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[release/10.0] Change PerfMap CRST to use UNSAFE_ANYMODE #128430

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[release/10.0] Change PerfMap CRST to use UNSAFE_ANYMODE #128430

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12 changes: 10 additions & 2 deletions src/coreclr/vm/perfmap.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,15 @@ void PerfMap::Initialize()
{
LIMITED_METHOD_CONTRACT;

s_csPerfMap.Init(CrstPerfMap);
// Use CRST_UNSAFE_ANYMODE to avoid a GC-mode toggle deadlock: callers such as
// CodeFragmentHeap::RealAllocAlignedMem hold CRST_UNSAFE_ANYMODE locks in cooperative
// mode. A default Crst here would toggle cooperative->preemptive->acquire->cooperative,
// and the post-acquire DisablePreemptiveGC can block on a pending GC suspension,
// forming a deadlock cycle with threads waiting on the outer UNSAFE_ANYMODE lock.
// All data accessed under this lock is native (FILE*, fd, SString) so holding it
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// in cooperative mode does not introduce new GC-safety issues -- the I/O was already
// performed in cooperative mode with the previous default Crst.
s_csPerfMap.Init(CrstPerfMap, CrstFlags(CRST_UNSAFE_ANYMODE));

PerfMapType perfMapType = (PerfMapType)CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapEnabled);
PerfMap::Enable(perfMapType, false);
Expand Down Expand Up @@ -313,7 +321,7 @@ void PerfMap::LogJITCompiledMethod(MethodDesc * pMethod, PCODE pCode, size_t cod
CONTRACTL{
THROWS;
GC_NOTRIGGER;
MODE_PREEMPTIVE;
MODE_ANY;
PRECONDITION(pMethod != nullptr);
PRECONDITION(pCode != nullptr);
PRECONDITION(codeSize > 0);
Expand Down
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