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    SubjectRe: Boot time regression in 2.6.38 after initial wq merge
    On Wed, Feb 23, 2011 at 10:38:54AM +0100, Tejun Heo wrote:
    > Hello,
    >
    > On Tue, Feb 22, 2011 at 09:20:42PM -0800, Dmitry Torokhov wrote:
    > > On Tue, Feb 22, 2011 at 09:14:46PM +0100, pantherchen@versanet.de wrote:
    > > > On 02/22/2011 08:52 PM, Dmitry Torokhov wrote:
    > > > >Ewww... tty/ldisc...
    > > > >
    > > > >Does it help if you change drivers/input/serio/serio.c::serio_queue_event()
    > > > >from calling
    > > > >
    > > > > schedule_work(&serio_event_work);
    > > > >
    > > > >to call
    > > > >
    > > > > queue_work(system_long_wq,&serio_event_work);
    > > > >
    > > > >?
    > > >
    > > > Yes, that works: http://img.xrmb2.net/images/499337.png
    > > >
    > >
    > > Great!
    > >
    > > OK, so below is properly formatted patch. I am going to send it upstream
    > > unless somebody objects.
    >
    > Ah, okay, thanks a lot for tracking this down, Dmitry. Didn't expect
    > flush_scheduled_work() to bite back this way. :-)
    >
    > > Input: serio/gameport - use 'long' system workqueue
    > >
    > > From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
    > >
    > > Commit 8ee294cd9def0004887da7f44b80563493b0a097 converted serio
    > > subsystem event handling from using a dedicated thread to using
    > > common workqueue. Unfortunately, this regressed our boot times,
    > > due to the fact that serio jobs take long time to execute. While
    > > the new concurrency managed workqueue code manages long-playing
    > > works just fine and schedules additional workers as needed, such
    > > works wreck havoc among remaining users of flush_scheduled_work().
    > >
    > > To solve this problem let's move serio/gameport works from system_wq
    > > to system_long_wq which nobody tries to flush.
    > >
    > > Reported-and-tested-by: Hernando Torque <pantherchen@versanet.de>
    > > Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
    >
    > Acked-by: Tejun Heo <tj@kernel.org>
    >
    > Most flush_scheduled_work() users are already gone and once all of
    > them are gone, system_long_wq can be removed without causing any
    > difference.

    Right. When you are ready to remove system_long_wq simply revert this
    path and all should be set.

    Thanks.

    --
    Dmitry


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