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// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build linux && cgo
// On systems that use glibc, calling malloc can create a new arena,
// and creating a new arena can read /sys/devices/system/cpu/online.
// If we are using cgo, we will call malloc when creating a new thread.
// That can break TestExtraFiles if we create a new thread that creates
// a new arena and opens the /sys file while we are checking for open
// file descriptors. Work around the problem by creating threads up front.
// See issue 25628.
package exec_test
import (
"os"
"sync"
"syscall"
"time"
)
func init() {
if os.Getenv("GO_EXEC_TEST_PID") == "" {
return
}
// Start some threads. 10 is arbitrary but intended to be enough
// to ensure that the code won't have to create any threads itself.
// In particular this should be more than the number of threads
// the garbage collector might create.
const threads = 10
var wg sync.WaitGroup
wg.Add(threads)
ts := syscall.NsecToTimespec((100 * time.Microsecond).Nanoseconds())
for i := 0; i < threads; i++ {
go func() {
defer wg.Done()
syscall.Nanosleep(&ts, nil)
}()
}
wg.Wait()
}
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