fix(qt): Fix overlapping directory lock attempts when restarting Dash Qt #6540

kwvg · 2025-01-27T03:21:36Z

Expected Behavior

Start Dash Qt
Go to Window > Wallet Repair and click on "Rebuild Index"
Dash Qt restarts and starts reindexing chain
🎉

Actual Behavior

Start Dash Qt
Go to Window > Wallet Repair and click on "Rebuild Index"
Dash Qt exits and on the restart, get greeted by "Error: Cannot obtain a lock on data directory /home/dash/.dashcore. Dash Core is probably already running."
Run the client again
Reindexing starts

Additional Information

Running the client after reindexing is requested (i.e. on restart) was found to result in a nullptr-induced crash (see below) even though DeploymentActiveAfter() handles a nullptr case (source). This has been resolved by returning early if pindex is a nullptr. Addressed by dash#6537, fix dropped from this PR.

Crash trace:

Posix Signal: Segmentation fault
  0#: (0x557D376F7454) stacktraces.cpp          - HandlePosixSignal(int)
  1#: (0x7F1F6B65B050) <unknown-file>           - ???
  2#: (0x557D36FA2C4F) deploymentstatus.h:20    - DeploymentActiveAfter(CBlockIndex const*, Consensus::Params const&, Consensus::BuriedDeployment)
  3#: (0x557D36FA2C4F) deterministicmns.cpp:220 - CDeterministicMNList::GetProjectedMNPayees(gsl::not_null<CBlockIndex const* const>, int) const
  4#: (0x557D36F2A271) stl_iterator.h:1028      - __gnu_cxx::__normal_iterator<std::shared_ptr<CDeterministicMN const> const*, std::vector<std::shared_ptr<CDeterministicMN const>, std::allocator<std::shared_ptr<CDeterministicMN const> > > >::__normal_iterator(std::shared_ptr<CDeterministicMN const> const* const&)
  5#: (0x557D36F2A271) stl_vector.h:821         - std::vector<std::shared_ptr<CDeterministicMN const>, std::allocator<std::shared_ptr<CDeterministicMN const> > >::begin() const
  6#: (0x557D36F2A271) stl_vector.h:1008        - std::vector<std::shared_ptr<CDeterministicMN const>, std::allocator<std::shared_ptr<CDeterministicMN const> > >::empty() const
  7#: (0x557D36F2A271) masternodelist.cpp:169   - MasternodeList::updateDIP3List()
  8#: (0x557D36F29D30) masternodelist.cpp:147   - MasternodeList::updateDIP3ListScheduled()
  9#: (0x557D37FEE969) <unknown-file>           - ???
 10#: (0x557D37FF4AA2) <unknown-file>           - ???
 11#: (0x557D37FE7843) <unknown-file>           - ???
 12#: (0x557D3821AC0C) <unknown-file>           - ???
 13#: (0x557D3821BEDE) <unknown-file>           - ???
 14#: (0x557D37FCA888) <unknown-file>           - ???
 15#: (0x557D3800C223) <unknown-file>           - ???
 16#: (0x557D3800A02D) <unknown-file>           - ???
 17#: (0x557D3813FD4E) <unknown-file>           - ???
 18#: (0x557D36F57849) sendcoinsdialog.cpp:607  - SendCoinsDialog::addEntry()

Breaking Changes

None expected

Checklist

I have performed a self-review of my own code
I have commented my code, particularly in hard-to-understand areas
I have added or updated relevant unit/integration/functional/e2e tests (note: N/A)
I have made corresponding changes to the documentation (note: N/A)
I have assigned this pull request to a milestone (for repository code-owners and collaborators only)

coderabbitai · 2025-01-27T05:50:27Z

Walkthrough

The pull request introduces a new conditional block at the end of the PrepareShutdown function in src/init.cpp. This block checks if a restart is requested by calling RestartRequested(). If true, it invokes the ReleaseDirectoryLocks() function. This addition ensures that directory locks are explicitly released during the shutdown process when a restart is anticipated, rather than relying on the global context to handle this automatically. The overall structure and logic of the shutdown process remain unchanged, with no lines removed or modified. No changes were made to the declarations of exported or public entities in this diff.

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src/init.cpp (1 hunks)

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src/init.cpp

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GitHub Check: Build Dependencies (linux64, x86_64-pc-linux-gnu)
GitHub Check: Build Dependencies (arm-linux, arm-linux-gnueabihf)

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knst · 2025-01-27T06:38:56Z

src/init.cpp

@@ -359,6 +359,10 @@ void PrepareShutdown(NodeContext& node)

    UnregisterAllValidationInterfaces();
    GetMainSignals().UnregisterBackgroundSignalScheduler();
+


/** Release all directory locks. This is used for unit testing only, at runtime * the global destructor will take care of the locks. */

bitcoin says this one. Why should we do it manually?

Because we implement functionality (restarting, source) that Bitcoin doesn't. The problem occurs because of the following order:

Client started, global context initialized

Managed context initializes

Directory is locked

Client fully loaded, user requests a reindex

Managed context is destroyed

New client instance is started with amended runtime arguments for reindex

Old client instance finishes, global context is destroyed

Directory is unlocked

The problem is that we start the new client (source) before the client gets to fully shutter down (source), which means the directory is still locked when the new instance is trying to run, which results in deviation from expected behavior. This is resolved by releasing the directory locks explicitly, to allow for the new instance to take over.

Could probably wrap it in if (RestartRequested()) { ... } to avoid executing it on shutdown

Wrapped in RestartRequested() and updated comment in latest push

UdjinM6

utACK 59f9c51

kwvg added this to the 22.1 milestone Jan 27, 2025

kwvg force-pushed the fix_restart branch from 62d7a91 to 43be934 Compare January 27, 2025 03:25

kwvg marked this pull request as ready for review January 27, 2025 05:48

kwvg requested review from knst, UdjinM6 and PastaPastaPasta January 27, 2025 05:48

knst reviewed Jan 27, 2025

View reviewed changes

kwvg requested a review from knst January 27, 2025 09:32

fix(qt): Fix overlapping directory lock attempts when restarting Dash Qt

59f9c51

kwvg force-pushed the fix_restart branch from 43be934 to 59f9c51 Compare January 27, 2025 10:49

UdjinM6 approved these changes Jan 27, 2025

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fix(qt): Fix overlapping directory lock attempts when restarting Dash Qt #6540

fix(qt): Fix overlapping directory lock attempts when restarting Dash Qt #6540

kwvg commented Jan 27, 2025 •

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		@@ -359,6 +359,10 @@ void PrepareShutdown(NodeContext& node)

		UnregisterAllValidationInterfaces();
		GetMainSignals().UnregisterBackgroundSignalScheduler();

fix(qt): Fix overlapping directory lock attempts when restarting Dash Qt #6540

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kwvg commented Jan 27, 2025 • edited Loading

Expected Behavior

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Checklist

coderabbitai bot commented Jan 27, 2025 • edited Loading

Walkthrough

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kwvg commented Jan 27, 2025 •

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