test/fixedbugs/issue9110.go

   1 // run
   2
   3 // Copyright 2014 The Go Authors.  All rights reserved.
   4 // Use of this source code is governed by a BSD-style
   5 // license that can be found in the LICENSE file.
   6
   7 // Scenario that used to leak arbitrarily many SudoG structs.
   8 // See golang.org/issue/9110.
   9
  10 package main
  11
  12 import (
  13         "runtime"
  14         "runtime/debug"
  15         "sync"
  16         "time"
  17 )
  18
  19 func main() {
  20         runtime.GOMAXPROCS(1)
  21         debug.SetGCPercent(1000000) // only GC when we ask for GC
  22
  23         var stats, stats1, stats2 runtime.MemStats
  24
  25         release := func() {}
  26         for i := 0; i < 20; i++ {
  27                 if i == 10 {
  28                         // Should be warmed up by now.
  29                         runtime.ReadMemStats(&stats1)
  30                 }
  31
  32                 c := make(chan int)
  33                 for i := 0; i < 10; i++ {
  34                         go func() {
  35                                 select {
  36                                 case <-c:
  37                                 case <-c:
  38                                 case <-c:
  39                                 }
  40                         }()
  41                 }
  42                 time.Sleep(1 * time.Millisecond)
  43                 release()
  44
  45                 close(c) // let select put its sudog's into the cache
  46                 time.Sleep(1 * time.Millisecond)
  47
  48                 // pick up top sudog
  49                 var cond1 sync.Cond
  50                 var mu1 sync.Mutex
  51                 cond1.L = &mu1
  52                 go func() {
  53                         mu1.Lock()
  54                         cond1.Wait()
  55                         mu1.Unlock()
  56                 }()
  57                 time.Sleep(1 * time.Millisecond)
  58
  59                 // pick up next sudog
  60                 var cond2 sync.Cond
  61                 var mu2 sync.Mutex
  62                 cond2.L = &mu2
  63                 go func() {
  64                         mu2.Lock()
  65                         cond2.Wait()
  66                         mu2.Unlock()
  67                 }()
  68                 time.Sleep(1 * time.Millisecond)
  69
  70                 // put top sudog back
  71                 cond1.Broadcast()
  72                 time.Sleep(1 * time.Millisecond)
  73
  74                 // drop cache on floor
  75                 runtime.GC()
  76
  77                 // release cond2 after select has gotten to run
  78                 release = func() {
  79                         cond2.Broadcast()
  80                         time.Sleep(1 * time.Millisecond)
  81                 }
  82         }
  83
  84         runtime.GC()
  85
  86         runtime.ReadMemStats(&stats2)
  87
  88         if int(stats2.HeapObjects)-int(stats1.HeapObjects) > 20 { // normally at most 1 or 2; was 300 with leak
  89                 print("BUG: object leak: ", stats.HeapObjects, " -> ", stats1.HeapObjects, " -> ", stats2.HeapObjects, "\n")
  90         }
  91 }