libgo/go/time/internal_test.go

   1 // Copyright 2011 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package time
   6
   7 func init() {
   8         // force US/Pacific for time zone tests
   9         ForceUSPacificForTesting()
  10 }
  11
  12 var Interrupt = interrupt
  13 var DaysIn = daysIn
  14
  15 func empty(arg interface{}, seq uintptr) {}
  16
  17 // Test that a runtimeTimer with a duration so large it overflows
  18 // does not cause other timers to hang.
  19 //
  20 // This test has to be in internal_test.go since it fiddles with
  21 // unexported data structures.
  22 func CheckRuntimeTimerOverflow() {
  23         // We manually create a runtimeTimer to bypass the overflow
  24         // detection logic in NewTimer: we're testing the underlying
  25         // runtime.addtimer function.
  26         r := &runtimeTimer{
  27                 when: runtimeNano() + (1<<63 - 1),
  28                 f:    empty,
  29                 arg:  nil,
  30         }
  31         startTimer(r)
  32
  33         // Start a goroutine that should send on t.C right away.
  34         t := NewTimer(1)
  35
  36         defer func() {
  37                 // Subsequent tests won't work correctly if we don't stop the
  38                 // overflow timer and kick the timer proc back into service.
  39                 //
  40                 // The timer proc is now sleeping and can only be awoken by
  41                 // adding a timer to the *beginning* of the heap. We can't
  42                 // wake it up by calling NewTimer since other tests may have
  43                 // left timers running that should have expired before ours.
  44                 // Instead we zero the overflow timer duration and start it
  45                 // once more.
  46                 stopTimer(r)
  47                 t.Stop()
  48                 r.when = 0
  49                 startTimer(r)
  50         }()
  51
  52         // If the test fails, we will hang here until the timeout in the testing package
  53         // fires, which is 10 minutes. It would be nice to catch the problem sooner,
  54         // but there is no reliable way to guarantee that timerproc schedules without
  55         // doing something involving timerproc itself. Previous failed attempts have
  56         // tried calling runtime.Gosched and runtime.GC, but neither is reliable.
  57         // So we fall back to hope: We hope we don't hang here.
  58         <-t.C
  59 }