1 files changed, 547 insertions, 0 deletions
diff --git a/xpcom/threads/BlockingResourceBase.cpp b/xpcom/threads/BlockingResourceBase.cpp
new file mode 100644
index 0000000000..c2ba82e07a
--- /dev/null
+++ b/xpcom/threads/BlockingResourceBase.cpp
@@ -0,0 +1,547 @@
+/* -*- 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/. */
+
+#include "mozilla/BlockingResourceBase.h"
+
+#ifdef DEBUG
+#  include "prthread.h"
+
+#  ifndef MOZ_CALLSTACK_DISABLED
+#    include "CodeAddressService.h"
+#    include "nsHashKeys.h"
+#    include "mozilla/StackWalk.h"
+#    include "nsTHashtable.h"
+#  endif
+
+#  include "mozilla/Attributes.h"
+#  include "mozilla/CondVar.h"
+#  include "mozilla/DeadlockDetector.h"
+#  include "mozilla/RecursiveMutex.h"
+#  include "mozilla/ReentrantMonitor.h"
+#  include "mozilla/Mutex.h"
+#  include "mozilla/RWLock.h"
+#  include "mozilla/UniquePtr.h"
+
+#  if defined(MOZILLA_INTERNAL_API)
+#    include "mozilla/ProfilerThreadSleep.h"
+#  endif  // MOZILLA_INTERNAL_API
+
+#endif  // ifdef DEBUG
+
+namespace mozilla {
+//
+// BlockingResourceBase implementation
+//
+
+// static members
+const char* const BlockingResourceBase::kResourceTypeName[] = {
+    // needs to be kept in sync with BlockingResourceType
+    "Mutex", "ReentrantMonitor", "CondVar", "RecursiveMutex"};
+
+#ifdef DEBUG
+
+PRCallOnceType BlockingResourceBase::sCallOnce;
+MOZ_THREAD_LOCAL(BlockingResourceBase*)
+BlockingResourceBase::sResourceAcqnChainFront;
+BlockingResourceBase::DDT* BlockingResourceBase::sDeadlockDetector;
+
+void BlockingResourceBase::StackWalkCallback(uint32_t aFrameNumber, void* aPc,
+                                             void* aSp, void* aClosure) {
+#  ifndef MOZ_CALLSTACK_DISABLED
+  AcquisitionState* state = (AcquisitionState*)aClosure;
+  state->ref().AppendElement(aPc);
+#  endif
+}
+
+void BlockingResourceBase::GetStackTrace(AcquisitionState& aState,
+                                         const void* aFirstFramePC) {
+#  ifndef MOZ_CALLSTACK_DISABLED
+  // Clear the array...
+  aState.reset();
+  // ...and create a new one; this also puts the state to 'acquired' status
+  // regardless of whether we obtain a stack trace or not.
+  aState.emplace();
+
+  MozStackWalk(StackWalkCallback, aFirstFramePC, kAcquisitionStateStackSize,
+               aState.ptr());
+#  endif
+}
+
+/**
+ * PrintCycle
+ * Append to |aOut| detailed information about the circular
+ * dependency in |aCycle|.  Returns true if it *appears* that this
+ * cycle may represent an imminent deadlock, but this is merely a
+ * heuristic; the value returned may be a false positive or false
+ * negative.
+ *
+ * *NOT* thread safe.  Calls |Print()|.
