Add scheduler deadlock detection #15735

1. 
   jamesob commented at 9:40 pm on April 3, 2019: member

   Related to #14289 and follows up on #15205. See a relevant IRC chat here: http://www.erisian.com.au/bitcoin-core-dev/log-2019-01-22.html

   This helps detect deadlocks in the scheduler (and by association validation interface callbacks) by adding a flag which causes the scheduler to execute tasks synchronously in the calling thread. It adds a Travis job that runs the functional test suite with this flag enabled.

   You can verify that the flag works as intended by applying this diff

    0diff --git a/src/test/validation_block_tests.cpp b/src/test/validation_block_tests.cpp
    1index 44432cd0a1..bb4046f119 100644
    2--- a/src/test/validation_block_tests.cpp
    3+++ b/src/test/validation_block_tests.cpp
    4@@ -27,6 +27,7 @@ struct TestSubscriber : public CValidationInterface {
    5 
    6     void UpdatedBlockTip(const CBlockIndex* pindexNew, const CBlockIndex* pindexFork, bool fInitialDownload) override
    7     {
    8+        SyncWithValidationInterfaceQueue();
    9         BOOST_CHECK_EQUAL(m_expected_tip, pindexNew->GetBlockHash());
   10     }
   

   rebuilding with ./configure ... CPPFLAGS="... -DDEBUG_SERIALIZE_SCHEDULER", then running ./src/test/test_bitcoin -t validation_block_tests, and watching as the deadlock detector hulks out.

2. Add -DDEBUG_SERIALIZE_SCHEDULER

   For use in test environments to detect deadlocks in
   CScheduler-managed tasks.

   6470af9d53
3. Add a Travis job that checks for CScheduler deadlocks 64c06a489e
4. 
   jamesob commented at 6:23 pm on April 4, 2019: member

   This segfaults on functional test run at the moment due to a stack overflow thanks to scheduler.cpp:Repeat(), so I’m gonna think about a workaround.
5. jamesob closed this on Apr 4, 2019

   ---

6. pull[bot] referenced this in commit 2c35fe6238 on Apr 30, 2019
7. DrahtBot locked this on Dec 16, 2021

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