core: thread: return 0 from sem_down() if we didn't have to wait

Return 0 from sem_down if we passed right through the assembly code.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/core/thread/sem_asm.S b/core/thread/sem_asm.S
index 2b3014f..ce67471 100644 (file)
--- a/core/thread/sem_asm.S
+++ b/core/thread/sem_asm.S
@@ -3,6 +3,7 @@
 sem_down:
        decl    (%eax)
        js      __sem_down_slow
+       xorl    %eax, %eax
        ret
        .size   sem_down, .-sem_down