1// Copyright 2017 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:build unix
6
7package runtime
8
9import "unsafe"
10
11var NonblockingPipe = nonblockingPipe
12var Fcntl = fcntl
13var Closeonexec = closeonexec
14
15func sigismember(mask *sigset, i int) bool {
16	clear := *mask
17	sigdelset(&clear, i)
18	return clear != *mask
19}
20
21func Sigisblocked(i int) bool {
22	var sigmask sigset
23	sigprocmask(_SIG_SETMASK, nil, &sigmask)
24	return sigismember(&sigmask, i)
25}
26
27type M = m
28
29var waitForSigusr1 struct {
30	rdpipe int32
31	wrpipe int32
32	mID    int64
33}
34
35// WaitForSigusr1 blocks until a SIGUSR1 is received. It calls ready
36// when it is set up to receive SIGUSR1. The ready function should
37// cause a SIGUSR1 to be sent. The r and w arguments are a pipe that
38// the signal handler can use to report when the signal is received.
39//
40// Once SIGUSR1 is received, it returns the ID of the current M and
41// the ID of the M the SIGUSR1 was received on. If the caller writes
42// a non-zero byte to w, WaitForSigusr1 returns immediately with -1, -1.
43func WaitForSigusr1(r, w int32, ready func(mp *M)) (int64, int64) {
44	lockOSThread()
45	// Make sure we can receive SIGUSR1.
46	unblocksig(_SIGUSR1)
47
48	waitForSigusr1.rdpipe = r
49	waitForSigusr1.wrpipe = w
50
51	mp := getg().m
52	testSigusr1 = waitForSigusr1Callback
53	ready(mp)
54
55	// Wait for the signal. We use a pipe rather than a note
56	// because write is always async-signal-safe.
57	entersyscallblock()
58	var b byte
59	read(waitForSigusr1.rdpipe, noescape(unsafe.Pointer(&b)), 1)
60	exitsyscall()
61
62	gotM := waitForSigusr1.mID
63	testSigusr1 = nil
64
65	unlockOSThread()
66
67	if b != 0 {
68		// timeout signal from caller
69		return -1, -1
70	}
71	return mp.id, gotM
72}
73
74// waitForSigusr1Callback is called from the signal handler during
75// WaitForSigusr1. It must not have write barriers because there may
76// not be a P.
77//
78//go:nowritebarrierrec
79func waitForSigusr1Callback(gp *g) bool {
80	if gp == nil || gp.m == nil {
81		waitForSigusr1.mID = -1
82	} else {
83		waitForSigusr1.mID = gp.m.id
84	}
85	b := byte(0)
86	write(uintptr(waitForSigusr1.wrpipe), noescape(unsafe.Pointer(&b)), 1)
87	return true
88}
89
90// SendSigusr1 sends SIGUSR1 to mp.
91func SendSigusr1(mp *M) {
92	signalM(mp, _SIGUSR1)
93}
94
95const (
96	O_WRONLY = _O_WRONLY
97	O_CREAT  = _O_CREAT
98	O_TRUNC  = _O_TRUNC
99)
100