fix race conditions in conn.go #134
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- closeCount renamed to closing; acts as atomic bool
- once replaced with atomic.CompareAndSwapUint32 in setClosing method
- wgSender removed:
- Close could call wgSender.Wait while another goroutine is about to
call wgSender.Add; this is detected by the race detector as a race
condition if Wait hasn't yet returned. the WaitGroup documentation
also lists this scenario as an error.
- the intent appears to be to let all messages queue in the buffered
chan 'chanMessage' before sending MessageQuit. the WaitGroup could
reach 0 and be incremented again by a goroutine which successfully
passed isClosing, therefore the WaitGroup isn't a strong enough
guarantee. this is addressed in the next commit.
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Nit on defer unlock. Lgtm otherwise, thanks |
- in order to guarantee the Op: MessageQuit is the last in chanMessage we need to lock messageMutex (or any mutex) before setting 'closing' in the Close method and before checking it in the sendProcessMessage method. - there may be other ways to do this, such as sending the close message to a different channel and then draining the chanMessage channel. this would require more accounting work
- remove l.chanMessageID != nil check; setting the chan to nil was removed in 3bda2b4 - change chanConfirm to chan struct{}; remove send, just close - log.Print -> log.Println - since the intention is to close chanMessage after calling Close and receiving on chanConfirm (in the defer of processMessages) the channel should not be closed in the for/select loop
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@liggitt Done. |
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Nov 23, 2017
fix race conditions in conn.go
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I just came across this package tonight, so I'm unfamiliar with its use in real scenarios. I may also be unfamiliar with nuances in the code. If someone could try this in their setup or recommend which use cases need tests I'll happily add them.
/cc @johnweldon @liggitt