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diff --git a/lib/StaticAnalyzer/Checkers/BlockInCriticalSectionChecker.cpp b/lib/StaticAnalyzer/Checkers/BlockInCriticalSectionChecker.cpp
new file mode 100644
index 0000000000000..082a4873217b7
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+++ b/lib/StaticAnalyzer/Checkers/BlockInCriticalSectionChecker.cpp
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+//===-- BlockInCriticalSectionChecker.cpp -----------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Defines a checker for blocks in critical sections. This checker should find
+// the calls to blocking functions (for example: sleep, getc, fgets, read,
+// recv etc.) inside a critical section. When sleep(x) is called while a mutex
+// is held, other threades cannot lock the same mutex. This might take some
+// time, leading to bad performance or even deadlock.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ClangSACheckers.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+
+class BlockInCriticalSectionChecker : public Checker<check::PostCall,
+                                                     check::PreCall> {
+
+  CallDescription LockFn, UnlockFn, SleepFn, GetcFn, FgetsFn, ReadFn, RecvFn;
+
+  std::unique_ptr<BugType> BlockInCritSectionBugType;
+
+  void reportBlockInCritSection(SymbolRef FileDescSym,
+                                const CallEvent &call,
+                                CheckerContext &C) const;
+
+public:
+  BlockInCriticalSectionChecker();
+
+  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
+
+  /// Process unlock.
+  /// Process lock.
+  /// Process blocking functions (sleep, getc, fgets, read, recv)
+  void checkPostCall(const CallEvent &Call, CheckerContext &C) const;
+
+};
+
+} // end anonymous namespace
+
+REGISTER_TRAIT_WITH_PROGRAMSTATE(MutexCounter, unsigned)
+
+BlockInCriticalSectionChecker::BlockInCriticalSectionChecker()
+    : LockFn("lock"), UnlockFn("unlock"), SleepFn("sleep"), GetcFn("getc"),
+      FgetsFn("fgets"), ReadFn("read"), RecvFn("recv") {
+  // Initialize the bug type.
+  BlockInCritSectionBugType.reset(
+      new BugType(this, "Call to blocking function in critical section",
+                        "Blocking Error"));
+}
+
+void BlockInCriticalSectionChecker::checkPreCall(const CallEvent &Call,
+                                                 CheckerContext &C) const {
+}
+
+void BlockInCriticalSectionChecker::checkPostCall(const CallEvent &Call,
+                                                  CheckerContext &C) const {
+  if (!Call.isCalled(LockFn)
+      && !Call.isCalled(SleepFn)
+      && !Call.isCalled(GetcFn)
+      && !Call.isCalled(FgetsFn)
+      && !Call.isCalled(ReadFn)
+      && !Call.isCalled(RecvFn)
+      && !Call.isCalled(UnlockFn))
+    return;
+
+  ProgramStateRef State = C.getState();
+  unsigned mutexCount = State->get<MutexCounter>();
+  if (Call.isCalled(UnlockFn) && mutexCount > 0) {
+    State = State->set<MutexCounter>(--mutexCount);
+    C.addTransition(State);
+  } else if (Call.isCalled(LockFn)) {
+    State = State->set<MutexCounter>(++mutexCount);
+    C.addTransition(State);
+  } else if (mutexCount > 0) {
+    SymbolRef BlockDesc = Call.getReturnValue().getAsSymbol();
+    reportBlockInCritSection(BlockDesc, Call, C);
+  }
+}
+
+void BlockInCriticalSectionChecker::reportBlockInCritSection(
+    SymbolRef BlockDescSym, const CallEvent &Call, CheckerContext &C) const {
+  ExplodedNode *ErrNode = C.generateNonFatalErrorNode();
+  if (!ErrNode)
+    return;
+
+  auto R = llvm::make_unique<BugReport>(*BlockInCritSectionBugType,
+      "A blocking function %s is called inside a critical section.", ErrNode);
+  R->addRange(Call.getSourceRange());
+  R->markInteresting(BlockDescSym);
+  C.emitReport(std::move(R));
+}
+
+void ento::registerBlockInCriticalSectionChecker(CheckerManager &mgr) {
+  mgr.registerChecker<BlockInCriticalSectionChecker>();
+}