CrashGenerationServer's state machine can be invoked from both the application

thread and thread pool threads. This CL serializes access to the FSM state.
Handling of crash dump and client shutdown requests is still done
asynchronously.

Patch by Alex Pakhunov <alexeypa@chromium.org>

BUG=132164
TEST=remoting_unittests.BreakpadWinDeathTest.*

Review URL: https://breakpad.appspot.com/396002/


git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@970 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/client/windows/common/auto_critical_section.h

@@ -40,14 +40,31 @@ class AutoCriticalSection {
  public:
   // Creates a new instance with the given critical section object
   // and enters the critical section immediately.
-  explicit AutoCriticalSection(CRITICAL_SECTION* cs) : cs_(cs) {
+  explicit AutoCriticalSection(CRITICAL_SECTION* cs) : cs_(cs), taken_(false) {
     assert(cs_);
-    EnterCriticalSection(cs_);
+    Acquire();
   }
 
   // Destructor: leaves the critical section.
   ~AutoCriticalSection() {
+    if (taken_) {
+      Release();
+    }
+  }
+
+  // Enters the critical section. Recursive Acquire() calls are not allowed.
+  void Acquire() {
+    assert(!taken_);
+    EnterCriticalSection(cs_);
+    taken_ = true;
+  }
+
+  // Leaves the critical section. The caller should not call Release() unless
+  // the critical seciton has been entered already.
+  void Release() {
+    assert(taken_);
     LeaveCriticalSection(cs_);
+    taken_ = false;
   }
 
  private:
@@ -56,6 +73,7 @@ class AutoCriticalSection {
   AutoCriticalSection& operator=(const AutoCriticalSection&);
 
   CRITICAL_SECTION* cs_;
+  bool taken_;
 };
 
 }  // namespace google_breakpad

src/client/windows/crash_generation/crash_generation_server.cc

@@ -125,7 +125,7 @@ CrashGenerationServer::CrashGenerationServer(
       overlapped_(),
       client_info_(NULL),
       cleanup_item_count_(0) {
-  InitializeCriticalSection(&clients_sync_);
+  InitializeCriticalSection(&sync_);
 
   if (dump_path) {
     dump_generator_.reset(new MinidumpGenerator(*dump_path));
@@ -133,38 +133,41 @@ CrashGenerationServer::CrashGenerationServer(
 }
 
 CrashGenerationServer::~CrashGenerationServer() {
-  // Indicate to existing threads that server is shutting down.
+  // New scope to release the lock automatically.
-  shutting_down_ = true;
-
-  // Even if there are no current worker threads running, it is possible that
-  // an I/O request is pending on the pipe right now but not yet done. In fact,
-  // it's very likely this is the case unless we are in an ERROR state. If we
-  // don't wait for the pending I/O to be done, then when the I/O completes,
-  // it may write to invalid memory. AppVerifier will flag this problem too.
-  // So we disconnect from the pipe and then wait for the server to get into
-  // error state so that the pending I/O will fail and get cleared.
-  DisconnectNamedPipe(pipe_);
-  int num_tries = 100;
-  while (num_tries-- && server_state_ != IPC_SERVER_STATE_ERROR) {
-    Sleep(10);
-  }
-
-  // Unregister wait on the pipe.
-  if (pipe_wait_handle_) {
-    // Wait for already executing callbacks to finish.
-    UnregisterWaitEx(pipe_wait_handle_, INVALID_HANDLE_VALUE);
-  }
-
-  // Close the pipe to avoid further client connections.
-  if (pipe_) {
-    CloseHandle(pipe_);
-  }
-
-  // Request all ClientInfo objects to unregister all waits.
-  // New scope to hold the lock for the shortest time.
   {
-    AutoCriticalSection lock(&clients_sync_);
+    AutoCriticalSection lock(&sync_);
 
