Hi 2012/11/19 Oleg Nesterov <[email protected]>: > > Because on a second thought I suspect this change is wrong. > > Just for example, please look at kauditd_thread(). It does > > set_current_state(TASK_INTERRUPTIBLE); > > add_wait_queue(&kauditd_wait, &wait); > > if (!CONDITION) // <-- LOAD > schedule(); > > And the last LOAD can leak into the critical section protected by > wait_queue_head_t->lock, and it can be reordered with list_add() > inside this critical section. In this case we can race with wake_up() > unless it takes the same lock. > > Oleg. >
I agree that I should solve my problem using the waitqueue_active() function locally. I'll abandon this patch and fix it in the tty_ldisc.c. But we try to understand your fault scenario: How can the LOAD leak into the critical section? As far as we understand the spin_unlock() function also contains a memory barrier to prevent such a reordering from happening. Regards, Ivo -- 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/