+ *
+ * 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|
+ */
+static bool PrintCycle(
+    const BlockingResourceBase::DDT::ResourceAcquisitionArray& aCycle,
+    nsACString& aOut) {
+  NS_ASSERTION(aCycle.Length() > 1, "need > 1 element for cycle!");
+
+  bool maybeImminent = true;
+
+  fputs("=== Cyclical dependency starts at\n", stderr);
+  aOut += "Cyclical dependency starts at\n";
+
+  const BlockingResourceBase::DDT::ResourceAcquisitionArray::value_type res =
+      aCycle.ElementAt(0);
+  maybeImminent &= res->Print(aOut);
+
+  BlockingResourceBase::DDT::ResourceAcquisitionArray::index_type i;
+  BlockingResourceBase::DDT::ResourceAcquisitionArray::size_type len =
+      aCycle.Length();
+  const BlockingResourceBase::DDT::ResourceAcquisitionArray::value_type* it =
+      1 + aCycle.Elements();
+  for (i = 1; i < len - 1; ++i, ++it) {
+    fputs("\n--- Next dependency:\n", stderr);
+    aOut += "\nNext dependency:\n";
+
+    maybeImminent &= (*it)->Print(aOut);
+  }
+
+  fputs("\n=== Cycle completed at\n", stderr);
+  aOut += "Cycle completed at\n";
+  (*it)->Print(aOut);
+
+  return maybeImminent;
+}
+
+bool BlockingResourceBase::Print(nsACString& aOut) const {
+  fprintf(stderr, "--- %s : %s", kResourceTypeName[mType], mName);
+  aOut += BlockingResourceBase::kResourceTypeName[mType];
+  aOut += " : ";
+  aOut += mName;
+
+  bool acquired = IsAcquired();
+
+  if (acquired) {
+    fputs(" (currently acquired)\n", stderr);
+    aOut += " (currently acquired)\n";
+  }
+
+  fputs(" calling context\n", stderr);
+#  ifdef MOZ_CALLSTACK_DISABLED
+  fputs("  [stack trace unavailable]\n", stderr);
+#  else
+  const AcquisitionState& state = acquired ? mAcquired : mFirstSeen;
+
+  CodeAddressService<> addressService;
+
+  for (uint32_t i = 0; i < state.ref().Length(); i++) {
+    const size_t kMaxLength = 1024;
+    char buffer[kMaxLength];
+    addressService.GetLocation(i + 1, state.ref()[i], buffer, kMaxLength);
+    const char* fmt = "    %s\n";
+    aOut.AppendLiteral("    ");
+    aOut.Append(buffer);
+    aOut.AppendLiteral("\n");
+    fprintf(stderr, fmt, buffer);
+  }
+
+#  endif
+
+  return acquired;
+}
+
+BlockingResourceBase::BlockingResourceBase(
+    const char* aName, BlockingResourceBase::BlockingResourceType aType)
+    : mName(aName),
+      mType(aType)
+#  ifdef MOZ_CALLSTACK_DISABLED
+      ,
+      mAcquired(false)
+#  else
+      ,
+      mAcquired()
+#  endif
+{
+  MOZ_ASSERT(mName, "Name must be nonnull");
+  // PR_CallOnce guaranatees that InitStatics is called in a
+  // thread-safe way
+  if (PR_SUCCESS != PR_CallOnce(&sCallOnce, InitStatics)) {
+    MOZ_CRASH("can't initialize blocking resource static members");
+  }
+
+  mChainPrev = 0;
+  sDeadlockDetector->Add(this);
+}
+
+BlockingResourceBase::~BlockingResourceBase() {
+  // we don't check for really obviously bad things like freeing
+  // Mutexes while they're still locked.  it is assumed that the
+  // base class, or its underlying primitive, will check for such
+  // stupid mistakes.
