stack overflow debugging and fix.

  * in 6l, -K already meant check for stack underflow.
    add -KK to mean double-check stack overflows
    even in nosplit functions.

  * comment out print locks; they deadlock too easily
     but are still useful to put back for special occasions.

  * let runcgo assembly switch to scheduler stack
    without involving scheduler directly.  because runcgo
    gets called from matchmg, it is too hard to keep it
    from being called on other stacks.

R=r
DELTA=94  (65 added, 18 deleted, 11 changed)
OCL=35591
CL=35604

1 files changed, 1 insertions, 4 deletions

diff --git a/src/pkg/runtime/cgocall.c b/src/pkg/runtime/cgocall.c
index a47560395..70382ceee 100644
--- a/src/pkg/runtime/cgocall.c
+++ b/src/pkg/runtime/cgocall.c
@@ -25,10 +25,7 @@ cgocall(void (*fn)(void*), void *arg)
 	 * foreign code.
 	 */
 	sys·entersyscall();
-	g->cgofn = fn;
-	g->cgoarg = arg;
-	g->status = Gcgocall;
-	gosched();
+	runcgo(fn, arg);
 	sys·exitsyscall();
 	return;
 }