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xen: explicitly create/destroy stop_machine workqueues outside suspend/resume region.

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I have observed cases where the implicit stop_machine_destroy() done by
stop_machine() hangs while destroying the workqueues, specifically in
kthread_stop(). This seems to be because timer ticks are not restarted
until after stop_machine() returns.

Fortunately stop_machine provides a facility to pre-create/post-destroy
the workqueues so use this to ensure that workqueues are only destroyed
after everything is really up and running again.

I only actually observed this failure with 2.6.30. It seems that newer
kernels are somehow more robust against doing kthread_stop() without timer
interrupts (I tried some backports of some likely looking candidates but
did not track down the commit which added this robustness). However this
change seems like a reasonable belt&braces thing to do.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stable Kernel <stable@kernel.org>
This commit is contained in:
Ian Campbell 2009-12-01 11:47:15 +00:00 committed by Jeremy Fitzhardinge
parent 65f63384b3
commit b4606f2165
1 changed files with 11 additions and 1 deletions
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12
drivers/xen/manage.c
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@ -79,6 +79,12 @@ static void do_suspend(void)
shutting_down = SHUTDOWN_SUSPEND;
err = stop_machine_create();
if (err) {
printk(KERN_ERR "xen suspend: failed to setup stop_machine %d\n", err);
goto out;
}
#ifdef CONFIG_PREEMPT
/* If the kernel is preemptible, we need to freeze all the processes
to prevent them from being in the middle of a pagetable update
@ -86,7 +92,7 @@ static void do_suspend(void)
err = freeze_processes();
if (err) {
printk(KERN_ERR "xen suspend: freeze failed %d\n", err);
goto out;
goto out_destroy_sm;
}
#endif
@ -129,7 +135,11 @@ out_resume:
out_thaw:
#ifdef CONFIG_PREEMPT
thaw_processes();
out_destroy_sm:
#endif
stop_machine_destroy();
out:
shutting_down = SHUTDOWN_INVALID;
}