They are the lock count for the given lock. Imagine each lock keeps track
of how many times it has been acquired.
There is a happens-before edge from an unlock to a lock only if the unlock
has a lower count (i.e. was earlier than) than the lock.
On Mon, Oct 23, 2017 at 3:43 PM, T L <tapir....@gmail.com> wrote:
> Thanks all for the explanations.
>
> I still have one question, which has been mentioned above.
>
> > For any sync.Mutex or sync.RWMutex variable l and *n* < *m*, call *n*
> of l.Unlock() happens before call *m* of l.Lock() returns.
>
> What are the "n" and "m" here?
>
> On Saturday, October 21, 2017 at 5:01:08 PM UTC-4, T L wrote:
>>
>> package main
>>
>> import "fmt"
>> import "sync"
>> import "sync/atomic"
>>
>> func main() {
>> var a, b int32 = 0, 0
>>
>> go func() {
>> a = 1
>> atomic.AddInt32(&b, 1)
>> }()
>>
>> for {
>> if n := atomic.LoadInt32(&b); n == 1 {
>> fmt.Println(a) // always print 1?
>> break
>> }
>> }
>>
>> //======================
>>
>> var x, y int32 = 0, 0
>> var m sync.Mutex
>>
>> go func() {
>> x = 1
>> m.Lock()
>> y++
>> m.Unlock()
>> }()
>>
>> for {
>> m.Lock()
>> n := y
>> m.Unlock()
>> if n == 1 {
>> fmt.Println(x) // always print 1?
>> break
>> }
>> }
>> }
>>
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