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vault: fix deadlock in SetConfig #6082

Merged
merged 2 commits into from
Aug 6, 2019
Merged

vault: fix deadlock in SetConfig #6082

merged 2 commits into from
Aug 6, 2019

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schmichael
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This seems to be the minimum viable patch for fixing a deadlock between
establishConnection and SetConfig.

SetConfig calls tomb.Kill+tomb.Wait while holding v.lock.
establishConnection needs to acquire v.lock to exit but SetConfig is
holding v.lock until tomb.Wait exits. tomb.Wait can't exit until
establishConnect does!

  SetConfig -> tomb.Wait
     ^              |
     |              v
  v.lock <- establishConnection

This seems to be the minimum viable patch for fixing a deadlock between
establishConnection and SetConfig.

SetConfig calls tomb.Kill+tomb.Wait while holding v.lock.
establishConnection needs to acquire v.lock to exit but SetConfig is
holding v.lock until tomb.Wait exits. tomb.Wait can't exit until
establishConnect does!

```
  SetConfig -> tomb.Wait
     ^              |
     |              v
  v.lock <- establishConnection
```
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@endocrimes endocrimes left a comment

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😭

This is a defensive measure as SetConfig should only be called serially.
@schmichael schmichael merged commit 7d452bf into master Aug 6, 2019
@schmichael schmichael deleted the b-vault-deadlock branch August 6, 2019 22:30
schmichael added a commit that referenced this pull request Aug 6, 2019
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2 participants