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.
----------------------
zap_pid_ns_processes()
----------------------
...
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (pid_ns->nr_hashed == init_pids)
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.
Signed-off-by: Libin <huawei.li...@huawei.com>
---
kernel/pid_namespace.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 6917e8e..e3696a1 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -227,13 +227,17 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
* sys_wait4() above can't reap the TASK_DEAD children.
* Make sure they all go away, see free_pid().
*/
+ preempt_disable();
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (pid_ns->nr_hashed == init_pids)
break;
+ preempt_enable();
schedule();
+ preempt_disable();
}
__set_current_state(TASK_RUNNING);
+ preempt_enable();
if (pid_ns->reboot)
current->signal->group_exit_code = pid_ns->reboot;
--
1.8.2.1
--
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