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    Subject[PATCH 3.13 022/163] xen/manage: Always freeze/thaw processes when suspend/resuming
    Date
    3.13.11.9 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Ross Lagerwall <ross.lagerwall@citrix.com>

    commit 61a734d305e16944b42730ef582a7171dc733321 upstream.

    Always freeze processes when suspending and thaw processes when resuming
    to prevent a race noticeable with HVM guests.

    This prevents a deadlock where the khubd kthread (which is designed to
    be freezable) acquires a usb device lock and then tries to allocate
    memory which requires the disk which hasn't been resumed yet.
    Meanwhile, the xenwatch thread deadlocks waiting for the usb device
    lock.

    Freezing processes fixes this because the khubd thread is only thawed
    after the xenwatch thread finishes resuming all the devices.

    Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
    Signed-off-by: David Vrabel <david.vrabel@citrix.com>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    drivers/xen/manage.c | 7 -------
    1 file changed, 7 deletions(-)

    diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
    index 0bc8086..a344372 100644
    --- a/drivers/xen/manage.c
    +++ b/drivers/xen/manage.c
    @@ -110,16 +110,11 @@ static void do_suspend(void)

    shutting_down = SHUTDOWN_SUSPEND;

    -#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
    - during suspend. */
    err = freeze_processes();
    if (err) {
    pr_err("%s: freeze failed %d\n", __func__, err);
    goto out;
    }
    -#endif

    err = dpm_suspend_start(PMSG_FREEZE);
    if (err) {
    @@ -172,10 +167,8 @@ out_resume:
    dpm_resume_end(si.cancelled ? PMSG_THAW : PMSG_RESTORE);

    out_thaw:
    -#ifdef CONFIG_PREEMPT
    thaw_processes();
    out:
    -#endif
    shutting_down = SHUTDOWN_INVALID;
    }
    #endif /* CONFIG_HIBERNATE_CALLBACKS */
    --
    1.9.1


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