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Subject[tip:irq/core] genirq: Remove paranoid warnons and bogus fixups
Commit-ID:  e04268b0effc0ceea366c50b3107baad9edadafa
Gitweb: http://git.kernel.org/tip/e04268b0effc0ceea366c50b3107baad9edadafa
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Thu, 15 Mar 2012 22:55:21 +0100
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 16 Mar 2012 11:27:28 +0100

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 | 14 ++++----------
1 files changed, 4 insertions(+), 10 deletions(-)
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 453feed..b0ccd1a 100644
--- a/kernel/irq/manage.c
+++ b/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.
*/

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