// Unlock unlocks m.
// It is a run-time error if m is not locked on entry to Unlock.
//
// A locked Mutex is not associated with a particular goroutine.
// It is allowed for one goroutine to lock a Mutex and then
// arrange for another goroutine to unlock it.
func (m *Mutex) Unlock() {
if xadd(&m.key, -1) == 0 {
// changed from 1 to 0; no contention
return
}
runtime.Semrelease(&m.sema)
}
func HammerSemaphore(s *uint32, loops int, cdone chan bool) {
for i := 0; i < loops; i++ {
runtime.Semacquire(s)
runtime.Semrelease(s)
}
cdone <- true
}
func BenchmarkSemaUncontended(b *testing.B) {
type PaddedSem struct {
sem uint32
pad [32]uint32
}
const CallsPerSched = 1000
procs := runtime.GOMAXPROCS(-1)
N := int32(b.N / CallsPerSched)
c := make(chan bool, procs)
for p := 0; p < procs; p++ {
go func() {
sem := new(PaddedSem)
for atomic.AddInt32(&N, -1) >= 0 {
runtime.Gosched()
for g := 0; g < CallsPerSched; g++ {
runtime.Semrelease(&sem.sem)
runtime.Semacquire(&sem.sem)
}
}
c <- true
}()
}
for p := 0; p < procs; p++ {
<-c
}
}
// Signal wakes one goroutine waiting on c, if there is any.
//
// It is allowed but not required for the caller to hold c.L
// during the call.
func (c *Cond) Signal() {
c.m.Lock()
if c.waiters > 0 {
c.waiters--
runtime.Semrelease(c.sema)
}
c.m.Unlock()
}
func benchmarkSema(b *testing.B, block, work bool) {
const CallsPerSched = 1000
const LocalWork = 100
procs := runtime.GOMAXPROCS(-1)
N := int32(b.N / CallsPerSched)
c := make(chan bool, procs)
c2 := make(chan bool, procs/2)
sem := uint32(0)
if block {
for p := 0; p < procs/2; p++ {
go func() {
runtime.Semacquire(&sem)
c2 <- true
}()
}
}
for p := 0; p < procs; p++ {
go func() {
foo := 0
for atomic.AddInt32(&N, -1) >= 0 {
runtime.Gosched()
for g := 0; g < CallsPerSched; g++ {
runtime.Semrelease(&sem)
if work {
for i := 0; i < LocalWork; i++ {
foo *= 2
foo /= 2
}
}
runtime.Semacquire(&sem)
}
}
c <- foo == 42
runtime.Semrelease(&sem)
}()
}
if block {
for p := 0; p < procs/2; p++ {
<-c2
}
}
for p := 0; p < procs; p++ {
<-c
}
}
// Broadcast wakes all goroutines waiting on c.
//
// It is allowed but not required for the caller to hold c.L
// during the call.
func (c *Cond) Broadcast() {
c.m.Lock()
// Wake both generations.
if c.oldWaiters > 0 {
for i := 0; i < c.oldWaiters; i++ {
runtime.Semrelease(c.oldSema)
}
c.oldWaiters = 0
}
if c.newWaiters > 0 {
for i := 0; i < c.newWaiters; i++ {
runtime.Semrelease(c.newSema)
}
c.newWaiters = 0
c.newSema = nil
}
c.m.Unlock()
}
// RUnlock undoes a single RLock call;
// it does not affect other simultaneous readers.
// It is a run-time error if rw is not locked for reading
// on entry to RUnlock.
func (rw *RWMutex) RUnlock() {
if atomic.AddInt32(&rw.readerCount, -1) < 0 {
// A writer is pending.
if atomic.AddInt32(&rw.readerWait, -1) == 0 {
// The last reader unblocks the writer.
runtime.Semrelease(&rw.writerSem)
}
}
}
// Unlock unlocks rw for writing. It is a run-time error if rw is
// not locked for writing on entry to Unlock.
//
// As with Mutexes, a locked RWMutex is not associated with a particular
// goroutine. One goroutine may RLock (Lock) an RWMutex and then
// arrange for another goroutine to RUnlock (Unlock) it.
func (rw *RWMutex) Unlock() {
// Announce to readers there is no active writer.
r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders)
// Unblock blocked readers, if any.
for i := 0; i < int(r); i++ {
runtime.Semrelease(&rw.readerSem)
}
// Allow other writers to proceed.
rw.w.Unlock()
}
// Unlock unlocks m.
