains its old meaning, all users should
work as before?
> to do what they are doing in CPU_DEAD_WHATEVER (when processes
> are frozen).
We don't have such users! because we don't have CPU_DEAD_WHATEVER yet.
IOW: I think this new state should have a new name, CPU_DEAD should continue
to be called as a last step. Then we can teach cpu callback's to to take an
advantage of CPU_DEAD_WHATEVER, and we can do this in a separate patches.
No?
> > CPU_UP_PREPARE is called after freeze_processes()... Probably this works,
> > but imho this is no good. Suppose for a moment that khelper will be frozen
> > (yes, yes it can't be), then we can't do kthread_create().
>
> Yes, I am worried about doing so many things with processes frozen.
> Maybe time (and more testing) will tell us if this is a bad thing or
> not. The only dependency I have found so far is that kthread workqueue needs to
> be up (and hence its worker thread needs to be exempted from hotplug
> freeze). We should mark kthread workqueue accordingly as not freezable
> for hotplug.
Yes, this is what I was talking about.
Oleg.
next prev parent reply other threads:[~2007-02-16 16:07 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-14 14:40 [RFC PATCH(Experimental) 0/4] Freezer based Cpu-hotplug Gautham R Shenoy
2007-02-14 14:42 ` [RFC PATCH(Experimental) 1/4] freezer-cpu-hotplug core Gautham R Shenoy
2007-02-14 14:43 ` [RFC PATCH(Experimental) 2/4] Revert changes to workqueue.c Gautham R Shenoy
2007-02-14 14:43 ` [RFC PATCH(Experimental) 3/4] Revert changes to sched.c and slab.c Gautham R Shenoy
2007-02-14 14:44 ` [RFC PATCH(Experimental) 4/4] Rip out lock_cpu_hotplug from linux Gautham R Shenoy
2007-02-14 14:59 ` [RFC PATCH(Experimental) 2/4] Revert changes to workqueue.c Srivatsa Vaddagiri
2007-02-14 15:24 ` Srivatsa Vaddagiri
2007-02-14 20:23 ` Oleg Nesterov
2007-02-14 20:09 ` Oleg Nesterov
2007-02-16 5:26 ` Srivatsa Vaddagiri
2007-02-16 15:33 ` Oleg Nesterov
2007-02-16 16:47 ` Srivatsa Vaddagiri
2007-02-16 18:45 ` Oleg Nesterov
2007-02-16 23:59 ` Oleg Nesterov
2007-02-17 2:29 ` Srivatsa Vaddagiri
2007-02-17 21:59 ` Oleg Nesterov
2007-02-20 15:12 ` Srivatsa Vaddagiri
2007-02-20 20:09 ` Oleg Nesterov
2007-02-21 6:29 ` Srivatsa Vaddagiri
2007-02-21 14:30 ` Oleg Nesterov
2007-02-21 14:37 ` Gautham R Shenoy
2007-02-21 15:53 ` Srivatsa Vaddagiri
2007-02-14 15:31 ` [RFC PATCH(Experimental) 1/4] freezer-cpu-hotplug core Srivatsa Vaddagiri
2007-02-14 19:47 ` Oleg Nesterov
2007-02-16 6:48 ` Srivatsa Vaddagiri
2007-02-16 15:47 ` Oleg Nesterov
2007-02-14 20:22 ` Oleg Nesterov
2007-02-16 7:16 ` Srivatsa Vaddagiri
2007-02-16 8:12 ` Srivatsa Vaddagiri
2007-02-16 9:29 ` Rafael J. Wysocki
