issue11256.go

     1  // run
     2  
     3  // Copyright 2015 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  // Test that stack barriers are reset when a goroutine exits without
     8  // returning.
     9  
    10  package main
    11  
    12  import (
    13  	"runtime"
    14  	"sync/atomic"
    15  	"time"
    16  )
    17  
    18  func main() {
    19  	// Let the garbage collector run concurrently.
    20  	runtime.GOMAXPROCS(2)
    21  
    22  	var x [100][]byte
    23  
    24  	for i := range x {
    25  		var done int32
    26  
    27  		go func() {
    28  			// Use enough stack to get stack barriers, but
    29  			// not so much that we go over _FixedStack.
    30  			// There's a very narrow window here on most
    31  			// OSs, so we basically can't do anything (not
    32  			// even a time.Sleep or a channel).
    33  			var buf [1024]byte
    34  			buf[0]++
    35  			for atomic.LoadInt32(&done) == 0 {
    36  				runtime.Gosched()
    37  			}
    38  			atomic.StoreInt32(&done, 0)
    39  			// Exit without unwinding stack barriers.
    40  			runtime.Goexit()
    41  		}()
    42  
    43  		// Generate some garbage.
    44  		x[i] = make([]byte, 1024*1024)
    45  
    46  		// Give GC some time to install stack barriers in the G.
    47  		time.Sleep(50 * time.Microsecond)
    48  		atomic.StoreInt32(&done, 1)
    49  		for atomic.LoadInt32(&done) == 1 {
    50  			runtime.Gosched()
    51  		}
    52  	}
    53  }
    54
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