tryacquire q->lock in steal

8312d2c6 · Silas Boyd-Wickizer · 85bd3247 · 8312d2c6
--- a/sched.cc
+++ b/sched.cc
@@ -70,7 +70,8 @@ steal(void)
    // q->lock, scan for a process, drop q->lock, acquire p->lock,
    // and then check that it's still ok to steal p.
    steal = NULL;
-    acquire(&q->lock);
+    if (tryacquire(&q->lock) == 0)
+      continue;
    STAILQ_FOREACH(p, &q->q, runqlink) {
      if (p->state == RUNNABLE && !p->cpu_pin && 
          p->curcycles != 0 && p->curcycles > VICTIMAGE)