Messages in this thread Patch in this message | | | From | Libin <> | Subject | [PATCH 02/14] audit: Fix invalid wakeup in kauditd_thread | Date | Thu, 29 Aug 2013 21:57:37 +0800 |
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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.libin@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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