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  }
    46
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