1 files changed, 76 insertions, 54 deletions

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 32313c08444..b0ccd1ac2d6 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -759,6 +759,13 @@ static irqreturn_t irq_thread_fn(struct irq_desc *desc,
 	return ret;
 }
 
+static void wake_threads_waitq(struct irq_desc *desc)
+{
+	if (atomic_dec_and_test(&desc->threads_active) &&
+	    waitqueue_active(&desc->wait_for_threads))
+		wake_up(&desc->wait_for_threads);
+}
+
 /*
  * Interrupt handler thread
  */
@@ -771,57 +778,41 @@ static int irq_thread(void *data)
 	struct irq_desc *desc = irq_to_desc(action->irq);
 	irqreturn_t (*handler_fn)(struct irq_desc *desc,
 			struct irqaction *action);
-	int wake;
 
-	if (force_irqthreads & test_bit(IRQTF_FORCED_THREAD,
+	if (force_irqthreads && test_bit(IRQTF_FORCED_THREAD,
 					&action->thread_flags))
 		handler_fn = irq_forced_thread_fn;
 	else
 		handler_fn = irq_thread_fn;
 
 	sched_setscheduler(current, SCHED_FIFO, &param);
-	current->irqaction = action;
+	current->irq_thread = 1;
 
 	while (!irq_wait_for_interrupt(action)) {
+		irqreturn_t action_ret;
 
 		irq_thread_check_affinity(desc, action);
 
-		atomic_inc(&desc->threads_active);
-
-		raw_spin_lock_irq(&desc->lock);
-		if (unlikely(irqd_irq_disabled(&desc->irq_data))) {
-			/*
-			 * CHECKME: We might need a dedicated
-			 * IRQ_THREAD_PENDING flag here, which
-			 * retriggers the thread in check_irq_resend()
-			 * but AFAICT IRQS_PENDING should be fine as it
-			 * retriggers the interrupt itself --- tglx
-			 */
-			desc->istate |= IRQS_PENDING;
-			raw_spin_unlock_irq(&desc->lock);
-		} else {
-			irqreturn_t action_ret;
-
-			raw_spin_unlock_irq(&desc->lock);
-			action_ret = handler_fn(desc, action);
-			if (!noirqdebug)
-				note_interrupt(action->irq, desc, action_ret);
-		}
+		action_ret = handler_fn(desc, action);
+		if (!noirqdebug)
+			note_interrupt(action->irq, desc, action_ret);
 
-		wake = atomic_dec_and_test(&desc->threads_active);
-
-		if (wake && waitqueue_active(&desc->wait_for_threads))
-			wake_up(&desc->wait_for_threads);
+		wake_threads_waitq(desc);
 	}
 
-	/* Prevent a stale desc->threads_oneshot */
-	irq_finalize_oneshot(desc, action, true);
-
 	/*
-	 * Clear irqaction. Otherwise exit_irq_thread() would make
+	 * This is the regular exit path. __free_irq() is stopping the
+	 * thread via kthread_stop() after calling
+	 * synchronize_irq(). So neither IRQTF_RUNTHREAD nor the
+	 * oneshot mask bit can be set. We cannot verify that as we
+	 * cannot touch the oneshot mask at this point anymore as
+	 * __setup_irq() might have given out currents thread_mask
+	 * again.
+	 *
+	 * Clear irq_thread. Otherwise exit_irq_thread() would make
 	 * fuzz about an active irq thread going into nirvana.
 	 */
-	current->irqaction = NULL;
+	current->irq_thread = 0;
 	return 0;
 }
 
@@ -832,27 +823,28 @@ void exit_irq_thread(void)
 {
 	struct task_struct *tsk = current;
 	struct irq_desc *desc;
+	struct irqaction *action;
 
-	if (!tsk->irqaction)
+	if (!tsk->irq_thread)
 		return;
 
+	action = kthread_data(tsk);
+
 	printk(KERN_ERR
 	       "exiting task \"%s\" (%d) is an active IRQ thread (irq %d)\n",
-	       tsk->comm ? tsk->comm : "", tsk->pid, tsk->irqaction->irq);
+	       tsk->comm ? tsk->comm : "", tsk->pid, action->irq);
 
-	desc = irq_to_desc(tsk->irqaction->irq);
+	desc = irq_to_desc(action->irq);
 
 	/*
-	 * Prevent a stale desc->threads_oneshot. Must be called
-	 * before setting the IRQTF_DIED flag.
+	 * If IRQTF_RUNTHREAD is set, we need to decrement
+	 * desc->threads_active and wake possible waiters.
 	 */
-	irq_finalize_oneshot(desc, tsk->irqaction, true);
+	if (test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags))
+		wake_threads_waitq(desc);
 
-	/*
-	 * Set the THREAD DIED flag to prevent further wakeups of the
-	 * soon to be gone threaded handler.
-	 */
-	set_bit(IRQTF_DIED, &tsk->irqaction->flags);
+	/* Prevent a stale desc->threads_oneshot */
+	irq_finalize_oneshot(desc, action, true);
 }
 
 static void irq_setup_forced_threading(struct irqaction *new)
@@ -985,6 +977,11 @@ __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 +990,41 @@ __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);
@@ -1103,8 +1127,7 @@ out_thread:
 		struct task_struct *t = new->thread;
 
 		new->thread = NULL;
-		if (likely(!test_bit(IRQTF_DIED, &new->thread_flags)))
-			kthread_stop(t);
+		kthread_stop(t);
 		put_task_struct(t);
 	}
 out_mput:
@@ -1214,8 +1237,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 #endif
 
 	if (action->thread) {
-		if (!test_bit(IRQTF_DIED, &action->thread_flags))
-			kthread_stop(action->thread);
+		kthread_stop(action->thread);
 		put_task_struct(action->thread);
 	}