+    // Indicate to existing threads that server is shutting down.
+    shutting_down_ = true;
+
+    // Even if there are no current worker threads running, it is possible that
+    // an I/O request is pending on the pipe right now but not yet done.
+    // In fact, it's very likely this is the case unless we are in an ERROR
+    // state. If we don't wait for the pending I/O to be done, then when the I/O
+    // completes, it may write to invalid memory. AppVerifier will flag this
+    // problem too. So we disconnect from the pipe and then wait for the server
+    // to get into error state so that the pending I/O will fail and get
+    // cleared.
+    DisconnectNamedPipe(pipe_);
+    int num_tries = 100;
+    while (num_tries-- && server_state_ != IPC_SERVER_STATE_ERROR) {
+      lock.Release();
+      Sleep(10);
+      lock.Acquire();
+    }
+
+    // Unregister wait on the pipe.
+    if (pipe_wait_handle_) {
+      // Wait for already executing callbacks to finish.
+      UnregisterWaitEx(pipe_wait_handle_, INVALID_HANDLE_VALUE);
+    }
+
+    // Close the pipe to avoid further client connections.
+    if (pipe_) {
+      CloseHandle(pipe_);
+    }
+
+    // Request all ClientInfo objects to unregister all waits.
     std::list<ClientInfo*>::iterator iter;
     for (iter = clients_.begin(); iter != clients_.end(); ++iter) {
       ClientInfo* client_info = *iter;
@@ -185,33 +188,35 @@ CrashGenerationServer::~CrashGenerationServer() {
     }
   }
 
-  // Clean up all the ClientInfo objects.
   // New scope to hold the lock for the shortest time.
   {
-    AutoCriticalSection lock(&clients_sync_);
+    AutoCriticalSection lock(&sync_);
 
+    // Clean up all the ClientInfo objects.
     std::list<ClientInfo*>::iterator iter;
     for (iter = clients_.begin(); iter != clients_.end(); ++iter) {
       ClientInfo* client_info = *iter;
       delete client_info;
     }
+
+    if (server_alive_handle_) {
+      // Release the mutex before closing the handle so that clients requesting
+      // dumps wait for a long time for the server to generate a dump.
+      ReleaseMutex(server_alive_handle_);
+      CloseHandle(server_alive_handle_);
+    }
+
+    if (overlapped_.hEvent) {
+      CloseHandle(overlapped_.hEvent);
+    }
   }
 
-  if (server_alive_handle_) {
+  DeleteCriticalSection(&sync_);
-    // Release the mutex before closing the handle so that clients requesting
-    // dumps wait for a long time for the server to generate a dump.
-    ReleaseMutex(server_alive_handle_);
-    CloseHandle(server_alive_handle_);
-  }
-
-  if (overlapped_.hEvent) {
-    CloseHandle(overlapped_.hEvent);
-  }
-
-  DeleteCriticalSection(&clients_sync_);
 }
 
 bool CrashGenerationServer::Start() {
+  AutoCriticalSection lock(&sync_);
+
   if (server_state_ != IPC_SERVER_STATE_UNINITIALIZED) {
     return false;
   }
@@ -682,6 +687,8 @@ bool CrashGenerationServer::RespondToClient(ClientInfo* client_info) {
 // implements the state machine described in ReadMe.txt along with the
 // helper methods HandleXXXState.
 void CrashGenerationServer::HandleConnectionRequest() {
+  AutoCriticalSection lock(&sync_);
+
   // If we are shutting doen then get into ERROR state, reset the event so more
   // workers don't run and return immediately.
   if (shutting_down_) {
@@ -768,7 +775,7 @@ bool CrashGenerationServer::AddClient(ClientInfo* client_info) {
 
   // New scope to hold the lock for the shortest time.
   {
-    AutoCriticalSection lock(&clients_sync_);
+    AutoCriticalSection lock(&sync_);
     clients_.push_back(client_info);
   }
 
@@ -836,7 +843,7 @@ void CrashGenerationServer::DoCleanup(ClientInfo* client_info) {
 
   // Start a new scope to release lock automatically.
   {
-    AutoCriticalSection lock(&clients_sync_);
+    AutoCriticalSection lock(&sync_);
     clients_.remove(client_info);
   }
 

src/client/windows/crash_generation/crash_generation_server.h

@@ -216,8 +216,9 @@ class CrashGenerationServer {
   // asynchronous IO operation.
   void EnterStateWhenSignaled(IPCServerState state);
 
-  // Sync object for thread-safe access to the shared list of clients.
+  // Sync object for thread-safe access to the shared list of clients and
-  CRITICAL_SECTION clients_sync_;
+  // the server's state.
+  CRITICAL_SECTION sync_;
 
   // List of clients.
   std::list<ClientInfo*> clients_;
@@ -271,10 +272,10 @@ class CrashGenerationServer {
   // Note that since we restrict the pipe to one instance, we
   // only need to keep one state of the server. Otherwise, server
   // would have one state per client it is talking to.
-  volatile IPCServerState server_state_;
+  IPCServerState server_state_;
 
   // Whether the server is shutting down.
-  volatile bool shutting_down_;
+  bool shutting_down_;
 
   // Overlapped instance for async I/O on the pipe.
   OVERLAPPED overlapped_;