sync with sources

Reference: /n/atom/patch/applied/oventibits
Date: Thu Mar 20 15:31:23 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/liboventi/plan9-thread.c	Thu Mar 20 15:30:44 2014
+++ /sys/src/liboventi/plan9-thread.c	Thu Mar 20 15:30:44 2014
@@ -25,6 +25,7 @@
 	int readers;		/* number writering read lock */
 	Thread *qfirst;
 	Thread *qlast;
+	uintptr	pc;
 };
 
 struct VtRendez {
@@ -170,7 +171,7 @@
 }
 
 /*
- * RSC: I think the test is backward.  Let's see who uses it. 
+ * RSC: I think the test is backward.  Let's see who uses it.
  *
 void
 vtLockInit(VtLock **p)
@@ -238,6 +239,7 @@
 	Thread *t;
 
 	lock(&p->lk);
+	p->pc = getcallerpc(&p);
 	t = *vtRock;
 	if(p->writer == nil && p->readers == 0) {
 		p->writer = t;
@@ -316,7 +318,7 @@
 	 * venti currently has code that assumes lock can be passed between threads :-)
  	 * assert(p->writer == *vtRock);
 	 */
- 	assert(p->writer != nil);   
+ 	assert(p->writer != nil);
 	assert(p->readers == 0);
 	t = p->qfirst;
 	if(t == nil) {
@@ -328,6 +330,7 @@
 		p->qfirst = t->next;
 		p->writer = t;
 		unlock(&p->lk);
+
 		threadWakeup(t);
 		return;
 	}
@@ -337,6 +340,7 @@
 		tt = t;
 		t = t->next;
 		p->readers++;
+
 		threadWakeup(tt);
 	}
 	p->qfirst = t;
@@ -357,7 +361,7 @@
 		return;
 	}
 	assert(t->state == QueuingW);
-	
+
 	p->qfirst = t->next;
 	p->writer = t;
 	unlock(&p->lk);
@@ -421,7 +425,7 @@
 	 * put on front so guys that have been waiting will not get starved
 	 */
 	p = q->lk;
-	lock(&p->lk);	
+	lock(&p->lk);
 	/*
 	 * venti currently has code that assumes lock can be passed between threads :-)
  	 * assert(p->writer == *vtRock);
@@ -447,7 +451,7 @@
 vtWakeupAll(VtRendez *q)
 {
 	int i;
-	
+
 	for(i=0; vtWakeup(q); i++)
 		;
 	return i;