kern/sleepq: fix signal behaviour

In order to correctly implement the behaviour of condition_signal, which
must wake up at least one waiting thread if there's any, sleepq_signal
wakes up the oldest waiter and shifts it.

The FIFO behaviour is removed from the specification, as the only user
which relied on it was a previous condition variable implementation.

1 files changed, 4 insertions, 2 deletions

diff --git a/kern/sleepq.c b/kern/sleepq.c
index bd0e363..0d04c6e 100644
--- a/kern/sleepq.c
+++ b/kern/sleepq.c
@@ -492,11 +492,13 @@ sleepq_signal(struct sleepq *sleepq)
 {
     struct sleepq_waiter *waiter;
 
-    if (list_empty(&sleepq->waiters)) {
+    waiter = sleepq->oldest_waiter;
+
+    if (!waiter) {
         return;
     }
 
-    waiter = list_last_entry(&sleepq->waiters, struct sleepq_waiter, node);
+    sleepq_shift_oldest_waiter(sleepq);
     sleepq_waiter_set_pending_wakeup(waiter);
     sleepq_waiter_wakeup(waiter);
 }