// Copyright 2017 Google Inc. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package build
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import (
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"os"
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"os/signal"
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"runtime/debug"
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"syscall"
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"android/soong/ui/logger"
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"time"
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)
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// SetupSignals sets up signal handling to ensure all of our subprocesses are killed and that
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// our log/trace buffers are flushed to disk.
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//
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// All of our subprocesses are in the same process group, so they'll receive a SIGINT at the
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// same time we do. Most of the time this means we just need to ignore the signal and we'll
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// just see errors from all of our subprocesses. But in case that fails, when we get a signal:
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//
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// 1. Wait two seconds to exit normally.
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// 2. Call cancel() which is normally the cancellation of a Context. This will send a SIGKILL
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// to any subprocesses attached to that context.
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// 3. Wait two seconds to exit normally.
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// 4. Call cleanup() to close the log/trace buffers, then panic.
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// 5. If another two seconds passes (if cleanup got stuck, etc), then panic.
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//
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func SetupSignals(log logger.Logger, cancel, cleanup func()) {
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signals := make(chan os.Signal, 5)
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signal.Notify(signals, os.Interrupt, syscall.SIGHUP, syscall.SIGQUIT, syscall.SIGTERM)
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go handleSignals(signals, log, cancel, cleanup)
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}
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func handleSignals(signals chan os.Signal, log logger.Logger, cancel, cleanup func()) {
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var timeouts int
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var timeout <-chan time.Time
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handleTimeout := func() {
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timeouts += 1
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switch timeouts {
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case 1:
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// Things didn't exit cleanly, cancel our ctx (SIGKILL to subprocesses)
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// Do this asynchronously to ensure it won't block and prevent us from
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// taking more drastic measures.
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log.Println("Still alive, killing subprocesses...")
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go cancel()
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case 2:
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// Cancel didn't work. Try to run cleanup manually, then we'll panic
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// at the next timer whether it finished or not.
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log.Println("Still alive, cleaning up...")
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// Get all stacktraces to see what was stuck
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debug.SetTraceback("all")
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go func() {
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defer log.Panicln("Timed out exiting...")
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cleanup()
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}()
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default:
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// In case cleanup() deadlocks, the next tick will panic.
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log.Panicln("Got signal, but timed out exiting...")
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}
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}
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for {
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select {
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case s := <-signals:
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log.Println("Got signal:", s)
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// Another signal triggers our next timeout handler early
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if timeout != nil {
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handleTimeout()
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}
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// Wait 2 seconds for everything to exit cleanly.
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timeout = time.Tick(time.Second * 2)
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case <-timeout:
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handleTimeout()
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}
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}
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}
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