This is a note to let you know that I've just added the patch titled
genirq: Clear action->thread_mask if IRQ_ONESHOT is not set
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
genirq-clear-action-thread_mask-if-irq_oneshot-is-not-set.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 52abb700e16a9aa4cbc03f3d7f80206cbbc80680 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <[email protected]>
Date: Tue, 6 Mar 2012 23:18:54 +0100
Subject: genirq: Clear action->thread_mask if IRQ_ONESHOT is not set
From: Thomas Gleixner <[email protected]>
commit 52abb700e16a9aa4cbc03f3d7f80206cbbc80680 upstream.
Xommit ac5637611(genirq: Unmask oneshot irqs when thread was not woken)
fails to unmask when a !IRQ_ONESHOT threaded handler is handled by
handle_level_irq.
This happens because thread_mask is or'ed unconditionally in
irq_wake_thread(), but for !IRQ_ONESHOT interrupts never cleared. So
the check for !desc->thread_active fails and keeps the interrupt
disabled.
Keep the thread_mask zero for !IRQ_ONESHOT interrupts.
Document the thread_mask magic while at it.
Reported-and-tested-by: Sven Joachim <[email protected]>
Reported-and-tested-by: Stefan Lippers-Hollmann <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/irq/manage.c | 44 ++++++++++++++++++++++++++++++++++++++------
1 file changed, 38 insertions(+), 6 deletions(-)
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -976,6 +976,11 @@ __setup_irq(unsigned int irq, struct irq
/* add new interrupt at end of irq queue */
do {
+ /*
+ * Or all existing action->thread_mask bits,
+ * so we can find the next zero bit for this
+ * new action.
+ */
thread_mask |= old->thread_mask;
old_ptr = &old->next;
old = *old_ptr;
@@ -984,14 +989,41 @@ __setup_irq(unsigned int irq, struct irq
}
/*
- * Setup the thread mask for this irqaction. Unlikely to have
- * 32 resp 64 irqs sharing one line, but who knows.
+ * Setup the thread mask for this irqaction for ONESHOT. For
+ * !ONESHOT irqs the thread mask is 0 so we can avoid a
+ * conditional in irq_wake_thread().
*/
- if (new->flags & IRQF_ONESHOT && thread_mask == ~0UL) {
- ret = -EBUSY;
- goto out_mask;
+ if (new->flags & IRQF_ONESHOT) {
+ /*
+ * Unlikely to have 32 resp 64 irqs sharing one line,
+ * but who knows.
+ */
+ if (thread_mask == ~0UL) {
+ ret = -EBUSY;
+ goto out_mask;
+ }
+ /*
+ * The thread_mask for the action is or'ed to
+ * desc->thread_active to indicate that the
+ * IRQF_ONESHOT thread handler has been woken, but not
+ * yet finished. The bit is cleared when a thread
+ * completes. When all threads of a shared interrupt
+ * line have completed desc->threads_active becomes
+ * zero and the interrupt line is unmasked. See
+ * handle.c:irq_wake_thread() for further information.
+ *
+ * If no thread is woken by primary (hard irq context)
+ * interrupt handlers, then desc->threads_active is
+ * also checked for zero to unmask the irq line in the
+ * affected hard irq flow handlers
+ * (handle_[fasteoi|level]_irq).
+ *
+ * The new action gets the first zero bit of
+ * thread_mask assigned. See the loop above which or's
+ * all existing action->thread_mask bits.
+ */
+ new->thread_mask = 1 << ffz(thread_mask);
}
- new->thread_mask = 1 << ffz(thread_mask);
if (!shared) {
init_waitqueue_head(&desc->wait_for_threads);
Patches currently in stable-queue which might be from [email protected] are
queue-3.0/genirq-clear-action-thread_mask-if-irq_oneshot-is-not-set.patch
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