shithub: mc

Download patch

ref: f3c06e95f5a15488e1a99a272c3f0123dc5516a7
parent: 0fd71287884cec6e5d3a34307970a354ae99fc92
author: Ori Bernstein <ori@eigenstate.org>
date: Wed Jan 6 07:27:22 EST 2016 

Fix mutexes.

	Turns out atomic increments weren't returning the old value. Oops.


--- a/lib/thread/atomic-impl+plan9-x64.s
+++ b/lib/thread/atomic-impl+plan9-x64.s
@@ -20,12 +20,15 @@
 
 TEXT thread$xadd32+0(SB),1,$0
 	LOCK; XADDL	SI, (DI)
+	MOVL	SI, AX
 	RET
 TEXT thread$xadd64+0(SB),1,$0
 	LOCK; XADDQ	SI, (DI)
+	MOVQ	SI, AX
 	RET
 TEXT thread$xaddp+0(SB),1,$0
 	LOCK; XADDQ	SI, (DI)
+	MOVQ	SI, AX
 	RET
 
 TEXT thread$xsub32+0(SB),1,$0
--- a/lib/thread/mutex+plan9.myr
+++ b/lib/thread/mutex+plan9.myr
@@ -18,11 +18,12 @@
 ;;
 
 const mkmtx = {
-	-> [._state = 0]
+	-> [._state = 0, ._sem=0]
 }
 
 const mtxlock = {mtx
-	if xadd(&mtx._state, 1) == 1
+	/* if the old value was 0, we aren't contended */
+	if xadd(&mtx._state, 1) == 0
 		-> void
 	;;
 	
@@ -37,8 +38,10 @@
 
 	
 const mtxunlock = {mtx
-	if xadd(&mtx._state, -1) == 0
+	/* if we were the only thread waiting on the lock, there was no contention */
+	if xadd(&mtx._state, -1) == 1
 		-> void
 	;;
+
 	sys.semrelease(&mtx._sem, 1)
 }
--- a/lib/thread/test/mutex.myr
+++ b/lib/thread/test/mutex.myr
@@ -29,6 +29,5 @@
 		val++
 		thread.mtxunlock(&mtx)
 	;;
-	std.write(1, "done\n")
 	thread.xadd(&done, 1)
 }