In sem_forkhook(), don't attempt to generate a copy of the process semaphore

list on fork() if the process doesn't actually have references to any
semaphores.  This avoids extra work, as well as potentially asking to
allocate storage for 0 references.

Found by:	avatar
MFC after:	1 week

1 files changed, 4 insertions, 0 deletions

diff --git a/sys/kern/uipc_sem.c b/sys/kern/uipc_sem.c
index 394b6cb..de012b6 100644
--- a/sys/kern/uipc_sem.c
+++ b/sys/kern/uipc_sem.c
@@ -915,6 +915,10 @@ sem_forkhook(arg, p1, p2, flags)
 
 	mtx_lock(&sem_lock);
 	count = sem_count_proc(p1);
+	if (count == 0) {
+		mtx_unlock(&sem_lock);
+		return;
+	}
 race_lost:
 	mtx_assert(&sem_lock, MA_OWNED);
 	mtx_unlock(&sem_lock);