Message-ID: <49754AB5.3000701@hathawaymix.org>
Date: Mon, 19 Jan 2009 20:53:25 -0700
From: Shane Hathaway <shane@hathawaymix.org>
MIME-Version: 1.0
Subject: [uml-devel] [Patch] UML: spurious interrupt freezes guest
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Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net
To: linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net

A new instance of user mode linux that I created over the past couple of
days worked pretty well except that it had a habit of freezing after a
few minutes.  Every time it froze, the last message on the console was
either:

spurious interrupt in ubd_handler, err = 4

or:

spurious interrupt in ubd_handler, err = 0

This message is generated by arch/um/drivers/ubd_kern.c.  I did not work
out the cause of the spurious interrupts, but I did come up with a patch
that makes the guest recover from spurious interrupts without freezing.
 It appears that the interrupt handler needs to be reactivated before
every exit of ubd_handler().  The patch is below.

Shane


--- linux-2.6.27.12-orig/arch/um/drivers/ubd_kern.c
+++ linux-2.6.27.12/arch/um/drivers/ubd_kern.c
@@ -489,6 +489,7 @@
                                break;
                        printk(KERN_ERR "spurious interrupt in
ubd_handler, "
                               "err = %d\n", -n);
+                       reactivate_fd(thread_fd, UBD_IRQ);
                        return;
                }


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