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runtime/cgo: fix deadlock involving signals on darwin

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sigprocmask() is process-wide on darwin, so two concurrent
libcgo_sys_thread_start() can result in all signals permanently
blocked, which in particular blocks handling of nil derefs.
Fixes #4833.

R=golang-dev, dave, rsc
CC=golang-dev
https://golang.org/cl/7324058
This commit is contained in:
Dmitriy Vyukov 2013-02-25 16:36:29 -05:00 committed by Russ Cox
parent 052d845c5c
commit 4eb7ba743d
3 changed files with 77 additions and 4 deletions
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4
src/pkg/runtime/cgo/gcc_darwin_386.c
View File

@ -127,14 +127,14 @@ libcgo_sys_thread_start(ThreadStart *ts)
int err;
sigfillset(&ign);
sigprocmask(SIG_SETMASK, &ign, &oset);
pthread_sigmask(SIG_SETMASK, &ign, &oset);
pthread_attr_init(&attr);
pthread_attr_getstacksize(&attr, &size);
ts->g->stackguard = size;
err = pthread_create(&p, &attr, threadentry, ts);
sigprocmask(SIG_SETMASK, &oset, nil);
pthread_sigmask(SIG_SETMASK, &oset, nil);
if (err != 0) {
fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));

4
src/pkg/runtime/cgo/gcc_darwin_amd64.c
View File

@ -97,14 +97,14 @@ libcgo_sys_thread_start(ThreadStart *ts)
int err;
sigfillset(&ign);
sigprocmask(SIG_SETMASK, &ign, &oset);
pthread_sigmask(SIG_SETMASK, &ign, &oset);
pthread_attr_init(&attr);
pthread_attr_getstacksize(&attr, &size);
ts->g->stackguard = size;
err = pthread_create(&p, &attr, threadentry, ts);
sigprocmask(SIG_SETMASK, &oset, nil);
pthread_sigmask(SIG_SETMASK, &oset, nil);
if (err != 0) {
fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));

73
src/pkg/runtime/crash_test.go
View File

@ -99,6 +99,14 @@ func TestLockedDeadlock2(t *testing.T) {
testDeadlock(t, lockedDeadlockSource2)
}
func TestCgoSignalDeadlock(t *testing.T) {
got := executeTest(t, cgoSignalDeadlockSource, nil)
want := "OK\n"
if got != want {
t.Fatalf("expected %q, but got %q", want, got)
}
}
const crashSource = `
package main
@ -183,3 +191,68 @@ func main() {
select {}
}
`
const cgoSignalDeadlockSource = `
package main
import "C"
import (
"fmt"
"runtime"
"time"
)
func main() {
runtime.GOMAXPROCS(100)
ping := make(chan bool)
go func() {
for i := 0; ; i++ {
runtime.Gosched()
select {
case done := <-ping:
if done {
ping <- true
return
}
ping <- true
default:
}
func() {
defer func() {
recover()
}()
var s *string
*s = ""
}()
}
}()
time.Sleep(time.Millisecond)
for i := 0; i < 64; i++ {
go func() {
runtime.LockOSThread()
select {}
}()
go func() {
runtime.LockOSThread()
select {}
}()
time.Sleep(time.Millisecond)
ping <- false
select {
case <-ping:
case <-time.After(time.Second):
fmt.Printf("HANG\n")
return
}
}
ping <- true
select {
case <-ping:
case <-time.After(time.Second):
fmt.Printf("HANG\n")
return
}
fmt.Printf("OK\n")
}
`