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Created attachment 9560 [details]
Compile & run attached test case.
* Execution hangs.
* Execution completes (this is the expected behavior, this usually happens when the app exits before the background threads has started).
* Random crashes.
Created attachment 9561 [details]
Assortion of logs (zipped)
All the threads seem to be stuck here:
#0 0x00007fff8c236716 in __psynch_cvwait ()
#1 0x00007fff8eaf5c3b in _pthread_cond_wait ()
#2 0x000000010f8b62f6 in _wapi_handle_timedwait_signal_handle (handle=0x16a, timeout=0x0, alertable=1, poll=0) at handles.c:1617
#3 0x000000010f8b638d in _wapi_handle_wait_signal_handle (handle=0x16a, alertable=1) at handles.c:1562
#4 0x000000010f8d08e3 in wapi_WaitForSingleObjectEx (handle=0x16a, timeout=4294967295, alertable=1) at wait.c:194
#5 0x000000010f813e9b in mono_monitor_try_enter_internal (obj=0x110c05700, ms=4294967295, allow_interruption=1) at monitor.c:665
#6 0x000000010f814434 in ves_icall_System_Threading_Monitor_Monitor_try_enter_with_atomic_var (obj=0x110c05700, ms=4294967295, lockTaken=0x1244e38b0 "") at monitor.c:866
#7 0x000000010f8144cf in mono_monitor_enter_v4 (obj=0x110c05700, lock_taken=0x1244e38b0 "") at monitor.c:881
#8 0x000000010f60ec21 in mono_monitor_enter_v4_trampoline (regs=0x1244e37e8, code=0x110bbb293 "I?E(H??H?u?H?U?H?", obj=0x110c05700, tramp=0x110b775d5 "?F\024??\004") at mini-trampolines.c:970
I cannot reproduce with Mono 18.104.22.168 (master/798c5efa52a). I ran it in a loop ~200 times and it didn't hang nor crash.