unsafe to continue SLIST_FOREACH in scheduler after letting go of runq->lock

b6d8d9ad · Nickolai Zeldovich · 971c3376 · b6d8d9ad
--- a/proc.c
+++ b/proc.c
@@ -425,11 +425,14 @@ scheduler(void)
      proc = 0;
      release(&p->lock);
-      acquire(&runq->lock);
+      // Cannot loop: process may have been stolen, run_next is another runq.
+      break;
    }
-    release(&runq->lock);
-    steal();
+    if(p==0) {
+      release(&runq->lock);
+      steal();
+    }
  }
 }