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Commit 52abb700 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds
Browse files

genirq: Clear action->thread_mask if IRQ_ONESHOT is not set 



Xommit ac563761(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: default avatarSven Joachim <svenjoac@gmx.de>
Reported-and-tested-by: default avatarStefan Lippers-Hollmann <s.l-h@gmx.de>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ce8fea7a

kernel/irq/manage.c

+38 −6
Original line number Diff line number Diff line
@@ -985,6 +985,11 @@ __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;
@@ -993,14 +998,41 @@ __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) {

	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);

	}



	if (!shared) {

		init_waitqueue_head(&desc->wait_for_threads);