// It is a run-time error if m is not locked on entry to Unlock.
//
// A locked Mutex is not associated with a particular goroutine.
// It is allowed for one goroutine to lock a Mutex and then
// arrange for another goroutine to unlock it.
func (m *Mutex) Unlock() {
switch v := atomic.AddInt32(&m.key, -1); {
case v == 0:
// changed from 1 to 0; no contention
return
case v == -1:
// changed from 0 to -1: wasn't locked
// (or there are 4 billion goroutines waiting)
panic("sync: unlock of unlocked mutex")
}
runtime.Semrelease(&m.sema)
}
// Signal wakes one goroutine waiting on c, if there is any.
//
// It is allowed but not required for the caller to hold c.L
// during the call.
func (c *Cond) Signal() {
c.m.Lock()
if c.oldWaiters == 0 && c.newWaiters > 0 {
// Retire old generation; rename new to old.
c.oldWaiters = c.newWaiters
c.oldSema = c.newSema
c.newWaiters = 0
c.newSema = nil
}
if c.oldWaiters > 0 {
c.oldWaiters--
runtime.Semrelease(c.oldSema)
}
c.m.Unlock()
}
// Add adds delta, which may be negative, to the WaitGroup counter.
// If the counter becomes zero, all goroutines blocked on Wait() are released.
func (wg *WaitGroup) Add(delta int) {
wg.m.Lock()
if delta < -wg.counter {
wg.m.Unlock()
panic("sync: negative WaitGroup count")
}
wg.counter += delta
if wg.counter == 0 && wg.waiters > 0 {
for i := 0; i < wg.waiters; i++ {
runtime.Semrelease(wg.sema)
}
wg.waiters = 0
wg.sema = nil
}
wg.m.Unlock()
}
// Add adds delta, which may be negative, to the WaitGroup counter.
// If the counter becomes zero, all goroutines blocked on Wait() are released.
func (wg *WaitGroup) Add(delta int) {
v := atomic.AddInt32(&wg.counter, int32(delta))
if v < 0 {
panic("sync: negative WaitGroup count")
}
if v > 0 || atomic.LoadInt32(&wg.waiters) == 0 {
return
}
wg.m.Lock()
for i := int32(0); i < wg.waiters; i++ {
runtime.Semrelease(wg.sema)
}
wg.waiters = 0
wg.sema = nil
wg.m.Unlock()
}
// Broadcast wakes all goroutines waiting on c.
//
// It is allowed but not required for the caller to hold c.L
// during the call.
func (c *Cond) Broadcast() {
c.m.Lock()
if c.waiters > 0 {
s := c.sema
n := c.waiters
for i := 0; i < n; i++ {
runtime.Semrelease(s)
}
// We just issued n wakeups via the semaphore s.
// To ensure that they wake up the existing waiters
// and not waiters that arrive after Broadcast returns,
// clear c.sema. The next operation will allocate
// a new one.
c.sema = nil
c.waiters = 0
}
c.m.Unlock()
}
// Unlock unlocks m.
// It is a run-time error if m is not locked on entry to Unlock.
//
// A locked Mutex is not associated with a particular goroutine.
// It is allowed for one goroutine to lock a Mutex and then
// arrange for another goroutine to unlock it.
func (m *Mutex) Unlock() {
// Fast path: drop lock bit.
new := atomic.AddInt32(&m.state, -mutexLocked)
if (new+mutexLocked)&mutexLocked == 0 {
panic("sync: unlock of unlocked mutex")
}
old := new
for {
// If there are no waiters or a goroutine has already
// been woken or grabbed the lock, no need to wake anyone.
if old>>mutexWaiterShift == 0 || old&(mutexLocked|mutexWoken) != 0 {
return
}
// Grab the right to wake someone.
new = (old - 1<<mutexWaiterShift) | mutexWoken
if atomic.CompareAndSwapInt32(&m.state, old, new) {
runtime.Semrelease(&m.sema)
return
}
old = m.state
}
}
func (this *Semaphore) V() { runtime.Semrelease((*uint32)(this)) }
func (p *Parker) Unpark() {
runtime.Semrelease(&p.sema)
}