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    Subject[PATCH 4/4] xen: do not suspend IPI IRQs.
    Date
    In general the semantics of IPIs are that they are are expected to
    continue functioning after dpm_suspend_noirq().

    Specifically I have seen a deadlock between the callfunc IPI and the
    stop machine used by xen's do_suspend() routine. If one CPU has already
    called dpm_suspend_noirq() then there is a window where it can be sent
    a callfunc IPI before all the other CPUs have entered stop_cpu().

    If this happens then the first CPU ends up spinning in stop_cpu()
    waiting for the other to rendezvous in state STOPMACHINE_PREPARE while
    the other is spinning in csd_lock_wait().

    Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Jeremy Fitzhardinge <jeremy@goop.org>
    Cc: xen-devel@lists.xensource.com
    Cc: <stable@kernel.org> # .32.x+: 517d6934: irq: rename IRQF_TIMER to IRQF_NO_SUSPEND
    Cc: <stable@kernel.org> # .32.x+
    ---
    drivers/xen/events.c | 1 +
    1 files changed, 1 insertions(+), 0 deletions(-)

    diff --git a/drivers/xen/events.c b/drivers/xen/events.c
    index db8f506..28f133a 100644
    --- a/drivers/xen/events.c
    +++ b/drivers/xen/events.c
    @@ -536,6 +536,7 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
    if (irq < 0)
    return irq;

    + irqflags |= IRQF_NO_SUSPEND;
    retval = request_irq(irq, handler, irqflags, devname, dev_id);
    if (retval != 0) {
    unbind_from_irq(irq);
    --
    1.5.6.5


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