1 files changed, 339 insertions, 0 deletions
diff --git a/xpcom/threads/BlockingResourceBase.h b/xpcom/threads/BlockingResourceBase.h
new file mode 100644
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+++ b/xpcom/threads/BlockingResourceBase.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_BlockingResourceBase_h
+#define mozilla_BlockingResourceBase_h
+
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/ThreadLocal.h"
+#include "mozilla/Attributes.h"
+
+#include "nscore.h"
+#include "nsDebug.h"
+
+#include "prtypes.h"
+
+#ifdef DEBUG
+
+// NB: Comment this out to enable callstack tracking.
+#  define MOZ_CALLSTACK_DISABLED
+
+#  include "prinit.h"
+
+#  ifndef MOZ_CALLSTACK_DISABLED
+#    include "mozilla/Maybe.h"
+#    include "nsTArray.h"
+#  endif
+
+#endif
+
+//
+// This header is not meant to be included by client code.
+//
+
+namespace mozilla {
+
+#ifdef DEBUG
+template <class T>
+class DeadlockDetector;
+#endif
+
+/**
+ * BlockingResourceBase
+ * Base class of resources that might block clients trying to acquire them.
+ * Does debugging and deadlock detection in DEBUG builds.
+ **/
+class BlockingResourceBase {
+ public:
+  // Needs to be kept in sync with kResourceTypeNames.
+  enum BlockingResourceType {
+    eMutex,
+    eReentrantMonitor,
+    eCondVar,
+    eRecursiveMutex
+  };
+
+  /**
+   * kResourceTypeName
+   * Human-readable version of BlockingResourceType enum.
+   */
+  static const char* const kResourceTypeName[];
+
+#ifdef DEBUG
+
+  static size_t SizeOfDeadlockDetector(MallocSizeOf aMallocSizeOf);
+
+  /**
+   * Print
+   * Write a description of this blocking resource to |aOut|.  If
+   * the resource appears to be currently acquired, the current
+   * acquisition context is printed and true is returned.
+   * Otherwise, we print the context from |aFirstSeen|, the
+   * first acquisition from which the code calling |Print()|
+   * became interested in us, and return false.
+   *
+   * *NOT* thread safe.  Reads |mAcquisitionContext| without
+   * synchronization, but this will not cause correctness
+   * problems.
+   *
+   * FIXME bug 456272: hack alert: because we can't write call
+   * contexts into strings, all info is written to stderr, but
+   * only some info is written into |aOut|
+   */
+  bool Print(nsACString& aOut) const;
+
+  size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
+    // NB: |mName| is not reported as it's expected to be a static string.
+    //     If we switch to a nsString it should be added to the tally.
+    //     |mChainPrev| is not reported because its memory is not owned.
+    size_t n = aMallocSizeOf(this);
+    return n;
+  }
+
+  // ``DDT'' = ``Deadlock Detector Type''
+  typedef DeadlockDetector<BlockingResourceBase> DDT;
+
+ protected:
+#  ifdef MOZ_CALLSTACK_DISABLED
+  typedef bool AcquisitionState;
+#  else
+  // Using maybe to use emplacement as the acquisition state flag; we may not
+  // always get a stack trace because of possible stack walk suppression or
+  // errors, hence can't use !IsEmpty() on the array itself as indication.
+  static size_t const kAcquisitionStateStackSize = 24;
+  typedef Maybe<AutoTArray<void*, kAcquisitionStateStackSize> >
+      AcquisitionState;
+#  endif
+
+  /**
+   * BlockingResourceBase
+   * Initialize this blocking resource.  Also hooks the resource into
+   * instrumentation code.
+   *
+   * Thread safe.
+   *
+   * @param aName A meaningful, unique name that can be used in
+   *              error messages, et al.
+   * @param aType The specific type of |this|, if any.
+   **/
+  BlockingResourceBase(const char* aName, BlockingResourceType aType);
+
+  ~BlockingResourceBase();
+
+  /**
+   * CheckAcquire
+   *
+   * Thread safe.
+   **/
+  void CheckAcquire();
+
+  /**
+   * Acquire
+   *
+   * *NOT* thread safe.  Requires ownership of underlying resource.
+   **/
+  void Acquire();  // NS_NEEDS_RESOURCE(this)
+
+  /**
+   * Release
+   * Remove this resource from the current thread's acquisition chain.
+   * The resource does not have to be at the front of the chain, although
+   * it is confusing to release resources in a different order than they
+   * are acquired.  This generates a warning.
+   *
+   * *NOT* thread safe.  Requires ownership of underlying resource.
+   **/
+  void Release();  // NS_NEEDS_RESOURCE(this)
+
+  /**
+   * ResourceChainFront
+   *
+   * Thread safe.
+   *
+   * @return the front of the resource acquisition chain, i.e., the last
+   *         resource acquired.
+   */
+  static BlockingResourceBase* ResourceChainFront() {
+    return sResourceAcqnChainFront.get();
+  }
+
+  /**
+   * ResourceChainPrev
+   *
+   * *NOT* thread safe.  Requires ownership of underlying resource.
