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author | Ian Lance Taylor <iant@golang.org> | 2020-10-27 16:09:40 -0700 |
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committer | Ian Lance Taylor <iant@golang.org> | 2020-10-28 01:03:23 +0000 |
commit | 368c40116434532dc0b53b72fa04788ca6742898 (patch) | |
tree | d3a6b5bc4816eb17ed181df850f1671d8629fffb /src/runtime/testdata | |
parent | 94f3762462a999bfc5491c8d1b892110651e23d6 (diff) | |
download | go-368c40116434532dc0b53b72fa04788ca6742898.tar.gz go-368c40116434532dc0b53b72fa04788ca6742898.zip |
runtime: block signals in needm before allocating M
Otherwise, if a signal occurs just after we allocated the M,
we can deadlock if the signal handler needs to allocate an M
itself.
Fixes #42207
Change-Id: I76f44547f419e8b1c14cbf49bf602c6e645d8c14
Reviewed-on: https://go-review.googlesource.com/c/go/+/265759
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Diffstat (limited to 'src/runtime/testdata')
-rw-r--r-- | src/runtime/testdata/testprogcgo/needmdeadlock.go | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/src/runtime/testdata/testprogcgo/needmdeadlock.go b/src/runtime/testdata/testprogcgo/needmdeadlock.go new file mode 100644 index 0000000000..5a9c359006 --- /dev/null +++ b/src/runtime/testdata/testprogcgo/needmdeadlock.go @@ -0,0 +1,95 @@ +// 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 + +// 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") +} |