genirq: Remove paranoid warnons and bogus fixups

Alexander pointed out that the warnons in the regular exit path are
bogus and the thread_mask one actually could be triggered when
__setup_irq() hands out that thread_mask again after __free_irq()
dropped irq_desc->lock.

Thinking more about it, neither IRQTF_RUNTHREAD nor the bit in
thread_mask can be set as this is the regular exit path. We come here
due to:
	__free_irq()
	   remove action from desc
	   synchronize_irq()
	   kthread_stop()

So synchronize_irq() makes sure that the thread finished running and
cleaned up both the thread_active count and thread_mask. After that
point nothing can set IRQTF_RUNTHREAD on this action. So the warnons
and the cleanups are pointless.

Reported-by: Alexander Gordeev <agordeev@redhat.com>
Cc: Ido Yariv <ido@wizery.com>
Link: http://lkml.kernel.org/r/20120315190755.GA6732@dhcp-26-207.brq.redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/irq/manage.c

@@ -804,17 +804,11 @@ static int irq_thread(void *data)
 	 * 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 should be set.
+	 * 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.
 	 *
-	 * Verify that this is true.
-	 */
-	if (WARN_ON(test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags)))
-		wake_threads_waitq(desc);
-
-	if (WARN_ON(desc->threads_oneshot & action->thread_mask))
-		irq_finalize_oneshot(desc, action, true);
-
-	/*
 	 * Clear irq_thread. Otherwise exit_irq_thread() would make
 	 * fuzz about an active irq thread going into nirvana.
 	 */