linux-kernel - [65/67] xen: Do not suspend IPI IRQs.

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Date:	Wed, 11 Aug 2010 17:06:20 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Ian Campbell <ian.campbell@...rix.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	xen-devel@...ts.xensource.com, Thomas Gleixner <tglx@...utronix.de>
Subject: [65/67] xen: Do not suspend IPI IRQs.

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

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

From: Ian Campbell <ian.campbell@...rix.com>

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@...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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 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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