runtime: print stack trace when "panic during panic"

Fixes bug 7145

R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/53970043

diff --git a/src/pkg/runtime/panic.c b/src/pkg/runtime/panic.c
index b60547ea10dec2786943938dc93dd2f25162c1eb..d85a8fefba7c9166d895bf5f5a5bd09646dcff94 100644 (file)
--- a/src/pkg/runtime/panic.c
+++ b/src/pkg/runtime/panic.c
@@ -371,7 +371,8 @@ runtime·startpanic(void)
                m->mcache = runtime·allocmcache();
        if(m->dying) {
                runtime·printf("panic during panic\n");
-               runtime·exit(3);
+               runtime·dopanic(0);
+               runtime·exit(3); // not reached
        }
        m->dying = 1;
        if(g != nil)