[67/80] genirq: Fix race condition when stopping the irq thread

Greg KH
2011-12-07T16:19:07Z

From: Ido Yariv <ido@wizery.com>

commit 550acb19269d65f32e9ac4ddb26c2b2070e37f1c upstream.

In irq_wait_for_interrupt(), the should_stop member is verified before
setting the task's state to TASK_INTERRUPTIBLE and calling schedule().
In case kthread_stop sets should_stop and wakes up the process after
should_stop is checked by the irq thread but before the task's state
is changed, the irq thread might never exit:

kthread_stop irq_wait_for_interrupt
------------ ----------------------

...
... while (!kthread_should_stop()) {
kthread->should_stop = 1;
wake_up_process(k);
wait_for_completion(&kthread->exited);
...
set_current_state(TASK_INTERRUPTIBLE);

...

schedule();
}

Fix this by checking if the thread should stop after modifying the
task's state.

[ tglx: Simplified it a bit ]

Signed-off-by: Ido Yariv <ido@wizery.com>
Link: http://lkml.kernel.org/r/1322740508-22640-1-git-send-email-ido@wizery.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
kernel/irq/manage.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -620,8 +620,9 @@ static irqreturn_t irq_nested_primary_ha

static int irq_wait_for_interrupt(struct irqaction *action)
{
+ set_current_state(TASK_INTERRUPTIBLE);
+
while (!kthread_should_stop()) {
- set_current_state(TASK_INTERRUPTIBLE);

if (test_and_clear_bit(IRQTF_RUNTHREAD,
&action->thread_flags)) {
@@ -629,7 +630,9 @@ static int irq_wait_for_interrupt(struct
return 0;
}
schedule();
+ set_current_state(TASK_INTERRUPTIBLE);
}
+ __set_current_state(TASK_RUNNING);
return -1;
}