misc/android: serialize adb commands on android emulators

Android emulator builders are soon to join the trybot set. To avoid
flaky runs, work around a longstanding adb bug where concurrent adb
commands sometimes fail.

I haven't seen the problem on actual devices until recently. It seems
that the recently added "adb wait-for-device" can introduce flakyness
with errors such as:

adb: error: failed to get feature set: protocol fault (couldn't read status): Connection reset by peer

Instead of working around that, give up and serialize use of adb
everywhere.

Fixes #23795
Updates #23824

Change-Id: If347c9981fa32ff8a1e14b7454f122ef682450a6
Reviewed-on: https://go-review.googlesource.com/c/163625
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/misc/android/go_android_exec.go b/misc/android/go_android_exec.go
index 1a8ae7070e38fbc3e75499db5f5ef8e5ac29b1ec..0055fb832af763777db66c2a724aca81930c0ae0 100644 (file)
--- a/misc/android/go_android_exec.go
+++ b/misc/android/go_android_exec.go
@@ -60,6 +60,19 @@ func main() {
        log.SetFlags(0)
        log.SetPrefix("go_android_exec: ")
 
+       // Concurrent use of adb is flaky, so serialize adb commands.
+       // See https://github.com/golang/go/issues/23795 or
+       // https://issuetracker.google.com/issues/73230216.
+       lockPath := filepath.Join(os.TempDir(), "go_android_exec-adb-lock")
+       lock, err := os.OpenFile(lockPath, os.O_CREATE|os.O_RDWR, 0666)
+       if err != nil {
+               log.Fatal(err)
+       }
+       defer lock.Close()
+       if err := syscall.Flock(int(lock.Fd()), syscall.LOCK_EX); err != nil {
+               log.Fatal(err)
+       }
+
        // In case we're booting a device or emulator alongside androidtest.bash
        // wait for it to be ready. adb wait-for-device is not enough, we have to
        // wait for sys.boot_completed.
@@ -87,15 +100,7 @@ func main() {
        // E.g. template.test from the {html,text}/template packages.
        binName := fmt.Sprintf("%s-%d", filepath.Base(os.Args[1]), os.Getpid())
        deviceBin := fmt.Sprintf("%s/%s", deviceGotmp, binName)
-
-       // The push of the binary happens in parallel with other tests.
-       // Unfortunately, a simultaneous call to adb shell hold open
-       // file descriptors, so it is necessary to push then move to
-       // avoid a "text file busy" error on execution.
-       // https://code.google.com/p/android/issues/detail?id=65857
-       run("push", os.Args[1], deviceBin+"-tmp")
-       run("shell", "cp '"+deviceBin+"-tmp' '"+deviceBin+"'")
-       run("shell", "rm '"+deviceBin+"-tmp'")
+       run("push", os.Args[1], deviceBin)
 
        // Forward SIGQUIT from the go command to show backtraces from
        // the binary instead of from this wrapper.