goto out;
}
+ /*
+ * Guarantee this task is visible on the waitqueue before
+ * checking the wake condition.
+ *
+ * The full memory barrier within set_current_state() of
+ * prepare_to_wait_event() pairs with the full memory barrier
+ * within wq_has_sleeper().
+ *
+ * This pairs with wake_up_klogd:A.
+ */
ret = wait_event_interruptible(log_wait,
- prb_read_valid(prb, atomic64_read(&user->seq), r));
+ prb_read_valid(prb,
+ atomic64_read(&user->seq), r)); /* LMM(devkmsg_read:A) */
if (ret)
goto out;
}
seq = syslog_seq;
mutex_unlock(&syslog_lock);
- len = wait_event_interruptible(log_wait, prb_read_valid(prb, seq, NULL));
+ /*
+ * Guarantee this task is visible on the waitqueue before
+ * checking the wake condition.
+ *
+ * The full memory barrier within set_current_state() of
+ * prepare_to_wait_event() pairs with the full memory barrier
+ * within wq_has_sleeper().
+ *
+ * This pairs with wake_up_klogd:A.
+ */
+ len = wait_event_interruptible(log_wait,
+ prb_read_valid(prb, seq, NULL)); /* LMM(syslog_print:A) */
mutex_lock(&syslog_lock);
if (len)
return;
preempt_disable();
- if (waitqueue_active(&log_wait)) {
+ /*
+ * Guarantee any new records can be seen by tasks preparing to wait
+ * before this context checks if the wait queue is empty.
+ *
+ * The full memory barrier within wq_has_sleeper() pairs with the full
+ * memory barrier within set_current_state() of
+ * prepare_to_wait_event(), which is called after ___wait_event() adds
+ * the waiter but before it has checked the wait condition.
+ *
+ * This pairs with devkmsg_read:A and syslog_print:A.
+ */
+ if (wq_has_sleeper(&log_wait)) { /* LMM(wake_up_klogd:A) */
this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
}