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_EXEC_TEST_PID") == "" { 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 } 46