This is a note to let you know that I've just added the patch titled
genirq: Disable the SHIRQ_DEBUG call in request_threaded_irq for now
to the 2.6.32-longterm tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/longterm/longterm-queue-2.6.32.git;a=summary
The filename of the patch is:
genirq-disable-the-shirq_debug-call-in-request_threaded_irq-for-now.patch
and it can be found in the queue-2.6.32 subdirectory.
If you, or anyone else, feels it should not be added to the 2.6.32 longterm
tree,
please let <[email protected]> know about it.
>From 6d83f94db95cfe65d2a6359cccdf61cf087c2598 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <[email protected]>
Date: Fri, 18 Feb 2011 23:27:23 +0100
Subject: genirq: Disable the SHIRQ_DEBUG call in request_threaded_irq for now
From: Thomas Gleixner <[email protected]>
commit 6d83f94db95cfe65d2a6359cccdf61cf087c2598 upstream.
With CONFIG_SHIRQ_DEBUG=y we call a newly installed interrupt handler
in request_threaded_irq().
The original implementation (commit a304e1b8) called the handler
_BEFORE_ it was installed, but that caused problems with handlers
calling disable_irq_nosync(). See commit 377bf1e4.
It's braindead in the first place to call disable_irq_nosync in shared
handlers, but ....
Moving this call after we installed the handler looks innocent, but it
is very subtle broken on SMP.
Interrupt handlers rely on the fact, that the irq core prevents
reentrancy.
Now this debug call violates that promise because we run the handler
w/o the IRQ_INPROGRESS protection - which we cannot apply here because
that would result in a possibly forever masked interrupt line.
A concurrent real hardware interrupt on a different CPU results in
handler reentrancy and can lead to complete wreckage, which was
unfortunately observed in reality and took a fricking long time to
debug.
Leave the code here for now. We want this debug feature, but that's
not easy to fix. We really should get rid of those
disable_irq_nosync() abusers and remove that function completely.
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Anton Vorontsov <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/irq/manage.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1079,7 +1079,7 @@ int request_threaded_irq(unsigned int ir
if (retval)
kfree(action);
-#ifdef CONFIG_DEBUG_SHIRQ
+#ifdef CONFIG_DEBUG_SHIRQ_FIXME
if (irqflags & IRQF_SHARED) {
/*
* It's a shared IRQ -- the driver ought to be prepared for it
Patches currently in longterm-queue-2.6.32 which might be from
[email protected] are
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