[tip:irq/core] xen: Do not suspend IPI IRQs.

From: tip-bot for Ian Campbell
Date: Thu Jul 29 2010 - 07:32:07 EST

Commit-ID: 4877c737283813bdb4bebfa3168c1585f6e3a8ca
Gitweb: http://git.kernel.org/tip/4877c737283813bdb4bebfa3168c1585f6e3a8ca
Author: Ian Campbell <ian.campbell@xxxxxxxxxx>
AuthorDate: Thu, 29 Jul 2010 11:16:35 +0100
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Thu, 29 Jul 2010 13:24:58 +0200

xen: Do not suspend IPI IRQs.

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>
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) {
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