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authorThomas Gleixner <tglx@linutronix.de>2012-03-06 23:18:54 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-03-12 10:32:53 -0700
commitc847ac8e8e7447730aef70b94915f1c0880e6578 (patch)
treedbc1fb211b26eb9f7cc59d38641e4779e1ede88d
parentd7838b04ecb08709b09063a8ada0aa2d29636c12 (diff)
downloadlwn-c847ac8e8e7447730aef70b94915f1c0880e6578.tar.gz
lwn-c847ac8e8e7447730aef70b94915f1c0880e6578.zip
genirq: Clear action->thread_mask if IRQ_ONESHOT is not set
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 <svenjoac@gmx.de> Reported-and-tested-by: Stefan Lippers-Hollmann <s.l-h@gmx.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/irq/manage.c44
1 files changed, 38 insertions, 6 deletions
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index def3406fb43b..e4eedb161971 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -976,6 +976,11 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
/* 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_desc *desc, struct irqaction *new)
}
/*
- * 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);