testing: add -test.timeout option.

Since Go code can deadlock, this lets a testsuite driver set a
time limit for the test to run.  This is simple but imperfect,
in that it only catches deadlocks in Go code, not in the
runtime scheduler.

R=r, rsc, iant2
CC=golang-dev
https://golang.org/cl/4326048

src/Make.pkg

@@ -61,7 +61,7 @@ test:
 	gotest
 
 testshort:
-	gotest -test.short
+	gotest -test.short -test.timeout=60
 
 bench:
 	gotest -test.bench=. -test.run="Do not run tests"

src/cmd/gotest/doc.go

@@ -82,11 +82,15 @@ collection.
 Use -test.run or -test.bench to limit profiling to a particular test
 or benchmark.
 
-The -test.short package tells long-running tests to shorten their run
+The -test.short flag tells long-running tests to shorten their run
 time.  It is off by default but set by all.bash so installations of
 the Go tree can do a sanity check but not spend time running
 exhaustive tests.
 
+The -test.timeout flag sets a timeout for the test in seconds.  If the
+test runs for longer than that, it will panic, dumping a stack trace
+of all existing goroutines.
+
 For convenience, each of these -test.X flags of the test binary is
 also available as the flag -X in gotest itself.  Flags not listed here
 are unaffected.  For instance, the command

src/cmd/gotest/flag.go

@@ -28,6 +28,7 @@ var usageMessage = `Usage of %s:
   -memprofilerate=0: passes -test.memprofilerate to test
   -run="": passes -test.run to test
   -short=false: passes -test.short to test
+  -timeout=0: passes -test.timeout to test
   -v=false: passes -test.v to test
 `
 
@@ -60,6 +61,7 @@ var flagDefn = []*flagSpec{
 	&flagSpec{name: "memprofilerate", passToTest: true},
 	&flagSpec{name: "run", passToTest: true},
 	&flagSpec{name: "short", isBool: true, passToTest: true},
+	&flagSpec{name: "timeout", passToTest: true},
 	&flagSpec{name: "v", isBool: true, passToTest: true},
 }
 

src/pkg/testing/testing.go

@@ -61,6 +61,7 @@ var (
 	memProfile     = flag.String("test.memprofile", "", "write a memory profile to the named file after execution")
 	memProfileRate = flag.Int("test.memprofilerate", 0, "if >=0, sets runtime.MemProfileRate")
 	cpuProfile     = flag.String("test.cpuprofile", "", "write a cpu profile to the named file during execution")
+	timeout        = flag.Int64("test.timeout", 0, "if > 0, sets time limit for tests in seconds")
 )
 
 // Short reports whether the -test.short flag is set.
@@ -158,7 +159,9 @@ func Main(matchString func(pat, str string) (bool, os.Error), tests []InternalTe
 	flag.Parse()
 
 	before()
+	startAlarm()
 	RunTests(matchString, tests)
+	stopAlarm()
 	RunBenchmarks(matchString, benchmarks)
 	after()
 }
@@ -241,3 +244,24 @@ func after() {
 		f.Close()
 	}
 }
+
+var timer *time.Timer
+
+// startAlarm starts an alarm if requested.
+func startAlarm() {
+	if *timeout > 0 {
+		timer = time.AfterFunc(*timeout*1e9, alarm)
+	}
+}
+
+// stopAlarm turns off the alarm.
+func stopAlarm() {
+	if *timeout > 0 {
+		timer.Stop()
+	}
+}
+
+// alarm is called if the timeout expires.
+func alarm() {
+	panic("test timed out")
+}