bindm.go

     1  // Copyright 2023 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 !plan9 && !windows
     6  
     7  // Test that callbacks from C to Go in the same C-thread always get the same m.
     8  // Make sure the extra M bind to the C-thread.
     9  
    10  package main
    11  
    12  /*
    13  extern void CheckBindM();
    14  */
    15  import "C"
    16  
    17  import (
    18  	"fmt"
    19  	"os"
    20  	"runtime"
    21  	"sync"
    22  	"sync/atomic"
    23  )
    24  
    25  var (
    26  	mutex      = sync.Mutex{}
    27  	cThreadToM = map[uintptr]uintptr{}
    28  	started    = atomic.Uint32{}
    29  )
    30  
    31  // same as CTHREADS in C, make sure all the C threads are actually started.
    32  const cThreadNum = 2
    33  
    34  func init() {
    35  	register("EnsureBindM", EnsureBindM)
    36  }
    37  
    38  //export GoCheckBindM
    39  func GoCheckBindM(thread uintptr) {
    40  	// Wait all threads start
    41  	if started.Load() != cThreadNum {
    42  		// Only once for each thread, since it will wait all threads start.
    43  		started.Add(1)
    44  		for started.Load() < cThreadNum {
    45  			runtime.Gosched()
    46  		}
    47  	}
    48  	m := runtime_getm_for_test()
    49  	mutex.Lock()
    50  	defer mutex.Unlock()
    51  	if savedM, ok := cThreadToM[thread]; ok && savedM != m {
    52  		fmt.Printf("m == %x want %x\n", m, savedM)
    53  		os.Exit(1)
    54  	}
    55  	cThreadToM[thread] = m
    56  }
    57  
    58  func EnsureBindM() {
    59  	C.CheckBindM()
    60  	fmt.Println("OK")
    61  }
    62
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