If this thread is preempted at(or before) location a, 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_INTERRUPTIBLE, if it is preempted again after that and before
__set_current_state(TASK_RUNNING), it triggers the invalid wakeup problem.
----------------
kauditd_thread()
----------------
while (!kthread_should_stop()) {
...
//location a
set_current_state(TASK_INTERRUPTIBLE);
...
if (!skb_queue_len(&audit_skb_queue)) {
//location b
try_to_freeze();
schedule();
//location c
}
__set_current_state(TASK_RUNNING);
//location d
...
}
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.
----------------
kauditd_thread()
----------------
while (!kthread_should_stop()) {
...
preempt_disable();
set_current_state(TASK_INTERRUPTIBLE);
...
if (!skb_queue_len(&audit_skb_queue)) {
preempt_enable();
try_to_freeze();
schedule();
preempt_disable();
}
__set_current_state(TASK_RUNNING);
preempt_enable();
...
}
Signed-off-by: Libin <huawei.li...@huawei.com>
---
kernel/audit.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/audit.c b/kernel/audit.c
index 91e53d0..a7d1346 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -455,15 +455,19 @@ static int kauditd_thread(void *dummy)
audit_printk_skb(skb);
continue;
}
+ preempt_disable();
set_current_state(TASK_INTERRUPTIBLE);
add_wait_queue(&kauditd_wait, &wait);
if (!skb_queue_len(&audit_skb_queue)) {
+ preempt_enable();
try_to_freeze();
schedule();
+ preempt_disable();
}
__set_current_state(TASK_RUNNING);
+ preempt_enable();
remove_wait_queue(&kauditd_wait, &wait);
}
return 0;
--
1.8.2.1
--
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