If thread is preempted before calling set_current_state(TASK_INTERRUPTIBLE), 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.
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 <[email protected]> --- kernel/rcutree.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/rcutree.h b/kernel/rcutree.h index b383258..e3f1278 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -357,13 +357,17 @@ struct rcu_data { #define rcu_wait(cond) \ do { \ + preempt_disable(); \ for (;;) { \ set_current_state(TASK_INTERRUPTIBLE); \ if (cond) \ break; \ + preempt_enable(); \ schedule(); \ + preempt_disable(); \ } \ __set_current_state(TASK_RUNNING); \ + preempt_enable(); \ } while (0) /* -- 1.8.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
