core: Synchronize wait group access in blockchain #23673
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When using a wg Add is intended to be called before Wait, calling Add and Wait concurrently leads to data races. The blockchain calls wg.Add in many exported methods such as chain insert methods and it seems highly unlikely that they will be called by the same goroutine that calls Stop (where wg.Wait is called), so to avoid data races on shutdown the acesses to Add and Wait need to be synchronized. The solution is to lock over calls to Add and Wait. A golang issue with more details about this problem golang/go#23842
piersy
requested review from
holiman,
karalabe and
rjl493456442
as code owners
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A different fix is to remove the silly waitgroups: #22853 . If you're looking into these things, I'd appreciate if you take a look at that PR, if it seems ok to you. |
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I strongly prefer #22853 over this PR. |
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When using a wg Add is intended to be called before Wait, calling Add
and Wait concurrently leads to data races.
See a simple example of this problem here:
golang/go#23842
The blockchain calls wg.Add in many exported methods such as chain
insert methods and it seems highly unlikely that they will be called by
the same goroutine that calls Stop (where wg.Wait is called), so to
avoid data races on shutdown the acesses to Add and Wait need to be
synchronized.
The solution here is to lock over calls to Add and Wait.