git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From b4606f2165153833247823e8c04c5e88cb3d298b Mon Sep 17 00:00:00 2001
   2 From: Ian Campbell <ian.campbell@citrix.com>
   3 Date: Tue, 1 Dec 2009 11:47:15 +0000
   4 Subject: xen: explicitly create/destroy stop_machine workqueues outside suspend/resume region.
   5
   6 From: Ian Campbell <ian.campbell@citrix.com>
   7
   8 commit b4606f2165153833247823e8c04c5e88cb3d298b upstream.
   9
  10 I have observed cases where the implicit stop_machine_destroy() done by
  11 stop_machine() hangs while destroying the workqueues, specifically in
  12 kthread_stop(). This seems to be because timer ticks are not restarted
  13 until after stop_machine() returns.
  14
  15 Fortunately stop_machine provides a facility to pre-create/post-destroy
  16 the workqueues so use this to ensure that workqueues are only destroyed
  17 after everything is really up and running again.
  18
  19 I only actually observed this failure with 2.6.30. It seems that newer
  20 kernels are somehow more robust against doing kthread_stop() without timer
  21 interrupts (I tried some backports of some likely looking candidates but
  22 did not track down the commit which added this robustness). However this
  23 change seems like a reasonable belt&braces thing to do.
  24
  25 Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
  26 Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
  27 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  28
  29 ---
  30  drivers/xen/manage.c |   12 +++++++++++-
  31  1 file changed, 11 insertions(+), 1 deletion(-)
  32
  33 --- a/drivers/xen/manage.c
  34 +++ b/drivers/xen/manage.c
  35 @@ -79,6 +79,12 @@ static void do_suspend(void)
  36
  37         shutting_down = SHUTDOWN_SUSPEND;
  38
  39 +       err = stop_machine_create();
  40 +       if (err) {
  41 +               printk(KERN_ERR "xen suspend: failed to setup stop_machine %d\n", err);
  42 +               goto out;
  43 +       }
  44 +
  45  #ifdef CONFIG_PREEMPT
  46         /* If the kernel is preemptible, we need to freeze all the processes
  47            to prevent them from being in the middle of a pagetable update
  48 @@ -86,7 +92,7 @@ static void do_suspend(void)
  49         err = freeze_processes();
  50         if (err) {
  51                 printk(KERN_ERR "xen suspend: freeze failed %d\n", err);
  52 -               goto out;
  53 +               goto out_destroy_sm;
  54         }
  55  #endif
  56
  57 @@ -129,7 +135,11 @@ out_resume:
  58  out_thaw:
  59  #ifdef CONFIG_PREEMPT
  60         thaw_processes();
  61 +
  62 +out_destroy_sm:
  63  #endif
  64 +       stop_machine_destroy();
  65 +
  66  out:
  67         shutting_down = SHUTDOWN_INVALID;
  68  }