</p>

<pre>
// A Mutex is a data type with two methods, Lock and Unlock.
type Mutex struct         { /* Mutex fields */ }
func (m *Mutex) Lock()    { /* Lock implementation */ }
func (m *Mutex) Unlock()  { /* Unlock implementation */ }

// NewMutex has the same composition as Mutex but its method set is empty.
type NewMutex Mutex

pkg syscall (darwin-386), const IP_MAXPACKET = 65535
pkg syscall (darwin-386), const IP_MAX_GROUP_SRC_FILTER = 512
pkg syscall (darwin-386), const IP_MAX_MEMBERSHIPS = 4095
pkg syscall (darwin-386), const IP_MAX_SOCK_MUTE_FILTER = 128
pkg syscall (darwin-386), const IP_MAX_SOCK_SRC_FILTER = 128
pkg syscall (darwin-386), const IP_MF = 8192
pkg syscall (darwin-386), const IP_MIN_MEMBERSHIPS = 31

var urlq = make(chan string) // URLs to crawl

// urlFrag is a URL and its optional #fragment (without the #)
type urlFrag struct {
	url, frag string
}

var (
	mu          sync.Mutex
	crawled     = make(map[string]bool)      // URL without fragment -> true
	neededFrags = make(map[urlFrag][]string) // URL#frag -> who needs it
)

var aRx = regexp.MustCompile(`<a href=['"]?(/[^\s'">]+)`)

[GC guide](/doc/gc-guide#Linux_transparent_huge_pages), or switch to a Linux
distribution that disables transparent huge pages altogether.

Go 1.22 added contention on runtime-internal locks to the [`mutex`
profile](/pkg/runtime/pprof#Profile). Contention on these locks is always
reported at `runtime._LostContendedRuntimeLock`. Complete stack traces of
runtime locks can be enabled with the [`runtimecontentionstacks`

pkg syscall (freebsd-riscv64), const IP_MAX_MEMBERSHIPS = 4095 #53466
pkg syscall (freebsd-riscv64), const IP_MAX_MEMBERSHIPS ideal-int #53466
pkg syscall (freebsd-riscv64), const IP_MAX_SOCK_MUTE_FILTER = 128 #53466
pkg syscall (freebsd-riscv64), const IP_MAX_SOCK_MUTE_FILTER ideal-int #53466
pkg syscall (freebsd-riscv64), const IP_MAX_SOCK_SRC_FILTER = 128 #53466
pkg syscall (freebsd-riscv64), const IP_MAX_SOCK_SRC_FILTER ideal-int #53466

</p>

<pre>
// A Mutex is a data type with two methods, Lock and Unlock.
type Mutex struct         { /* Mutex fields */ }
func (m *Mutex) Lock()    { /* Lock implementation */ }
func (m *Mutex) Unlock()  { /* Unlock implementation */ }

// NewMutex has the same composition as Mutex but its method set is empty.
type NewMutex Mutex

*/
import "C"

import (
	"path"
	"runtime"
	"strings"
	"sync"
	"testing"
	"unsafe"
)

// Pass a func value from nestedCall to goCallback using an integer token.
var callbackMutex sync.Mutex
var callbackToken int
var callbackFuncs = make(map[int]func())

// nestedCall calls into C, back into Go, and finally to f.
func nestedCall(f func()) {
	// callback(x) calls goCallback(x)
	callbackMutex.Lock()

//   t = calloc(nts, sizeof(pthread_t));
//   pthread_mutex_init(&mu, NULL);
//   for (i = 0; i < nts; i++) {
//     pthread_create(&t[i], NULL, aFn, NULL);
//   }
// }
//
// void cleanup(void) {
//   int i;
//   pthread_mutex_lock(&mu);
//   all_done = 1;
//   pthread_mutex_unlock(&mu);
//   for (i = 0; i < nts; i++) {
//     pthread_join(t[i], NULL);
//   }
//   pthread_mutex_destroy(&mu);
//   free(t);
// }
import "C"

	fw, ok := flateWriterPool.Get().(*flate.Writer)
	if ok {
		fw.Reset(w)
	} else {
		fw, _ = flate.NewWriter(w, 5)
	}
	return &pooledFlateWriter{fw: fw}
}

type pooledFlateWriter struct {
	mu sync.Mutex // guards Close and Write
	fw *flate.Writer
}

func (w *pooledFlateWriter) Write(p []byte) (n int, err error) {
	w.mu.Lock()
	defer w.mu.Unlock()
	if w.fw == nil {
		return 0, errors.New("Write after Close")
	}

pkg runtime/debug, type BuildSetting struct, Value string
pkg strings, func Clone(string) string
pkg strings, func Cut(string, string) (string, string, bool)
pkg strings, func Title //deprecated
pkg sync, method (*Mutex) TryLock() bool
pkg sync, method (*RWMutex) TryLock() bool
pkg sync, method (*RWMutex) TryRLock() bool
pkg syscall (freebsd-386), type SysProcAttr struct, Pdeathsig Signal