libgo/go/runtime/export_unix_test.go

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