fuzz: Use ImmediateBackgroundTaskRunner in process_messages #36046

1. 
   maflcko commented at 6:26 PM on August 20, 2026: member

   The process_messages target may complain about false-positive debug lock-order issues:

   echo 'Gv8uXPBdXV0QEP//dHVhxyoVKP////8A/0BrLmNrAEEAIP+MXHR0OQAAAAD+///txgIUADBgAAEC
   fgAAAK0ArQEAAAD/AFwAQf9cdHf5XGhlYWRlcltbyzHIw8RcX2Jsb2NrAAAAAGNtcAAAADAftOvd
   D0sFqXEx6US5VIknlsOJqZ5goMwtmwZBPdCxQZbatBsWPOR3FcUvSLLsKwcgKT8XdmjvDgskH5pK
   iAUI/uVJTf//fyAAAAAAAQIAAAAAAQEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAP//
   //8DAskA/v///wIA+QKVAAAAAAFRAAAAAAAAAAAmaiSqIant4vYcP3HR3v0/qZnfo2lTdVxcaQaJ
   eZlitIvr2DaXToz5ASAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMgAAAD/XPB0eAD/
   AgAAAAD9ABZqCwAAAAAEAAAAXPBhYVtbW1tbW1tbW1tbW1tbW1tbW1tbW1tbW1tbW1tbW1tbW1tb
   W1tb//9bW1tbW1tbW1sAAAAxNgAAADc5MzU5NDk2ODEwNzg3NAAAAAICAgL9a4jAhyQCAgICAQAA
   AAAABSpvdGhlcir/8wICAgICAAAAeAL0AAAAAAAAaW52O///BAAAAAAAtbW1tWFbW2FhtbVhYWFh
   YSkpW1tbW2QAJwAAAAAAAAAAMTYAAAA3OTM1OTQ5NjgxMDc4NzQAAAACAgIC/WuIwIckAgICAgEA
   AAAAAAUAAAAAAv7///MAeAL0AAAAAAAAaW52Ow==' | base64 --decode > /tmp/fuzz.input
   
   FUZZ=process_messages ./bld-cmake/bin/fuzz /tmp/fuzz.input --printtoconsole=1 | grep -A99 'POTENTIAL DEADLOCK DETECTED'
   

   [test] [sync.cpp:108] [potential_deadlock_detected] [error] POTENTIAL DEADLOCK DETECTED
   [test] [sync.cpp:109] [potential_deadlock_detected] [error] Previous lock order was:
   [test] [sync.cpp:118] [potential_deadlock_detected] [error]  'NetEventsInterface::g_msgproc_mutex' in test/fuzz/process_messages.cpp:89 (in thread 'test')
   [test] [sync.cpp:118] [potential_deadlock_detected] [error]  'm_chainstate_mutex' in validation.cpp:3351 (in thread 'test')
   [test] [sync.cpp:118] [potential_deadlock_detected] [error]  'cs_main' in validation.cpp:3373 (in thread 'test') 
   [test] [sync.cpp:118] [potential_deadlock_detected] [error]  (2) 'MempoolMutex()' in validation.cpp:3376 (in thread 'test')
   [test] [sync.cpp:118] [potential_deadlock_detected] [error]  (1) 'm_tx_download_mutex' in net_processing.cpp:2216 (in thread 'test')
   [test] [sync.cpp:122] [potential_deadlock_detected] [error] Current lock order is: 
   [test] [sync.cpp:133] [potential_deadlock_detected] [error]  'NetEventsInterface::g_msgproc_mutex' in test/fuzz/process_messages.cpp:89 (in thread 'test')
   [test] [sync.cpp:133] [potential_deadlock_detected] [error]  'cs_main' in net_processing.cpp:4725 (in thread 'test')
   [test] [sync.cpp:133] [potential_deadlock_detected] [error]  (1) 'm_tx_download_mutex' in net_processing.cpp:4725 (in thread 'test')
   [test] [sync.cpp:133] [potential_deadlock_detected] [error]  (2) 'cs' in txmempool.h:521 (in thread 'test')
   

   Fix this by using the ImmediateBackgroundTaskRunner from src/test/fuzz/cmpctblock.cpp.

2. fuzz: Use ImmediateBackgroundTaskRunner in process_messages fae6665f01
3. DrahtBot added the label Fuzzing on Aug 20, 2026
4. 
   DrahtBot commented at 6:26 PM on August 20, 2026: contributor

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   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/36046.

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5. maflcko added this to the milestone 32.0 on Aug 20, 2026
6. 
   frankomosh commented at 6:39 PM on August 20, 2026: contributor

   Concept ACK

Milestone
32.0