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affected/package: sync #50544
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Can you please provide a runnable code sample that demonstrates the problem. Thank you. |
func (wg *WaitGroup) Add(delta int) {
statep, semap := wg.state()
if race.Enabled {
_ = *statep // trigger nil deref early
if delta < 0 {
// Synchronize decrements with Wait.
race.ReleaseMerge(unsafe.Pointer(wg))
}
race.Disable()
defer race.Enable()
}
state := atomic.AddUint64(statep, uint64(delta)<<32)
// (1) the first one suspend there, but couter has been change .other one call Add(1) assume positive number
v := int32(state >> 32)
w := uint32(state)
if race.Enabled && delta > 0 && v == int32(delta) {
// The first increment must be synchronized with Wait.
// Need to model this as a read, because there can be
// several concurrent wg.counter transitions from 0.
race.Read(unsafe.Pointer(semap))
}
if v < 0 {
panic("sync: negative WaitGroup counter")
}
// (2) other one will succeed atomic Add ,then painc on this
// w > 0 delta > 0 && v=1 delta=1
if w != 0 && delta > 0 && v == int32(delta) {
panic("sync: WaitGroup misuse: Add called concurrently with Wait")
}
if v > 0 || w == 0 {
return
}
// This goroutine has set counter to 0 when waiters > 0.
// Now there can't be concurrent mutations of state:
// - Adds must not happen concurrently with Wait,
// - Wait does not increment waiters if it sees counter == 0.
// Still do a cheap sanity check to detect WaitGroup misuse.
if *statep != state {
panic("sync: WaitGroup misuse: Add called concurrently with Wait")
}
// Reset waiters count to 0.
*statep = 0
for ; w != 0; w-- {
runtime_Semrelease(semap, false, 0)
}
} but in this case ,Add called concurrently with Add ? |
Thank you, sadly this is not a runnable code sample. If I understand your bug report correctly, then you should be able to write e short program that demonstrates the scenario you are describing |
Duplicate of #50525 Unlike many projects, the Go project does not use GitHub Issues for general discussion or asking questions. GitHub Issues are used for tracking bugs and proposals only. For questions please refer to https://github.com/golang/go/wiki/Questions |
What version of Go are you using (
go version
)?Does this issue reproduce with the latest release?
yes
What operating system and processor architecture are you using (
go env
)?go env
OutputWhat did you do?
What did you expect to see?
When I learned the add function, I see the code of panic as follows:
What did you see instead?
The code comment of panic should be changed as
Additional
I am new to use golang, and not sure if I understand this correctly, so let me know if i am wrong.
thanks a lot!
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