+  mChainPrev = 0;  // racy only for stupidly buggy client code
+  if (sDeadlockDetector) {
+    sDeadlockDetector->Remove(this);
+  }
+}
+
+size_t BlockingResourceBase::SizeOfDeadlockDetector(
+    MallocSizeOf aMallocSizeOf) {
+  return sDeadlockDetector
+             ? sDeadlockDetector->SizeOfIncludingThis(aMallocSizeOf)
+             : 0;
+}
+
+PRStatus BlockingResourceBase::InitStatics() {
+  MOZ_ASSERT(sResourceAcqnChainFront.init());
+  sDeadlockDetector = new DDT();
+  if (!sDeadlockDetector) {
+    MOZ_CRASH("can't allocate deadlock detector");
+  }
+  return PR_SUCCESS;
+}
+
+void BlockingResourceBase::Shutdown() {
+  delete sDeadlockDetector;
+  sDeadlockDetector = 0;
+}
+
+MOZ_NEVER_INLINE void BlockingResourceBase::CheckAcquire() {
+  if (mType == eCondVar) {
+    MOZ_ASSERT_UNREACHABLE(
+        "FIXME bug 456272: annots. to allow CheckAcquire()ing condvars");
+    return;
+  }
+
+  BlockingResourceBase* chainFront = ResourceChainFront();
+  mozilla::UniquePtr<DDT::ResourceAcquisitionArray> cycle(
+      sDeadlockDetector->CheckAcquisition(chainFront ? chainFront : 0, this));
+  if (!cycle) {
+    return;
+  }
+
+#  ifndef MOZ_CALLSTACK_DISABLED
+  // Update the current stack before printing.
+  GetStackTrace(mAcquired, CallerPC());
+#  endif
+
+  fputs("###!!! ERROR: Potential deadlock detected:\n", stderr);
+  nsAutoCString out("Potential deadlock detected:\n");
+  bool maybeImminent = PrintCycle(*cycle, out);
+
+  if (maybeImminent) {
+    fputs("\n###!!! Deadlock may happen NOW!\n\n", stderr);
+    out.AppendLiteral("\n###!!! Deadlock may happen NOW!\n\n");
+  } else {
+    fputs("\nDeadlock may happen for some other execution\n\n", stderr);
+    out.AppendLiteral("\nDeadlock may happen for some other execution\n\n");
+  }
+
+  // Only error out if we think a deadlock is imminent.
+  if (maybeImminent) {
+    NS_ERROR(out.get());
+  } else {
+    NS_WARNING(out.get());
+  }
+}
+
+MOZ_NEVER_INLINE void BlockingResourceBase::Acquire() {
+  if (mType == eCondVar) {
+    MOZ_ASSERT_UNREACHABLE(
+        "FIXME bug 456272: annots. to allow Acquire()ing condvars");
+    return;
+  }
+  NS_ASSERTION(!IsAcquired(), "reacquiring already acquired resource");
+
+  ResourceChainAppend(ResourceChainFront());
+
+#  ifdef MOZ_CALLSTACK_DISABLED
+  mAcquired = true;
+#  else
+  // Take a stack snapshot.
+  GetStackTrace(mAcquired, CallerPC());
+  MOZ_ASSERT(IsAcquired());
+
+  if (!mFirstSeen) {
+    mFirstSeen = mAcquired.map(
+        [](AcquisitionState::ValueType& state) { return state.Clone(); });
+  }
+#  endif
+}
+
+void BlockingResourceBase::Release() {
+  if (mType == eCondVar) {
+    MOZ_ASSERT_UNREACHABLE(
+        "FIXME bug 456272: annots. to allow Release()ing condvars");
+    return;
+  }
+
+  BlockingResourceBase* chainFront = ResourceChainFront();
+  NS_ASSERTION(chainFront && IsAcquired(),
+               "Release()ing something that hasn't been Acquire()ed");
+
+  if (chainFront == this) {
+    ResourceChainRemove();
+  } else {
+    // remove this resource from wherever it lives in the chain
+    // we walk backwards in order of acquisition:
+    //  (1)  ...node<-prev<-curr...
+    //              /     /
+    //  (2)  ...prev<-curr...
