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    Subject[096/151] xen: explicitly create/destroy stop_machine workqueues outside suspend/resume region.
    2.6.32-stable review patch.  If anyone has any objections, please let us know.


    From: Ian Campbell <>

    commit b4606f2165153833247823e8c04c5e88cb3d298b upstream.

    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 <>
    Signed-off-by: Jeremy Fitzhardinge <>
    Signed-off-by: Greg Kroah-Hartman <>

    drivers/xen/manage.c | 12 +++++++++++-
    1 file changed, 11 insertions(+), 1 deletion(-)

    --- a/drivers/xen/manage.c
    +++ b/drivers/xen/manage.c
    @@ -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;
    + }
    /* 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;

    @@ -129,7 +135,11 @@ out_resume:
    + stop_machine_destroy();
    shutting_down = SHUTDOWN_INVALID;

     \ /
      Last update: 2009-12-17 05:29    [W:0.023 / U:395.908 seconds]
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