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Fix race condition which permanently pauses sync #5865
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Codecov Report
@@ Coverage Diff @@
## master #5865 +/- ##
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- Coverage 64.05% 63.97% -0.08%
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Files 364 364
Lines 30994 30992 -2
Branches 3435 3435
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- Hits 19852 19826 -26
- Misses 9917 9933 +16
- Partials 1225 1233 +8 |
The problem is that the knownFull -> !knownFull check in BlockQueue::drain() doesn't catch cases where the block queue is modified on a verifier thread - these cases are when a bad block is detected and the block and all of its children are removed from m_verifying, or when a block (with bytes) is moved from m_unverified to m_verifying (without bytes). The fix is to always fire the onRoomAvailable handler (renamed to onBlocksDrained) at the end of doneDrain, and in the handler to only resume syncing if it's paused and the block queue isn't full.
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gumb0
approved these changes
Dec 11, 2019
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@gumb0: Yes kicked it off last night, will let it run for a bit before merging. |
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Ran sync for ~12 hours and sync'd from genesis to block 1.4M without issues. |
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Fix #5312
The race condition occurs when the block queue is full so syncing is paused, and the function which detects when the block queue has room (
BlockQueue::drain) does the first of the two-part check when a block queue verifier thread has temporarily removed block data from the verification queues.As such, the "room available" detection fails and
drainremoves more blocks, which means that the block queue enters a permanently not full state and syncing is paused indefinitely.This is fixed by also performing the "room available" detection check in the body of the block queue verifier threads.