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Update sema_up to yield CPU if unblocked has higher priority

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sBubshait
2024-10-17 07:15:10 +01:00
parent 24900545d4
commit 0d6fb2f167
1 changed files with 14 additions and 3 deletions
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17
src/threads/synch.c
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@@ -114,11 +114,22 @@ sema_up (struct semaphore *sema)
ASSERT (sema != NULL);
old_level = intr_disable ();
if (!list_empty (&sema->waiters))
thread_unblock (list_entry (list_pop_front (&sema->waiters),
struct thread, elem));
/* Wake up (unblock) the highest priority thread from the waiters list */
struct thread *t = NULL;
if (!list_empty (&sema->waiters))
{
t = list_entry (list_pop_front (&sema->waiters), struct thread, elem);
thread_unblock (t);
}
sema->value++;
intr_set_level (old_level);
/* If the unblocked thread has higher priority than the current running thread
then yield the CPU to the unblocked thread */
if (!intr_context() && t != NULL && t->priority > thread_get_priority ())
thread_yield ();
}
static void sema_test_helper (void *sema_);