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PerfMap Reenable Crashing from AssemblyIterator IterateAssembliesEx #123438
Description
Description
PerfMap allows re-enabling through the DiagnosticServer IPC Command PerfMapEnable.
Doing so early in startup (e.g. userevents tests) has led to crashes such as #122472 and the following
00 0000f12a`161eeae0 0000f12a`15b4f918 libc_so+0xd5154
01 0000f12a`161eeb10 0000f12a`15b503c8 libcoreclr!PROCCreateCrashDump+0x510 [/__w/1/s/src/coreclr/pal/src/thread/process.cpp @ 2573]
02 0000f12a`161eeb90 0000f12a`15b1a8e0 libcoreclr!PROCCreateCrashDumpIfEnabled+0x320 [/__w/1/s/src/coreclr/pal/src/thread/process.cpp @ 2822]
03 0000f12a`161eed00 0000f12a`15b19b5c libcoreclr!invoke_previous_action+0x1ac [/__w/1/s/src/coreclr/pal/src/exception/signal.cpp @ 439]
04 0000f12a`161eed50 0000f12a`1627f7a0 libcoreclr!sigsegv_handler+0x1c8
05 0000f12a`161eeda0 0000f12a`157e6458 linux_vdso_so!_kernel_rt_sigreturn
06 (Inline Function) --------`-------- libcoreclr!AppDomain::AssemblyIterator::Create+0x24 [/__w/1/s/src/coreclr/vm/appdomain.hpp @ 1022]
07 (Inline Function) --------`-------- libcoreclr!AppDomain::IterateAssembliesEx+0x24 [/__w/1/s/src/coreclr/vm/baseassemblyspec.h @ 1032]
08 0000f129`d4a1e460 0000f12a`1552c7cc libcoreclr!PerfMap::Enable+0x1a8 [/__w/1/s/src/coreclr/inc/sstring.h @ 124]
09 (Inline Function) --------`-------- libcoreclr!ds_rt_enable_perfmap+0x18 [/__w/1/s/src/coreclr/vm/eventing/eventpipe/ds-rt-coreclr.h @ 317]
0a (Inline Function) --------`-------- libcoreclr!process_protocol_helper_enable_perfmap+0x80 [/__w/1/s/src/native/eventpipe/ds-portable-rid.c @ 1072]
0b 0000f129`d4a1e640 0000f12a`155315e8 libcoreclr!ds_process_protocol_helper_handle_ipc_message+0x31c [/__w/1/s/src/native/eventpipe/ds-portable-rid.c @ 1245]
0c (Inline Function) --------`-------- libcoreclr!server_loop_tick+0x198 [/__w/1/s/src/native/eventpipe/ds-server.c @ 158]
0d 0000f129`d4a1e7e0 0000f12a`15b52d98 libcoreclr!server_thread+0x270 [/__w/1/s/src/native/eventpipe/ds-protocol.c @ 185]
0e 0000f129`d4a1e860 0000f12a`15ce0944 libcoreclr!CorUnix::CPalThread::ThreadEntry+0x350 [/__w/1/s/src/coreclr/pal/src/thread/thread.cpp @ 1601]
0f 0000f129`d4a1e920 0000f12a`15d46ccc libc_so+0x80944
10 0000f129`d4a1ea40 ffffffff`ffffffff libc_so+0xe6ccc
11 0000f129`d4a1ea40 00000000`00000000 0xffffffff`ffffffff
This crash, after bumping PerfMap::Initialize earlier in start-up, reveals that PerfMap Reenable (sendExisting=true) assumes that the command is only sent once AppDomain's AssemblyIterator is able to IterateAssembliesEx.
This is a seldomly hit scenario rather than a regression. Its only being hit now because userevents tests spin up RecordTrace before starting tracee apps and RecordTrace identifies .NET processes and sends a PerfMap Enable IPC Command as early as possible.
The fix is likely gracefully handling assembly iteration at
runtime/src/coreclr/vm/perfmap.cpp
Lines 124 to 125 in 720a61b
Reproduction Steps
Send Enable PerfMap IPC command early in startup
Expected behavior
No crash
Actual behavior
Crashes
Regression?
No
Known Workarounds
Don't send IPC command early in app startup
Configuration
No response
Other information
No response
Activity
dotnet-policy-service commentedon Jan 21, 2026
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