+    BlockingResourceBase* curr = chainFront;
+    BlockingResourceBase* prev = nullptr;
+    while (curr && (prev = curr->mChainPrev) && (prev != this)) {
+      curr = prev;
+    }
+    if (prev == this) {
+      curr->mChainPrev = prev->mChainPrev;
+    }
+  }
+
+  ClearAcquisitionState();
+}
+
+//
+// Debug implementation of (OffTheBooks)Mutex
+void OffTheBooksMutex::Lock() {
+  CheckAcquire();
+  this->lock();
+  mOwningThread = PR_GetCurrentThread();
+  Acquire();
+}
+
+bool OffTheBooksMutex::TryLock() {
+  bool locked = this->tryLock();
+  if (locked) {
+    mOwningThread = PR_GetCurrentThread();
+    Acquire();
+  }
+  return locked;
+}
+
+void OffTheBooksMutex::Unlock() {
+  Release();
+  mOwningThread = nullptr;
+  this->unlock();
+}
+
+void OffTheBooksMutex::AssertCurrentThreadOwns() const {
+  MOZ_ASSERT(IsAcquired() && mOwningThread == PR_GetCurrentThread());
+}
+
+//
+// Debug implementation of RWLock
+//
+
+bool RWLock::TryReadLock() {
+  bool locked = this->detail::RWLockImpl::tryReadLock();
+  MOZ_ASSERT_IF(locked, mOwningThread == nullptr);
+  return locked;
+}
+
+void RWLock::ReadLock() {
+  // All we want to ensure here is that we're not attempting to acquire the
+  // read lock while this thread is holding the write lock.
+  CheckAcquire();
+  this->detail::RWLockImpl::readLock();
+  MOZ_ASSERT(mOwningThread == nullptr);
+}
+
+void RWLock::ReadUnlock() {
+  MOZ_ASSERT(mOwningThread == nullptr);
+  this->detail::RWLockImpl::readUnlock();
+}
+
+bool RWLock::TryWriteLock() {
+  bool locked = this->detail::RWLockImpl::tryWriteLock();
+  if (locked) {
+    mOwningThread = PR_GetCurrentThread();
+    Acquire();
+  }
+  return locked;
+}
+
+void RWLock::WriteLock() {
+  CheckAcquire();
+  this->detail::RWLockImpl::writeLock();
+  mOwningThread = PR_GetCurrentThread();
+  Acquire();
+}
+
+void RWLock::WriteUnlock() {
+  Release();
+  mOwningThread = nullptr;
+  this->detail::RWLockImpl::writeUnlock();
+}
+
+//
+// Debug implementation of ReentrantMonitor
+void ReentrantMonitor::Enter() {
+  BlockingResourceBase* chainFront = ResourceChainFront();
+
+  // the code below implements monitor reentrancy semantics
+
+  if (this == chainFront) {
+    // immediately re-entered the monitor: acceptable
+    PR_EnterMonitor(mReentrantMonitor);
+    ++mEntryCount;
+    return;
+  }
+
+  // this is sort of a hack around not recording the thread that
+  // owns this monitor
+  if (chainFront) {
+    for (BlockingResourceBase* br = ResourceChainPrev(chainFront); br;
+         br = ResourceChainPrev(br)) {
+      if (br == this) {
+        NS_WARNING(
+            "Re-entering ReentrantMonitor after acquiring other resources.");
+
+        // show the caller why this is potentially bad
+        CheckAcquire();
+
+        PR_EnterMonitor(mReentrantMonitor);
+        ++mEntryCount;
+        return;
+      }
+    }
+  }
+
+  CheckAcquire();
+  PR_EnterMonitor(mReentrantMonitor);
+  NS_ASSERTION(mEntryCount == 0, "ReentrantMonitor isn't free!");
+  Acquire();  // protected by mReentrantMonitor
+  mEntryCount = 1;
+}
+
+void ReentrantMonitor::Exit() {
+  if (--mEntryCount == 0) {
+    Release();  // protected by mReentrantMonitor
+  }
+  PRStatus status = PR_ExitMonitor(mReentrantMonitor);
+  NS_ASSERTION(PR_SUCCESS == status, "bad ReentrantMonitor::Exit()");
+}
+
