finalizer_deadlock.go

     1  // Copyright 2025 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  package main
     6  
     7  import (
     8  	"flag"
     9  	"fmt"
    10  	"os"
    11  	"runtime"
    12  	"runtime/pprof"
    13  )
    14  
    15  var finalizerDeadlockMode = flag.String("finalizer-deadlock-mode", "panic", "Trigger mode of FinalizerDeadlock")
    16  
    17  func init() {
    18  	register("FinalizerDeadlock", func() { FinalizerOrCleanupDeadlock(false) })
    19  	register("CleanupDeadlock", func() { FinalizerOrCleanupDeadlock(true) })
    20  }
    21  
    22  func FinalizerOrCleanupDeadlock(useCleanup bool) {
    23  	flag.Parse()
    24  
    25  	started := make(chan struct{})
    26  	fn := func() {
    27  		started <- struct{}{}
    28  		select {}
    29  	}
    30  	b := new([16]byte)
    31  	if useCleanup {
    32  		runtime.AddCleanup(b, func(struct{}) { fn() }, struct{}{})
    33  	} else {
    34  		runtime.SetFinalizer(b, func(*[16]byte) { fn() })
    35  	}
    36  	b = nil
    37  
    38  	runtime.GC()
    39  
    40  	<-started
    41  	// We know the finalizer has started running. The goroutine might still
    42  	// be running or it may now be blocked. Either is fine, the goroutine
    43  	// should appear in stacks either way.
    44  
    45  	mode := os.Getenv("GO_TEST_FINALIZER_DEADLOCK")
    46  	switch mode {
    47  	case "panic":
    48  		panic("panic")
    49  	case "stack":
    50  		buf := make([]byte, 4096)
    51  		for {
    52  			n := runtime.Stack(buf, true)
    53  			if n >= len(buf) {
    54  				buf = make([]byte, 2*len(buf))
    55  				continue
    56  			}
    57  			buf = buf[:n]
    58  			break
    59  		}
    60  		fmt.Printf("%s\n", string(buf))
    61  	case "pprof_proto":
    62  		if err := pprof.Lookup("goroutine").WriteTo(os.Stdout, 0); err != nil {
    63  			fmt.Fprintf(os.Stderr, "Error writing profile: %v\n", err)
    64  			os.Exit(1)
    65  		}
    66  	case "pprof_debug1":
    67  		if err := pprof.Lookup("goroutine").WriteTo(os.Stdout, 1); err != nil {
    68  			fmt.Fprintf(os.Stderr, "Error writing profile: %v\n", err)
    69  			os.Exit(1)
    70  		}
    71  	case "pprof_debug2":
    72  		if err := pprof.Lookup("goroutine").WriteTo(os.Stdout, 2); err != nil {
    73  			fmt.Fprintf(os.Stderr, "Error writing profile: %v\n", err)
    74  			os.Exit(1)
    75  		}
    76  	default:
    77  		fmt.Fprintf(os.Stderr, "Unknown mode %q. GO_TEST_FINALIZER_DEADLOCK must be one of panic, stack, pprof_proto, pprof_debug1, pprof_debug2\n", mode)
    78  		os.Exit(1)
    79  	}
    80  }
    81
View as plain text