runtime: make sure to remove open-coded defer entries in all cases after a recover

We add entries to the defer list at panic/goexit time on-the-fly for
frames with open-coded defers. We do this so that we can correctly
process open-coded defers and non-open-coded defers in the correct order
during panics/goexits. But we need to remove entries for open-coded
defers from the defer list when there is a recover, since those entries
may never get removed otherwise and will get stale, since their
corresponding defers may now be processed normally (inline).

This bug here is that we were only removing higher-up stale entries
during a recover if all defers in the current frame were done. But we
could have more defers in the current frame (as the new test case
shows). In this case, we need to leave the current defer entry around
for use by deferreturn, but still remove any stale entries further along
the chain.

For bug 43921, simple change that we should abort the removal loop for
any defer entry that is started (i.e. in process by a still
not-recovered outer panic), even if it is not an open-coded defer.

This change does not fix bug 43920, which looks to be a more complex fix.

Fixes #43882
Fixes #43921

Change-Id: Ie05b2fa26973aa26b25c8899a2abc916090ee4f5
Reviewed-on: https://go-review.googlesource.com/c/go/+/286712
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/runtime/crash_test.go b/src/runtime/crash_test.go
index 58ad4f3eba..e5bd7973b7 100644
--- a/src/runtime/crash_test.go
+++ b/src/runtime/crash_test.go
@@ -294,6 +294,18 @@ func TestRecursivePanic4(t *testing.T) {
 
 }
 
+func TestRecursivePanic5(t *testing.T) {
+	output := runTestProg(t, "testprog", "RecursivePanic5")
+	want := `first panic
+second panic
+panic: third panic
+`
+	if !strings.HasPrefix(output, want) {
+		t.Fatalf("output does not start with %q:\n%s", want, output)
+	}
+
+}
+
 func TestGoexitCrash(t *testing.T) {
 	// External linking brings in cgo, causing deadlock detection not working.
 	testenv.MustInternalLink(t)