Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 334 insertions, 0 deletions

diff --git a/src/os/signal/signal.go b/src/os/signal/signal.go
new file mode 100644
index 0000000..4250a7e
--- /dev/null
+++ b/src/os/signal/signal.go
@@ -0,0 +1,334 @@
+// Copyright 2012 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.
+
+package signal
+
+import (
+	"context"
+	"os"
+	"sync"
+)
+
+var handlers struct {
+	sync.Mutex
+	// Map a channel to the signals that should be sent to it.
+	m map[chan<- os.Signal]*handler
+	// Map a signal to the number of channels receiving it.
+	ref [numSig]int64
+	// Map channels to signals while the channel is being stopped.
+	// Not a map because entries live here only very briefly.
+	// We need a separate container because we need m to correspond to ref
+	// at all times, and we also need to keep track of the *handler
+	// value for a channel being stopped. See the Stop function.
+	stopping []stopping
+}
+
+type stopping struct {
+	c chan<- os.Signal
+	h *handler
+}
+
+type handler struct {
+	mask [(numSig + 31) / 32]uint32
+}
+
+func (h *handler) want(sig int) bool {
+	return (h.mask[sig/32]>>uint(sig&31))&1 != 0
+}
+
+func (h *handler) set(sig int) {
+	h.mask[sig/32] |= 1 << uint(sig&31)
+}
+
+func (h *handler) clear(sig int) {
+	h.mask[sig/32] &^= 1 << uint(sig&31)
+}
+
+// Stop relaying the signals, sigs, to any channels previously registered to
+// receive them and either reset the signal handlers to their original values
+// (action=disableSignal) or ignore the signals (action=ignoreSignal).
+func cancel(sigs []os.Signal, action func(int)) {
+	handlers.Lock()
+	defer handlers.Unlock()
+
+	remove := func(n int) {
+		var zerohandler handler
+
+		for c, h := range handlers.m {
+			if h.want(n) {
+				handlers.ref[n]--
+				h.clear(n)
+				if h.mask == zerohandler.mask {
+					delete(handlers.m, c)
+				}
+			}
+		}
+
+		action(n)
+	}
+
+	if len(sigs) == 0 {
+		for n := 0; n < numSig; n++ {
+			remove(n)
+		}
+	} else {
+		for _, s := range sigs {
+			remove(signum(s))
+		}
+	}
+}
+
+// Ignore causes the provided signals to be ignored. If they are received by
+// the program, nothing will happen. Ignore undoes the effect of any prior
+// calls to Notify for the provided signals.
+// If no signals are provided, all incoming signals will be ignored.
+func Ignore(sig ...os.Signal) {
+	cancel(sig, ignoreSignal)
+}
+
+// Ignored reports whether sig is currently ignored.
+func Ignored(sig os.Signal) bool {
+	sn := signum(sig)
+	return sn >= 0 && signalIgnored(sn)
+}
+
+var (
+	// watchSignalLoopOnce guards calling the conditionally
+	// initialized watchSignalLoop. If watchSignalLoop is non-nil,
+	// it will be run in a goroutine lazily once Notify is invoked.
+	// See Issue 21576.
+	watchSignalLoopOnce sync.Once
+	watchSignalLoop     func()
+)
+
+// Notify causes package signal to relay incoming signals to c.
+// If no signals are provided, all incoming signals will be relayed to c.
+// Otherwise, just the provided signals will.
+//
+// Package signal will not block sending to c: the caller must ensure
+// that c has sufficient buffer space to keep up with the expected
+// signal rate. For a channel used for notification of just one signal value,
+// a buffer of size 1 is sufficient.
+//
+// It is allowed to call Notify multiple times with the same channel:
+// each call expands the set of signals sent to that channel.
+// The only way to remove signals from the set is to call Stop.
+//
+// It is allowed to call Notify multiple times with different channels
+// and the same signals: each channel receives copies of incoming
+// signals independently.
+func Notify(c chan<- os.Signal, sig ...os.Signal) {
+	if c == nil {
+		panic("os/signal: Notify using nil channel")
+	}
+
+	handlers.Lock()
+	defer handlers.Unlock()
+
+	h := handlers.m[c]
+	if h == nil {
+		if handlers.m == nil {
+			handlers.m = make(map[chan<- os.Signal]*handler)
+		}
+		h = new(handler)
+		handlers.m[c] = h
+	}
+
+	add := func(n int) {
+		if n < 0 {
+			return
+		}
+		if !h.want(n) {
+			h.set(n)
+			if handlers.ref[n] == 0 {
+				enableSignal(n)
+
+				// The runtime requires that we enable a
+				// signal before starting the watcher.
+				watchSignalLoopOnce.Do(func() {
+					if watchSignalLoop != nil {
+						go watchSignalLoop()
+					}
+				})
+			}
+			handlers.ref[n]++
+		}
+	}
+
+	if len(sig) == 0 {
+		for n := 0; n < numSig; n++ {
+			add(n)
+		}
+	} else {
+		for _, s := range sig {
+			add(signum(s))
+		}
+	}
+}
+
+// Reset undoes the effect of any prior calls to Notify for the provided
+// signals.
