libgo: Update to weekly.2012-03-27 aka go1 release.

From-SVN: r186029

1 files changed, 19 insertions, 0 deletions

diff --git a/libgo/runtime/proc.c b/libgo/runtime/proc.c
index dbcfa0f..9ad9f96 100644
--- a/libgo/runtime/proc.c
+++ b/libgo/runtime/proc.c
@@ -448,6 +448,11 @@ runtime_main(void)
 	// roots.
 	mstats.enablegc = 1;
 
+	// The deadlock detection has false negatives.
+	// Let scvg start up, to eliminate the false negative
+	// for the trivial program func main() { select{} }.
+	runtime_gosched();
+
 	main_main();
 	runtime_exit(0);
 	for(;;)
@@ -795,6 +800,20 @@ top:
 	}
 
 	// Look for deadlock situation.
+	// There is a race with the scavenger that causes false negatives:
+	// if the scavenger is just starting, then we have
+	//	scvg != nil && grunning == 0 && gwait == 0
+	// and we do not detect a deadlock.  It is possible that we should
+	// add that case to the if statement here, but it is too close to Go 1
+	// to make such a subtle change.  Instead, we work around the
+	// false negative in trivial programs by calling runtime.gosched
+	// from the main goroutine just before main.main.
+	// See runtime_main above.
+	//
+	// On a related note, it is also possible that the scvg == nil case is
+	// wrong and should include gwait, but that does not happen in
+	// standard Go programs, which all start the scavenger.
+	//
 	if((scvg == nil && runtime_sched.grunning == 0) ||
 	   (scvg != nil && runtime_sched.grunning == 1 && runtime_sched.gwait == 0 &&
 	    (scvg->status == Grunning || scvg->status == Gsyscall))) {