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