[Xen-devel] [49/54] xen: Do not suspend IPI IRQs.

[Greg KH <gregkh@xxxxxxx>]

2.6.34-stable review patch.  If anyone has any objections, please let us know.

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

From: Ian Campbell <ian.campbell@xxxxxxxxxx>

commit 4877c737283813bdb4bebfa3168c1585f6e3a8ca upstream.

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@xxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
LKML-Reference: <1280398595-29708-4-git-send-email-ian.campbell@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/xen/events.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -536,6 +536,7 @@ int bind_ipi_to_irqhandler(enum ipi_vect
        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);



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