[PATCH] D45398: Fix lock order inversion between ManagedStatic and Statistic
Bob Haarman via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Apr 17 16:40:29 PDT 2018
This revision was automatically updated to reflect the committed changes.
inglorion marked an inline comment as done.
Closed by commit rL330236: Fix lock order inversion between ManagedStatic and Statistic (authored by inglorion, committed by ).
Changed prior to commit:
https://reviews.llvm.org/D45398?vs=141697&id=142867#toc
Repository:
rL LLVM
https://reviews.llvm.org/D45398
Files:
llvm/trunk/lib/Support/Statistic.cpp
Index: llvm/trunk/lib/Support/Statistic.cpp
===================================================================
--- llvm/trunk/lib/Support/Statistic.cpp
+++ llvm/trunk/lib/Support/Statistic.cpp
@@ -94,10 +94,21 @@
void Statistic::RegisterStatistic() {
// If stats are enabled, inform StatInfo that this statistic should be
// printed.
- sys::SmartScopedLock<true> Writer(*StatLock);
+ // llvm_shutdown calls destructors while holding the ManagedStatic mutex.
+ // These destructors end up calling PrintStatistics, which takes StatLock.
+ // Since dereferencing StatInfo and StatLock can require taking the
+ // ManagedStatic mutex, doing so with StatLock held would lead to a lock
+ // order inversion. To avoid that, we dereference the ManagedStatics first,
+ // and only take StatLock afterwards.
if (!Initialized.load(std::memory_order_relaxed)) {
+ sys::SmartMutex<true> &Lock = *StatLock;
+ StatisticInfo &SI = *StatInfo;
+ sys::SmartScopedLock<true> Writer(Lock);
+ // Check Initialized again after acquiring the lock.
+ if (Initialized.load(std::memory_order_relaxed))
+ return;
if (Stats || Enabled)
- StatInfo->addStatistic(this);
+ SI.addStatistic(this);
// Remember we have been registered.
Initialized.store(true, std::memory_order_release);
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