From 73df946d56c74384511a194dd01dbe099584fd1a Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 28 Apr 2024 15:14:23 +0200 Subject: Adding upstream version 1.16.10. Signed-off-by: Daniel Baumann --- src/os/signal/signal.go | 334 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 334 insertions(+) create mode 100644 src/os/signal/signal.go (limited to 'src/os/signal/signal.go') 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) +} -- cgit v1.2.3