genirq: Get rid of unnecessary IRQTF_DIED flag

Currently IRQTF_DIED flag is set when a IRQ thread handler calls do_exit()
But also PF_EXITING per process flag gets set when a thread exits. This
fix eliminates the duplicate by using PF_EXITING flag.

Also, there is a race condition in exit_irq_thread(). In case a thread's
bit is cleared in desc->threads_oneshot (and the IRQ line gets unmasked),
but before IRQTF_DIED flag is set, a new interrupt might come in and set
just cleared bit again, this time forever. This fix throws IRQTF_DIED flag
away, eliminating the race as a result.

[ tglx: Test THREAD_EXITING first as suggested by Oleg ]

Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Link: http://lkml.kernel.org/r/20120309135958.GD2114@dhcp-26-207.brq.redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 1 insertions, 10 deletions

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 3feab4ab6877..a94466db73b2 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -845,17 +845,8 @@ void exit_irq_thread(void)
 
         desc = irq_to_desc(action->irq);
 
-        /*
-         * Prevent a stale desc->threads_oneshot. Must be called
-         * before setting the IRQTF_DIED flag.
-         */
+        /* Prevent a stale desc->threads_oneshot */
         irq_finalize_oneshot(desc, action, true);
-
-        /*
-         * Set the THREAD DIED flag to prevent further wakeups of the
-         * soon to be gone threaded handler.
-         */
-        set_bit(IRQTF_DIED, &action->flags);
 }
 
 static void irq_setup_forced_threading(struct irqaction *new)