libgo/go/os/exec/exec_linux_test.go

   1 // Copyright 2020 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 //go:build linux && cgo
   6
   7 // On systems that use glibc, calling malloc can create a new arena,
   8 // and creating a new arena can read /sys/devices/system/cpu/online.
   9 // If we are using cgo, we will call malloc when creating a new thread.
  10 // That can break TestExtraFiles if we create a new thread that creates
  11 // a new arena and opens the /sys file while we are checking for open
  12 // file descriptors. Work around the problem by creating threads up front.
  13 // See issue 25628.
  14
  15 package exec_test
  16
  17 import (
  18         "os"
  19         "sync"
  20         "syscall"
  21         "time"
  22 )
  23
  24 func init() {
  25         if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" {
  26                 return
  27         }
  28
  29         // Start some threads. 10 is arbitrary but intended to be enough
  30         // to ensure that the code won't have to create any threads itself.
  31         // In particular this should be more than the number of threads
  32         // the garbage collector might create.
  33         const threads = 10
  34
  35         var wg sync.WaitGroup
  36         wg.Add(threads)
  37         ts := syscall.NsecToTimespec((100 * time.Microsecond).Nanoseconds())
  38         for i := 0; i < threads; i++ {
  39                 go func() {
  40                         defer wg.Done()
  41                         syscall.Nanosleep(&ts, nil)
  42                 }()
  43         }
  44         wg.Wait()
  45 }