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executor: synchronize exitState accesses #5433

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merged 1 commit into from
Mar 18, 2019
Merged

executor: synchronize exitState accesses #5433

merged 1 commit into from
Mar 18, 2019

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notnoop
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@notnoop notnoop commented Mar 18, 2019

exitState is set in wait() goroutine but accessed in a different
Wait() goroutine, so accesses must be synchronized by a lock.

executor: synchronize exitState accesses
989175f 
exitState is set in `wait()` goroutine but accessed in a different
`Wait()` goroutine, so accesses must be synchronized by a lock.
@notnoop notnoop requested a review from schmichael March 18, 2019 15:15
nickethier
nickethier approved these changes Mar 18, 2019
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lgtm

@notnoop notnoop merged commit b3bedeb into master Mar 18, 2019
@notnoop notnoop deleted the b-exit-state-lock branch March 18, 2019 17:50
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Did the race detector complain? I don't see the race because exitState is set before processExited is closed, and read after processExited is received. I think processExited properly serializes access.

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notnoop commented Mar 18, 2019

tbh, I didn't check the race detector :(, just assumed by reading code; didn't realize that channel operations constitutes happens-before relationship for other variables. But you are right: https://golang.org/ref/mem#tmp_7 - thanks. I can revert this to simplify code.

@notnoop notnoop mentioned this pull request Mar 20, 2019
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@notnoop
Revert "executor: synchronize exitState accesses" (#5449)
a0d025e 
Reverts #5433

Apparently, channel communications can constitute Happens-Before even for proximate variables, so this syncing isn't necessary.

> _The closing of a channel happens before a receive that returns a zero value because the channel is closed._
https://golang.org/ref/mem#tmp_7
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@nickethier nickethier nickethier approved these changes

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