+// If no signals are provided, all signal handlers will be reset.
+func Reset(sig ...os.Signal) {
+	cancel(sig, disableSignal)
+}
+
+// Stop causes package signal to stop relaying incoming signals to c.
+// It undoes the effect of all prior calls to Notify using c.
+// When Stop returns, it is guaranteed that c will receive no more signals.
+func Stop(c chan<- os.Signal) {
+	handlers.Lock()
+
+	h := handlers.m[c]
+	if h == nil {
+		handlers.Unlock()
+		return
+	}
+	delete(handlers.m, c)
+
+	for n := 0; n < numSig; n++ {
+		if h.want(n) {
+			handlers.ref[n]--
+			if handlers.ref[n] == 0 {
+				disableSignal(n)
+			}
+		}
+	}
+
+	// Signals will no longer be delivered to the channel.
+	// We want to avoid a race for a signal such as SIGINT:
+	// it should be either delivered to the channel,
+	// or the program should take the default action (that is, exit).
+	// To avoid the possibility that the signal is delivered,
+	// and the signal handler invoked, and then Stop deregisters
+	// the channel before the process function below has a chance
+	// to send it on the channel, put the channel on a list of
+	// channels being stopped and wait for signal delivery to
+	// quiesce before fully removing it.
+
+	handlers.stopping = append(handlers.stopping, stopping{c, h})
+
+	handlers.Unlock()
+
+	signalWaitUntilIdle()
+
+	handlers.Lock()
+
+	for i, s := range handlers.stopping {
+		if s.c == c {
+			handlers.stopping = append(handlers.stopping[:i], handlers.stopping[i+1:]...)
+			break
+		}
+	}
+
+	handlers.Unlock()
+}
+
+// Wait until there are no more signals waiting to be delivered.
+// Defined by the runtime package.
+func signalWaitUntilIdle()
+
+func process(sig os.Signal) {
+	n := signum(sig)
+	if n < 0 {
+		return
+	}
+
+	handlers.Lock()
+	defer handlers.Unlock()
+
+	for c, h := range handlers.m {
+		if h.want(n) {
+			// send but do not block for it
+			select {
+			case c <- sig:
+			default:
+			}
+		}
+	}
+
+	// Avoid the race mentioned in Stop.
+	for _, d := range handlers.stopping {
+		if d.h.want(n) {
+			select {
+			case d.c <- sig:
+			default:
+			}
+		}
+	}
+}
+
+// NotifyContext returns a copy of the parent context that is marked done
+// (its Done channel is closed) when one of the listed signals arrives,
+// when the returned stop function is called, or when the parent context's
+// Done channel is closed, whichever happens first.
+//
+// The stop function unregisters the signal behavior, which, like signal.Reset,
+// may restore the default behavior for a given signal. For example, the default
+// behavior of a Go program receiving os.Interrupt is to exit. Calling
+// NotifyContext(parent, os.Interrupt) will change the behavior to cancel
+// the returned context. Future interrupts received will not trigger the default
+// (exit) behavior until the returned stop function is called.
+//
+// The stop function releases resources associated with it, so code should
+// call stop as soon as the operations running in this Context complete and
+// signals no longer need to be diverted to the context.
+func NotifyContext(parent context.Context, signals ...os.Signal) (ctx context.Context, stop context.CancelFunc) {
+	ctx, cancel := context.WithCancel(parent)
+	c := &signalCtx{
+		Context: ctx,
+		cancel:  cancel,
+		signals: signals,
+	}
+	c.ch = make(chan os.Signal, 1)
+	Notify(c.ch, c.signals...)
+	if ctx.Err() == nil {
+		go func() {
+			select {
+			case <-c.ch:
+				c.cancel()
+			case <-c.Done():
+			}
+		}()
+	}
+	return c, c.stop
+}
+
+type signalCtx struct {
+	context.Context
+
+	cancel  context.CancelFunc
+	signals []os.Signal
+	ch      chan os.Signal
+}
+
+func (c *signalCtx) stop() {
+	c.cancel()
+	Stop(c.ch)
+}
+
+type stringer interface {
+	String() string
+}
+
+func (c *signalCtx) String() string {
+	var buf []byte
+	// We know that the type of c.Context is context.cancelCtx, and we know that the
+	// String method of cancelCtx returns a string that ends with ".WithCancel".
+	name := c.Context.(stringer).String()
+	name = name[:len(name)-len(".WithCancel")]
+	buf = append(buf, "signal.NotifyContext("+name...)
+	if len(c.signals) != 0 {
+		buf = append(buf, ", ["...)
+		for i, s := range c.signals {
+			buf = append(buf, s.String()...)
+			if i != len(c.signals)-1 {
+				buf = append(buf, ' ')
+			}
+		}
+		buf = append(buf, ']')
+	}
+	buf = append(buf, ')')
+	return string(buf)
+}