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", FinalizerDeadlock)
    19  }
    20  
    21  func FinalizerDeadlock() {
    22  	flag.Parse()
    23  
    24  	started := make(chan struct{})
    25  	b := new([16]byte)
    26  	runtime.SetFinalizer(b, func(*[16]byte) {
    27  		started <- struct{}{}
    28  		select {}
    29  	})
    30  	b = nil
    31  
    32  	runtime.GC()
    33  
    34  	<-started
    35  	// We know the finalizer has started running. The goroutine might still
    36  	// be running or it may now be blocked. Either is fine, the goroutine
    37  	// should appear in stacks either way.
    38  
    39  	mode := os.Getenv("GO_TEST_FINALIZER_DEADLOCK")
    40  	switch mode {
    41  	case "panic":
    42  		panic("panic")
    43  	case "stack":
    44  		buf := make([]byte, 4096)
    45  		for {
    46  			n := runtime.Stack(buf, true)
    47  			if n >= len(buf) {
    48  				buf = make([]byte, 2*len(buf))
    49  				continue
    50  			}
    51  			buf = buf[:n]
    52  			break
    53  		}
    54  		fmt.Printf("%s\n", string(buf))
    55  	case "pprof_proto":
    56  		if err := pprof.Lookup("goroutine").WriteTo(os.Stdout, 0); err != nil {
    57  			fmt.Fprintf(os.Stderr, "Error writing profile: %v\n", err)
    58  			os.Exit(1)
    59  		}
    60  	case "pprof_debug1":
    61  		if err := pprof.Lookup("goroutine").WriteTo(os.Stdout, 1); err != nil {
    62  			fmt.Fprintf(os.Stderr, "Error writing profile: %v\n", err)
    63  			os.Exit(1)
    64  		}
    65  	case "pprof_debug2":
    66  		if err := pprof.Lookup("goroutine").WriteTo(os.Stdout, 2); err != nil {
    67  			fmt.Fprintf(os.Stderr, "Error writing profile: %v\n", err)
    68  			os.Exit(1)
    69  		}
    70  	default:
    71  		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)
    72  		os.Exit(1)
    73  	}
    74  }
    75
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