runtime: crash on SI_USER SigPanic signal

Clean up the code a little bit to make it clearer:

Don't check throwsplit for a SI_USER signal.

If throwsplit is set for a SigPanic signal, always throw;
discard any other flags.

Fixes #36420

Change-Id: Ic9dcd1108603d241f71c040504dfdc6e528f9767
Reviewed-on: https://go-review.googlesource.com/c/go/+/228900
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

1 files changed, 60 insertions, 0 deletions

diff --git a/src/runtime/testdata/testprogcgo/segv.go b/src/runtime/testdata/testprogcgo/segv.go
new file mode 100644
index 0000000000..77e75f276a
--- /dev/null
+++ b/src/runtime/testdata/testprogcgo/segv.go
@@ -0,0 +1,60 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !plan9,!windows
+
+package main
+
+// static void nop() {}
+import "C"
+
+import (
+	"sync"
+	"syscall"
+)
+
+func init() {
+	register("Segv", Segv)
+	register("SegvInCgo", SegvInCgo)
+}
+
+var Sum int
+
+func Segv() {
+	c := make(chan bool)
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		close(c)
+		for i := 0; i < 10000; i++ {
+			Sum += i
+		}
+	}()
+
+	<-c
+
+	syscall.Kill(syscall.Getpid(), syscall.SIGSEGV)
+
+	wg.Wait()
+}
+
+func SegvInCgo() {
+	c := make(chan bool)
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		close(c)
+		for i := 0; i < 10000; i++ {
+			C.nop()
+		}
+	}()
+
+	<-c
+
+	syscall.Kill(syscall.Getpid(), syscall.SIGSEGV)
+
+	wg.Wait()
+}