Cut the multiproduct_kati -> soong-ui-build dep.

This is done by moving SetupSignals() to its own little package.

There are a number of tiny little utility packages for soong_ui we might
be better of merging, but that's for another change (maybe)

Test: Presubmits.
Change-Id: I07b0ca98bfb8884ef4223d665e632183b9896a0d

ui/signal/Android.bp

@@ -0,0 +1,28 @@
+// Copyright 2021 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 {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+bootstrap_go_package {
+    name: "soong-ui-signal",
+    pkgPath: "android/soong/ui/signal",
+    srcs: [
+        "signal.go",
+    ],
+    deps: [
+        "soong-ui-logger",
+    ],
+}

ui/signal/signal.go

@@ -0,0 +1,94 @@
+// 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 signal
+
+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()
+		}
+	}
+}