+static int apm_suspend_notifier(struct notifier_block *nb,
+ unsigned long event,
+ void *dummy)
+{
+ struct apm_user *as;
+ int err;
+
+ /* short-cut emergency suspends */
+ if (atomic_read(&userspace_notification_inhibit))
+ return NOTIFY_DONE;
+
+ switch (event) {
+ case PM_SUSPEND_PREPARE:
+ /*
+ * Queue an event to all "writer" users that we want
+ * to suspend and need their ack.
+ */
+ mutex_lock(&state_lock);
+ down_read(&user_list_lock);
+
+ list_for_each_entry(as, &apm_user_list, list) {
+ if (as->suspend_state != SUSPEND_WAIT && as->reader &&
+ as->writer && as->suser) {
+ as->suspend_state = SUSPEND_PENDING;
+ atomic_inc(&suspend_acks_pending);
+ queue_add_event(&as->queue, APM_USER_SUSPEND);
+ }
+ }
+
+ up_read(&user_list_lock);
+ mutex_unlock(&state_lock);
+ wake_up_interruptible(&apm_waitqueue);
+
+ /*
+ * Wait for the the suspend_acks_pending variable to drop to
+ * zero, meaning everybody acked the suspend event (or the
+ * process was killed.)
+ *
+ * If the app won't answer within a short while we assume it
+ * locked up and ignore it.
+ */
+ err = wait_event_interruptible_timeout(
+ apm_suspend_waitqueue,
+ atomic_read(&suspend_acks_pending) == 0,
+ 5*HZ);
+
+ /* timed out */
+ if (err == 0) {
+ /*
+ * Move anybody who timed out to "ack timeout" state.
+ *
+ * We could time out and the userspace does the ACK
+ * right after we time out but before we enter the
+ * locked section here, but that's fine.
+ */
+ mutex_lock(&state_lock);
+ down_read(&user_list_lock);
+ list_for_each_entry(as, &apm_user_list, list) {
+ if (as->suspend_state == SUSPEND_PENDING ||
+ as->suspend_state == SUSPEND_READ) {
+ as->suspend_state = SUSPEND_ACKTO;
+ atomic_dec(&suspend_acks_pending);
+ }
+ }
+ up_read(&user_list_lock);
+ mutex_unlock(&state_lock);
+ }
+
+ /* let suspend proceed */
+ if (err >= 0)
+ return NOTIFY_OK;
+
+ /* interrupted by signal */
+ return NOTIFY_BAD;
+
+ case PM_POST_SUSPEND:
+ /*
+ * Anyone on the APM queues will think we're still suspended.
+ * Send a message so everyone knows we're now awake again.
+ */
+ queue_event(APM_NORMAL_RESUME);
+
+ /*
+ * Finally, wake up anyone who is sleeping on the suspend.
+ */
+ mutex_lock(&state_lock);
+ down_read(&user_list_lock);
+ list_for_each_entry(as, &apm_user_list, list) {
+ if (as->suspend_state == SUSPEND_ACKED) {
+ /*
+ * TODO: maybe grab error code, needs core
+ * changes to push the error to the notifier
+ * chain (could use the second parameter if
+ * implemented)
+ */
+ as->suspend_result = 0;
+ as->suspend_state = SUSPEND_DONE;
+ }
+ }
+ up_read(&user_list_lock);
+ mutex_unlock(&state_lock);
+
+ wake_up(&apm_suspend_waitqueue);
+ return NOTIFY_OK;
+
+ default:
+ return NOTIFY_DONE;
+ }
+}
+
+static struct notifier_block apm_notif_block = {
+ .notifier_call = apm_suspend_notifier,
+};
+