If thread is preempted before calling set_current_state(TASK_UNINTERRUPTIBLE),
and the other thread set the condition followed with wake_up_process. After
that when this thread is re-scheduled, calling set_current_state to set itself
as state TASK_UNINTERRUPTIBLE, if it is preempted again after that and before
__set_current_state(TASK_RUNNING), it triggers the invalid wakeup problem.
--------------
klist_remove()
--------------
...
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (waiter.woken)
break;
schedule();
}
__set_current_state(TASK_RUNNING);
...
To solve this problem, using preempt_disable() to bound the operaion that
setting the task state and the conditions(set by the wake thread) validation.
--------------
klist_remove()
--------------
...
preempt_disable();
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (waiter.woken)
break;
preempt_enable();
schedule();
preempt_disable();
}
__set_current_state(TASK_RUNNING);
preempt_enable();
...
Signed-off-by: Libin <huawei.li...@huawei.com>
---
lib/klist.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/lib/klist.c b/lib/klist.c
index 358a368..e7c7208 100644
--- a/lib/klist.c
+++ b/lib/klist.c
@@ -249,13 +249,17 @@ void klist_remove(struct klist_node *n)
klist_del(n);
+ preempt_disable();
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (waiter.woken)
break;
+ preempt_enable();
schedule();
+ preempt_disable();
}
__set_current_state(TASK_RUNNING);
+ preempt_enable();
}
EXPORT_SYMBOL_GPL(klist_remove);
--
1.8.2.1
--
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