+nsresult ReentrantMonitor::Wait(PRIntervalTime aInterval) {
+  AssertCurrentThreadIn();
+
+  // save monitor state and reset it to empty
+  int32_t savedEntryCount = mEntryCount;
+  AcquisitionState savedAcquisitionState = TakeAcquisitionState();
+  BlockingResourceBase* savedChainPrev = mChainPrev;
+  mEntryCount = 0;
+  mChainPrev = 0;
+
+  nsresult rv;
+  {
+#  if defined(MOZILLA_INTERNAL_API)
+    AUTO_PROFILER_THREAD_SLEEP;
+#  endif
+    // give up the monitor until we're back from Wait()
+    rv = PR_Wait(mReentrantMonitor, aInterval) == PR_SUCCESS ? NS_OK
+                                                             : NS_ERROR_FAILURE;
+  }
+
+  // restore saved state
+  mEntryCount = savedEntryCount;
+  SetAcquisitionState(std::move(savedAcquisitionState));
+  mChainPrev = savedChainPrev;
+
+  return rv;
+}
+
+//
+// Debug implementation of RecursiveMutex
+void RecursiveMutex::Lock() {
+  BlockingResourceBase* chainFront = ResourceChainFront();
+
+  // the code below implements mutex reentrancy semantics
+
+  if (this == chainFront) {
+    // immediately re-entered the mutex: acceptable
+    LockInternal();
+    ++mEntryCount;
+    return;
+  }
+
+  // this is sort of a hack around not recording the thread that
+  // owns this monitor
+  if (chainFront) {
+    for (BlockingResourceBase* br = ResourceChainPrev(chainFront); br;
+         br = ResourceChainPrev(br)) {
+      if (br == this) {
+        NS_WARNING(
+            "Re-entering RecursiveMutex after acquiring other resources.");
+
+        // show the caller why this is potentially bad
+        CheckAcquire();
+
+        LockInternal();
+        ++mEntryCount;
+        return;
+      }
+    }
+  }
+
+  CheckAcquire();
+  LockInternal();
+  NS_ASSERTION(mEntryCount == 0, "RecursiveMutex isn't free!");
+  Acquire();  // protected by us
+  mOwningThread = PR_GetCurrentThread();
+  mEntryCount = 1;
+}
+
+void RecursiveMutex::Unlock() {
+  if (--mEntryCount == 0) {
+    Release();  // protected by us
+    mOwningThread = nullptr;
+  }
+  UnlockInternal();
+}
+
+void RecursiveMutex::AssertCurrentThreadIn() const {
+  MOZ_ASSERT(IsAcquired() && mOwningThread == PR_GetCurrentThread());
+}
+
+//
+// Debug implementation of CondVar
+void OffTheBooksCondVar::Wait() {
+  // Forward to the timed version of OffTheBooksCondVar::Wait to avoid code
+  // duplication.
+  CVStatus status = Wait(TimeDuration::Forever());
+  MOZ_ASSERT(status == CVStatus::NoTimeout);
+}
+
+CVStatus OffTheBooksCondVar::Wait(TimeDuration aDuration) {
+  AssertCurrentThreadOwnsMutex();
+
+  // save mutex state and reset to empty
+  AcquisitionState savedAcquisitionState = mLock->TakeAcquisitionState();
+  BlockingResourceBase* savedChainPrev = mLock->mChainPrev;
+  PRThread* savedOwningThread = mLock->mOwningThread;
+  mLock->mChainPrev = 0;
+  mLock->mOwningThread = nullptr;
+
+  // give up mutex until we're back from Wait()
+  CVStatus status;
+  {
+#  if defined(MOZILLA_INTERNAL_API)
+    AUTO_PROFILER_THREAD_SLEEP;
+#  endif
+    status = mImpl.wait_for(*mLock, aDuration);
+  }
+
+  // restore saved state
+  mLock->SetAcquisitionState(std::move(savedAcquisitionState));
+  mLock->mChainPrev = savedChainPrev;
+  mLock->mOwningThread = savedOwningThread;
+
+  return status;
+}
+
+#endif  // ifdef DEBUG
+
+}  // namespace mozilla