// Lock 用于锁定 m。
// 若该锁正在使用，调用的Go程就会阻塞，直到该互斥体可用。
func (m *Mutex) Lock() {
// Fast path: grab unlocked mutex.
// 快速通道：抢占锁定的互斥体。
if atomic.CompareAndSwapInt32(&m.state, 0, mutexLocked) {
if race.Enabled {
race.Acquire(unsafe.Pointer(m))
}
return
}
awoke := false
iter := 0
for {
old := m.state
new := old | mutexLocked
if old&mutexLocked != 0 {
if runtime_canSpin(iter) {
// Active spinning makes sense.
// Try to set mutexWoken flag to inform Unlock
// to not wake other blocked goroutines.
if !awoke && old&mutexWoken == 0 && old>>mutexWaiterShift != 0 &&
atomic.CompareAndSwapInt32(&m.state, old, old|mutexWoken) {
awoke = true
}
runtime_doSpin()
iter++
continue
}
new = old + 1<<mutexWaiterShift
}
if awoke {
// The goroutine has been woken from sleep,
// so we need to reset the flag in either case.
// 此Go程已从睡眠状态被唤醒，因此无论在哪种状态下，
// 我们都需要充值此标记。
if new&mutexWoken == 0 {
panic("sync: inconsistent mutex state")
}
new &^= mutexWoken
}
if atomic.CompareAndSwapInt32(&m.state, old, new) {
if old&mutexLocked == 0 {
break
}
runtime_Semacquire(&m.sema)
awoke = true
iter = 0
}
}
if race.Enabled {
race.Acquire(unsafe.Pointer(m))
}
}
// Get selects an arbitrary item from the Pool, removes it from the
// Pool, and returns it to the caller.
// Get may choose to ignore the pool and treat it as empty.
// Callers should not assume any relation between values passed to Put and
// the values returned by Get.
//
// If Get would otherwise return nil and p.New is non-nil, Get returns
// the result of calling p.New.
func (p *Pool) Get() interface{} {
if race.Enabled {
race.Disable()
}
l := p.pin()
x := l.private
l.private = nil
runtime_procUnpin()
if x == nil {
l.Lock()
last := len(l.shared) - 1
if last >= 0 {
x = l.shared[last]
l.shared = l.shared[:last]
}
l.Unlock()
if x == nil {
x = p.getSlow()
}
}
if race.Enabled {
race.Enable()
if x != nil {
race.Acquire(poolRaceAddr(x))
}
}
if x == nil && p.New != nil {
x = p.New()
}
return x
}
// Lock locks rw for writing.
// If the lock is already locked for reading or writing,
// Lock blocks until the lock is available.
// To ensure that the lock eventually becomes available,
// a blocked Lock call excludes new readers from acquiring
// the lock.
func (rw *RWMutex) Lock() {
if race.Enabled {
_ = rw.w.state
race.Disable()
}
// First, resolve competition with other writers.
rw.w.Lock()
// Announce to readers there is a pending writer.
r := atomic.AddInt32(&rw.readerCount, -rwmutexMaxReaders) + rwmutexMaxReaders
// Wait for active readers.
if r != 0 && atomic.AddInt32(&rw.readerWait, r) != 0 {
runtime_Semacquire(&rw.writerSem)
}
if race.Enabled {
race.Enable()
race.Acquire(unsafe.Pointer(&rw.readerSem))
race.Acquire(unsafe.Pointer(&rw.writerSem))
}
}
// Wait 阻塞 WaitGroup 直到其 counter 为零。
func (wg *WaitGroup) Wait() {
statep := wg.state()
if race.Enabled {
_ = *statep // trigger nil deref early
race.Disable()
}
for {
state := atomic.LoadUint64(statep)
v := int32(state >> 32)
w := uint32(state)
if v == 0 {
// Counter is 0, no need to wait.
// 计数器为 0，无需等待。
if race.Enabled {
race.Enable()
race.Acquire(unsafe.Pointer(wg))
}
return
}
// Increment waiters count.
// 递增等待者计数。
if atomic.CompareAndSwapUint64(statep, state, state+1) {
if race.Enabled && w == 0 {
// Wait must be synchronized with the first Add.
// Need to model this is as a write to race with the read in Add.
// As a consequence, can do the write only for the first waiter,
// otherwise concurrent Waits will race with each other.
race.Write(unsafe.Pointer(&wg.sema))
}
runtime_Semacquire(&wg.sema)
if *statep != 0 {
panic("sync: WaitGroup is reused before previous Wait has returned")
}
if race.Enabled {
race.Enable()
race.Acquire(unsafe.Pointer(wg))
}
return
}
}
}
// RLock locks rw for reading.
func (rw *RWMutex) RLock() {
if race.Enabled {
_ = rw.w.state
race.Disable()
}
if atomic.AddInt32(&rw.readerCount, 1) < 0 {
// A writer is pending, wait for it.
runtime_Semacquire(&rw.readerSem)
}
if race.Enabled {
race.Enable()
race.Acquire(unsafe.Pointer(&rw.readerSem))
}
}
func Read(fd int, p []byte) (n int, err error) {
n, err = read(fd, p)
if race.Enabled {
if n > 0 {
race.WriteRange(unsafe.Pointer(&p[0]), n)
}
if err == nil {
race.Acquire(unsafe.Pointer(&ioSync))
}
}
if msanenabled && n > 0 {
msanWrite(unsafe.Pointer(&p[0]), n)
}
return
}
func (fd *netFD) Read(buf []byte) (int, error) {
if err := fd.readLock(); err != nil {
return 0, err
}
defer fd.readUnlock()
o := &fd.rop
o.InitBuf(buf)
n, err := rsrv.ExecIO(o, "WSARecv", func(o *operation) error {
return syscall.WSARecv(o.fd.sysfd, &o.buf, 1, &o.qty, &o.flags, &o.o, nil)
})
if race.Enabled {
race.Acquire(unsafe.Pointer(&ioSync))
}
err = fd.eofError(n, err)
if _, ok := err.(syscall.Errno); ok {
err = os.NewSyscallError("wsarecv", err)
}
return n, err
}
func Read(fd Handle, p []byte) (n int, err error) {
var done uint32
e := ReadFile(fd, p, &done, nil)
if e != nil {
if e == ERROR_BROKEN_PIPE {
// NOTE(brainman): work around ERROR_BROKEN_PIPE is returned on reading EOF from stdin
return 0, nil
}
return 0, e
}
if race.Enabled {
if done > 0 {
race.WriteRange(unsafe.Pointer(&p[0]), int(done))
}
race.Acquire(unsafe.Pointer(&ioSync))
}
if msanenabled && done > 0 {
msanWrite(unsafe.Pointer(&p[0]), int(done))
}
return int(done), nil
}