linux-kernel - [PATCH 1/4] UML - Fix spurious IRQ testing

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Date:	Wed, 31 Oct 2007 15:59:38 -0400
From:	Jeff Dike <jdike@...toit.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	uml-devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: [PATCH 1/4] UML - Fix spurious IRQ testing

The spurious IRQ testing in request_irq is mishandled in
um_request_irq, which sets the incoming file descriptors non-blocking
only after request_irq succeeds.  This results in the spurious irq
calling read on a blocking descriptor, and a hang.

Fixed by reversing the O_NONBLOCK setting and the request_irq call.

Signed-off-by: Jeff Dike <jdike@...ux.intel.com>
---
 arch/um/kernel/irq.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

Index: linux-2.6.22/arch/um/kernel/irq.c
===================================================================
--- linux-2.6.22.orig/arch/um/kernel/irq.c	2007-10-25 12:23:09.000000000 -0400
+++ linux-2.6.22/arch/um/kernel/irq.c	2007-10-29 13:00:18.000000000 -0400
@@ -347,14 +347,15 @@ int um_request_irq(unsigned int irq, int
 {
 	int err;
 
-	err = request_irq(irq, handler, irqflags, devname, dev_id);
-	if (err)
-		return err;
-
-	if (fd != -1)
+	if (fd != -1) {
 		err = activate_fd(irq, fd, type, dev_id);
-	return err;
+		if (err)
+			return err;
+	}
+
+	return request_irq(irq, handler, irqflags, devname, dev_id);
 }
+
 EXPORT_SYMBOL(um_request_irq);
 EXPORT_SYMBOL(reactivate_fd);
 
-
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