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

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Message-ID: <tip-4877c737283813bdb4bebfa3168c1585f6e3a8ca@git.kernel.org>
Date:	Thu, 29 Jul 2010 11:31:44 GMT
From:	tip-bot for Ian Campbell <ian.campbell@...rix.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, jeremy@...p.org, hpa@...or.com,
	mingo@...hat.com, ian.campbell@...rix.com, tglx@...utronix.de
Subject: [tip:irq/core] xen: Do not suspend IPI IRQs.

Commit-ID:  4877c737283813bdb4bebfa3168c1585f6e3a8ca
Gitweb:     http://git.kernel.org/tip/4877c737283813bdb4bebfa3168c1585f6e3a8ca
Author:     Ian Campbell <ian.campbell@...rix.com>
AuthorDate: Thu, 29 Jul 2010 11:16:35 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
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@...rix.com>
Cc: Jeremy Fitzhardinge <jeremy@...p.org>
Cc: xen-devel@...ts.xensource.com
LKML-Reference: <1280398595-29708-4-git-send-email-ian.campbell@...rix.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 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);
--
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