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-rw-r--r--src/runtime/testdata/testprogcgo/needmdeadlock.go96
1 files changed, 96 insertions, 0 deletions
diff --git a/src/runtime/testdata/testprogcgo/needmdeadlock.go b/src/runtime/testdata/testprogcgo/needmdeadlock.go
new file mode 100644
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--- /dev/null
+++ b/src/runtime/testdata/testprogcgo/needmdeadlock.go
@@ -0,0 +1,96 @@
+// 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.
+
+//go:build !plan9 && !windows
+// +build !plan9,!windows
+
+package main
+
+// This is for issue #42207.
+// During a call to needm we could get a SIGCHLD signal
+// which would itself call needm, causing a deadlock.
+
+/*
+#include <signal.h>
+#include <pthread.h>
+#include <sched.h>
+#include <unistd.h>
+
+extern void GoNeedM();
+
+#define SIGNALERS 10
+
+static void* needmSignalThread(void* p) {
+ pthread_t* pt = (pthread_t*)(p);
+ int i;
+
+ for (i = 0; i < 100; i++) {
+ if (pthread_kill(*pt, SIGCHLD) < 0) {
+ return NULL;
+ }
+ usleep(1);
+ }
+ return NULL;
+}
+
+// We don't need many calls, as the deadlock is only likely
+// to occur the first couple of times that needm is called.
+// After that there will likely be an extra M available.
+#define CALLS 10
+
+static void* needmCallbackThread(void* p) {
+ int i;
+
+ for (i = 0; i < SIGNALERS; i++) {
+ sched_yield(); // Help the signal threads get started.
+ }
+ for (i = 0; i < CALLS; i++) {
+ GoNeedM();
+ }
+ return NULL;
+}
+
+static void runNeedmSignalThread() {
+ int i;
+ pthread_t caller;
+ pthread_t s[SIGNALERS];
+
+ pthread_create(&caller, NULL, needmCallbackThread, NULL);
+ for (i = 0; i < SIGNALERS; i++) {
+ pthread_create(&s[i], NULL, needmSignalThread, &caller);
+ }
+ for (i = 0; i < SIGNALERS; i++) {
+ pthread_join(s[i], NULL);
+ }
+ pthread_join(caller, NULL);
+}
+*/
+import "C"
+
+import (
+ "fmt"
+ "os"
+ "time"
+)
+
+func init() {
+ register("NeedmDeadlock", NeedmDeadlock)
+}
+
+//export GoNeedM
+func GoNeedM() {
+}
+
+func NeedmDeadlock() {
+ // The failure symptom is that the program hangs because of a
+ // deadlock in needm, so set an alarm.
+ go func() {
+ time.Sleep(5 * time.Second)
+ fmt.Println("Hung for 5 seconds")
+ os.Exit(1)
+ }()
+
+ C.runNeedmSignalThread()
+ fmt.Println("OK")
+}