There is below race between irq handler and irq thread:
irq handler irq thread
irq_wake_thread() irq_thread()
set bit RUNTHREAD
... clear bit RUNTHREAD
thread_fn()
[A]test_and_decrease
thread_active
[B]increase thread_active
If action A is before action B, after that the thread_active
will be always > 0, and for synchronize_irq() calling, which
will be waiting there forever.
Here put the increasing thread-active before setting bit
RUNTHREAD, which can resolve such race.
Signed-off-by: xiaoming wang <xiaoming.w...@intel.com>
Signed-off-by: Chuansheng Liu <chuansheng....@intel.com>
---
kernel/irq/handle.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 131ca17..5f9fbb7 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -65,7 +65,7 @@ static void irq_wake_thread(struct irq_desc *desc, struct
irqaction *action)
* Wake up the handler thread for this action. If the
* RUNTHREAD bit is already set, nothing to do.
*/
- if (test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags))
+ if (test_bit(IRQTF_RUNTHREAD, &action->thread_flags))
return;
/*
@@ -126,6 +126,25 @@ static void irq_wake_thread(struct irq_desc *desc, struct
irqaction *action)
*/
atomic_inc(&desc->threads_active);
+ /*
+ * set the RUNTHREAD bit after increasing the threads_active,
+ * it can avoid the below race:
+ * irq handler irq thread in case it is in
+ * running state
+ *
+ * set RUNTHREAD bit
+ * clear the RUNTHREAD bit
+ *... thread_fn()
+ *
+ * due to threads_active==0,
+ * no waking up wait_for_threads
+ *
+ * threads_active ++
+ * After that, the threads_active will be always > 0, which
+ * will block the synchronize_irq().
+ */
+ set_bit(IRQTF_RUNTHREAD, &action->thread_flags);
+
wake_up_process(action->thread);
}
--
1.9.rc0
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