+   */
+  static BlockingResourceBase* ResourceChainPrev(
+      const BlockingResourceBase* aResource) {
+    return aResource->mChainPrev;
+  }  // NS_NEEDS_RESOURCE(this)
+
+  /**
+   * ResourceChainAppend
+   * Set |this| to the front of the resource acquisition chain, and link
+   * |this| to |aPrev|.
+   *
+   * *NOT* thread safe.  Requires ownership of underlying resource.
+   */
+  void ResourceChainAppend(BlockingResourceBase* aPrev) {
+    mChainPrev = aPrev;
+    sResourceAcqnChainFront.set(this);
+  }  // NS_NEEDS_RESOURCE(this)
+
+  /**
+   * ResourceChainRemove
+   * Remove |this| from the front of the resource acquisition chain.
+   *
+   * *NOT* thread safe.  Requires ownership of underlying resource.
+   */
+  void ResourceChainRemove() {
+    NS_ASSERTION(this == ResourceChainFront(), "not at chain front");
+    sResourceAcqnChainFront.set(mChainPrev);
+  }  // NS_NEEDS_RESOURCE(this)
+
+  /**
+   * TakeAcquisitionState
+   * Return whether or not this resource was acquired and mark the resource
+   * as not acquired for subsequent uses.
+   *
+   * *NOT* thread safe.  Requires ownership of underlying resource.
+   */
+  AcquisitionState TakeAcquisitionState() {
+#  ifdef MOZ_CALLSTACK_DISABLED
+    bool acquired = mAcquired;
+    ClearAcquisitionState();
+    return acquired;
+#  else
+    return mAcquired.take();
+#  endif
+  }
+
+  /**
+   * SetAcquisitionState
+   * Set whether or not this resource was acquired.
+   *
+   * *NOT* thread safe.  Requires ownership of underlying resource.
+   */
+  void SetAcquisitionState(AcquisitionState&& aAcquisitionState) {
+    mAcquired = std::move(aAcquisitionState);
+  }
+
+  /**
+   * ClearAcquisitionState
+   * Indicate this resource is not acquired.
+   *
+   * *NOT* thread safe.  Requires ownership of underlying resource.
+   */
+  void ClearAcquisitionState() {
+#  ifdef MOZ_CALLSTACK_DISABLED
+    mAcquired = false;
+#  else
+    mAcquired.reset();
+#  endif
+  }
+
+  /**
+   * IsAcquired
+   * Indicates if this resource is acquired.
+   *
+   * *NOT* thread safe.  Requires ownership of underlying resource.
+   */
+  bool IsAcquired() const { return (bool)mAcquired; }
+
+  /**
+   * mChainPrev
+   * A series of resource acquisitions creates a chain of orders.  This
+   * chain is implemented as a linked list; |mChainPrev| points to the
+   * resource most recently Acquire()'d before this one.
+   **/
+  BlockingResourceBase* mChainPrev;
+
+ private:
+  /**
+   * mName
+   * A descriptive name for this resource.  Used in error
+   * messages etc.
+   */
+  const char* mName;
+
+  /**
+   * mType
+   * The more specific type of this resource.  Used to implement
+   * special semantics (e.g., reentrancy of monitors).
+   **/
+  BlockingResourceType mType;
+
+  /**
+   * mAcquired
+   * Indicates if this resource is currently acquired.
+   */
+  AcquisitionState mAcquired;
+
+#  ifndef MOZ_CALLSTACK_DISABLED
+  /**
+   * mFirstSeen
+   * Inidicates where this resource was first acquired.
+   */
+  AcquisitionState mFirstSeen;
+#  endif
+
+  /**
+   * sCallOnce
+   * Ensures static members are initialized only once, and in a
+   * thread-safe way.
+   */
+  static PRCallOnceType sCallOnce;
+
+  /**
+   * Thread-private pointer to the front of each thread's resource
+   * acquisition chain.
+   */
+  static MOZ_THREAD_LOCAL(BlockingResourceBase*) sResourceAcqnChainFront;
+
+  /**
+   * sDeadlockDetector
+   * Does as named.
+   */
+  static DDT* sDeadlockDetector;
+
+  /**
+   * InitStatics
+   * Inititialize static members of BlockingResourceBase that can't
+   * be statically initialized.
+   *
+   * *NOT* thread safe.
+   */
+  static PRStatus InitStatics();
+
+  /**
+   * Shutdown
+   * Free static members.
+   *
+   * *NOT* thread safe.
+   */
+  static void Shutdown();
+
+  static void StackWalkCallback(uint32_t aFrameNumber, void* aPc, void* aSp,
+                                void* aClosure);
+  static void GetStackTrace(AcquisitionState& aState,
+                            const void* aFirstFramePC);
+
+#  ifdef MOZILLA_INTERNAL_API
+  // so it can call BlockingResourceBase::Shutdown()
+  friend void LogTerm();
+#  endif  // ifdef MOZILLA_INTERNAL_API
+
+#else  // non-DEBUG implementation
+
+  BlockingResourceBase(const char* aName, BlockingResourceType aType) {}
+
+  ~BlockingResourceBase() {}
+
+#endif
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_BlockingResourceBase_h