From: Andrew Morton <akpm@osdl.org>
To: vatsa@in.ibm.com
Cc: Oleg Nesterov <oleg@tv-sign.ru>,
David Howells <dhowells@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
Ingo Molnar <mingo@elte.hu>, Linus Torvalds <torvalds@osdl.org>,
linux-kernel@vger.kernel.org, Gautham shenoy <ego@in.ibm.com>
Subject: Re: [PATCH] flush_cpu_workqueue: don't flush an empty ->worklist
Date: Mon, 8 Jan 2007 21:26:56 -0800 [thread overview]
Message-ID: <20070108212656.ca77a3ba.akpm@osdl.org> (raw)
In-Reply-To: <20070109050417.GC589@in.ibm.com>
On Tue, 9 Jan 2007 10:34:17 +0530
Srivatsa Vaddagiri <vatsa@in.ibm.com> wrote:
> On Mon, Jan 08, 2007 at 03:54:28PM -0800, Andrew Morton wrote:
> > Furthermore I don't know which of these need to be tossed overboard if/when
> > we get around to using the task freezer for CPU hotplug synchronisation.
> > Hopefully, a lot of them. I don't really understand why we're continuing
> > to struggle with the existing approach before that question is settled.
>
> Good point!
>
> Fundamentally, I think we need to answer this question:
>
> "Do we provide *some* mechanism to block concurrent hotplug operations
> from happening? By hotplug operations I mean both changes to the bitmap
> and execution of all baclbacks in CPU_DEAD/ONLINE etc"
>
> If NO, then IMHO we will be forever fixing races
>
> If YES, then what is that mechanism? freeze_processes()? or a magical
> lock?
>
> freeze_processes() cant be that mechanism, if my understanding of it is
> correct - see http://lkml.org/lkml/2007/1/8/149
That's not correct. freeze_processes() will freeze *all* processes. All
of them are forced to enter refrigerator(). With the mysterious exception
of some I/O-related kernel threads, which might need some thought.
> and
> http://marc.theaimsgroup.com/?l=linux-kernel&m=116817460726058.
Am not sure how that's related.
> I would be happy to be corrected if the above impression of
> freeze_processes() is corrected ..
It could be that the freezer needs a bit of work for this application.
Obviously we're not interested in the handling of disk I/O, so we'd really
like to do a simple
try_to_freeze_tasks(FREEZER_USER_SPACE|FREEZER_KERNEL_THREADS), but the
code isn't set up to do that (it should be). The other non-swsusp callers
probably want this change as well. But that's all a minor matter.
next prev parent reply other threads:[~2007-01-09 5:30 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-17 22:34 [PATCH, RFC] reimplement flush_workqueue() Oleg Nesterov
2006-12-18 3:09 ` Linus Torvalds
2006-12-19 0:27 ` Andrew Morton
2006-12-19 0:43 ` Oleg Nesterov
2006-12-19 1:00 ` Andrew Morton
2007-01-04 11:32 ` Srivatsa Vaddagiri
2007-01-04 14:29 ` Oleg Nesterov
2007-01-04 15:56 ` Srivatsa Vaddagiri
2007-01-04 16:31 ` Oleg Nesterov
2007-01-04 16:57 ` Srivatsa Vaddagiri
2007-01-04 17:18 ` Andrew Morton
2007-01-04 18:09 ` Oleg Nesterov
2007-01-04 18:31 ` Andrew Morton
2007-01-05 9:03 ` Srivatsa Vaddagiri
2007-01-05 14:07 ` Oleg Nesterov
2007-01-06 15:24 ` Srivatsa Vaddagiri
2007-01-05 8:56 ` Srivatsa Vaddagiri
2007-01-05 12:42 ` Oleg Nesterov
2007-01-06 15:11 ` Srivatsa Vaddagiri
2007-01-06 15:10 ` [PATCH] fix-flush_workqueue-vs-cpu_dead-race-update Oleg Nesterov
2007-01-06 15:45 ` Srivatsa Vaddagiri
2007-01-06 16:30 ` Oleg Nesterov
2007-01-06 16:38 ` Srivatsa Vaddagiri
2007-01-06 17:34 ` Oleg Nesterov
2007-01-07 10:43 ` Srivatsa Vaddagiri
2007-01-07 12:56 ` Oleg Nesterov
2007-01-07 14:22 ` Oleg Nesterov
2007-01-07 14:42 ` Oleg Nesterov
2007-01-07 16:43 ` Srivatsa Vaddagiri
2007-01-07 17:01 ` Srivatsa Vaddagiri
2007-01-07 17:33 ` Oleg Nesterov
2007-01-07 17:18 ` Oleg Nesterov
2007-01-07 16:21 ` Srivatsa Vaddagiri
2007-01-07 17:09 ` Oleg Nesterov
2007-01-06 19:11 ` Andrew Morton
2007-01-06 19:13 ` Ingo Molnar
2007-01-07 11:00 ` Srivatsa Vaddagiri
2007-01-07 19:59 ` Andrew Morton
2007-01-07 21:01 ` [PATCH] flush_cpu_workqueue: don't flush an empty ->worklist Oleg Nesterov
2007-01-08 23:54 ` Andrew Morton
2007-01-09 5:04 ` Srivatsa Vaddagiri
2007-01-09 5:26 ` Andrew Morton [this message]
2007-01-09 6:56 ` Ingo Molnar
2007-01-09 9:33 ` Srivatsa Vaddagiri
2007-01-09 9:44 ` Ingo Molnar
2007-01-09 9:51 ` Andrew Morton
2007-01-09 10:09 ` Srivatsa Vaddagiri
2007-01-09 10:15 ` Andrew Morton
2007-01-09 15:07 ` Oleg Nesterov
2007-01-09 15:59 ` Srivatsa Vaddagiri
2007-01-09 16:38 ` Oleg Nesterov
2007-01-09 16:46 ` Srivatsa Vaddagiri
2007-01-09 16:56 ` Oleg Nesterov
2007-01-14 23:54 ` Oleg Nesterov
2007-01-15 4:33 ` Srivatsa Vaddagiri
2007-01-15 12:54 ` Oleg Nesterov
2007-01-15 13:08 ` Oleg Nesterov
2007-01-15 16:18 ` Srivatsa Vaddagiri
2007-01-15 16:55 ` Oleg Nesterov
2007-01-16 5:26 ` Srivatsa Vaddagiri
2007-01-16 13:27 ` Oleg Nesterov
2007-01-17 6:17 ` Srivatsa Vaddagiri
2007-01-17 15:47 ` Oleg Nesterov
2007-01-17 16:12 ` Srivatsa Vaddagiri
2007-01-17 17:01 ` Oleg Nesterov
2007-01-17 16:25 ` Srivatsa Vaddagiri
2007-01-07 21:51 ` [PATCH] fix-flush_workqueue-vs-cpu_dead-race-update Oleg Nesterov
2007-01-08 15:22 ` Srivatsa Vaddagiri
2007-01-08 15:56 ` Oleg Nesterov
2007-01-08 16:31 ` Srivatsa Vaddagiri
2007-01-08 17:06 ` Oleg Nesterov
2007-01-08 18:37 ` Pallipadi, Venkatesh
2007-01-09 1:11 ` Srivatsa Vaddagiri
2007-01-09 4:39 ` Srivatsa Vaddagiri
2007-01-09 14:38 ` Oleg Nesterov
2007-01-08 15:37 ` Srivatsa Vaddagiri
2007-01-04 12:02 ` [PATCH, RFC] reimplement flush_workqueue() Srivatsa Vaddagiri
2007-01-04 14:38 ` Oleg Nesterov
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