2007-02-16 9:59 ` Srivatsa Vaddagiri
2007-02-16 11:06 ` Rafael J. Wysocki
2007-02-16 19:46 ` Oleg Nesterov
2007-02-17 2:31 ` Srivatsa Vaddagiri
2007-02-17 5:32 ` Gautham R Shenoy
2007-02-17 11:19 ` Gautham R Shenoy
2007-02-16 16:06 ` Oleg Nesterov [this message]
2007-02-14 21:43 ` [RFC PATCH(Experimental) 0/4] Freezer based Cpu-hotplug Rafael J. Wysocki
2007-02-15 6:34 ` Gautham R Shenoy
2007-02-15 8:09 ` Rafael J. Wysocki
2007-02-15 12:20 ` Gautham R Shenoy
2007-02-15 13:31 ` Rafael J. Wysocki
2007-02-15 14:25 ` Gautham R Shenoy
2007-02-17 11:24 ` Rafael J. Wysocki
2007-02-17 21:34 ` Oleg Nesterov
2007-02-17 22:24 ` Rafael J. Wysocki
2007-02-17 23:42 ` Oleg Nesterov
2007-02-17 23:47 ` Oleg Nesterov
2007-02-18 10:43 ` Rafael J. Wysocki
2007-02-18 11:31 ` Oleg Nesterov
2007-02-18 12:14 ` Rafael J. Wysocki
2007-02-18 14:52 ` freezer problems Oleg Nesterov
2007-02-18 15:14 ` Rafael J. Wysocki
2007-02-18 16:19 ` Oleg Nesterov
2007-02-18 18:14 ` Rafael J. Wysocki
2007-02-18 18:56 ` Rafael J. Wysocki
2007-02-18 22:01 ` Oleg Nesterov
2007-02-18 23:19 ` Rafael J. Wysocki
2007-02-19 20:23 ` Oleg Nesterov
2007-02-19 21:21 ` Rafael J. Wysocki
2007-02-19 22:41 ` Oleg Nesterov
2007-02-19 23:35 ` Rafael J. Wysocki
2007-02-20 0:12 ` Oleg Nesterov
2007-02-20 0:32 ` Rafael J. Wysocki
2007-02-20 0:50 ` Oleg Nesterov
2007-02-20 18:28 ` Rafael J. Wysocki
2007-02-20 18:29 ` Rafael J. Wysocki
2007-02-21 18:14 ` Paul E. McKenney
2007-02-21 18:13 ` Rafael J. Wysocki
2007-02-21 18:27 ` Paul E. McKenney
2007-02-21 20:03 ` Oleg Nesterov
2007-02-21 20:47 ` Rafael J. Wysocki
2007-02-21 21:06 ` Paul E. McKenney
2007-02-21 23:10 ` Rafael J. Wysocki
2007-02-22 10:47 ` Oleg Nesterov
2007-02-22 11:33 ` Oleg Nesterov
2007-02-22 17:03 ` Rafael J. Wysocki
2007-02-22 17:44 ` Oleg Nesterov
2007-02-22 21:56 ` Rafael J. Wysocki
2007-02-23 18:15 ` Oleg Nesterov
2007-02-23 3:02 ` Gautham R Shenoy
2007-02-18 15:09 ` [RFC PATCH(Experimental) 0/4] Freezer based Cpu-hotplug Rafael J. Wysocki
2007-02-18 16:11 ` Oleg Nesterov
2007-02-18 18:51 ` Rafael J. Wysocki
2007-02-18 10:32 ` Rafael J. Wysocki
2007-02-18 11:32 ` Oleg Nesterov
2007-02-18 12:12 ` Rafael J. Wysocki
2007-02-18 15:06 ` Oleg Nesterov
2007-02-18 12:56 ` Pavel Machek
2007-02-21 14:52 ` Gautham R Shenoy
2007-02-21 19:42 ` Pavel Machek
[not found] ` <200702231041.17136.rjw@sisk.pl>
[not found] ` <20070223100817.GA10973@in.ibm.com>
[not found] ` <200702231115.00718.rjw@sisk.pl>
[not found] ` <20070223104723.GB10973@in.ibm.com>
[not found] ` <20070223110201.GC10973@in.ibm.com>
2007-02-23 19:03 ` freezer problems Gautham R Shenoy
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