Introduce a MainLoop class and switch llgs to use it

Summary:
This is the first part of our effort to make llgs single threaded. Currently, llgs consists of
about three threads and the synchronisation between them is a major source of latency when
debugging linux and android applications.

In order to be able to go single threaded, we must have the ability to listen for events from
multiple sources (primarily, client commands coming over the network and debug events from the
inferior) and perform necessary actions. For this reason I introduce the concept of a MainLoop.
A main loop has the ability to register callback's which will be invoked upon receipt of certain
events. MainLoopPosix has the ability to listen for file descriptors and signals.

For the moment, I have merely made the GDBRemoteCommunicationServerLLGS class use MainLoop
instead of waiting on the network socket directly, but the other threads still remain. In the
followup patches I indend to migrate NativeProcessLinux to this class and remove the remaining
threads.

Reviewers: ovyalov, clayborg, amccarth, zturner, emaste

Subscribers: tberghammer, lldb-commits

Differential Revision: http://reviews.llvm.org/D11066

llvm-svn: 242018

4 files changed, 71 insertions, 7 deletions

diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.cpp
index 13ce9b2dc5c..4ee66b84d47 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.cpp
@@ -132,7 +132,7 @@ GDBRemoteCommunicationServer::SendOKResponse ()
 }
 
 bool
-GDBRemoteCommunicationServer::HandshakeWithClient(Error *error_ptr)
+GDBRemoteCommunicationServer::HandshakeWithClient()
 {
     return GetAck() == PacketResult::Success;
 }
diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.h b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.h
index 992c6dffaf5..44c0f6a32f5 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.h
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServer.h
@@ -54,7 +54,7 @@ public:
     // After connecting, do a little handshake with the client to make sure
     // we are at least communicating
     bool
-    HandshakeWithClient (Error *error_ptr);
+    HandshakeWithClient ();
 
 protected:
     std::map<StringExtractorGDBRemote::ServerPacketType, PacketHandler> m_packet_handlers;
diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
index 5f0233b227b..c4523252f19 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
@@ -75,10 +75,11 @@ namespace
 // GDBRemoteCommunicationServerLLGS constructor
 //----------------------------------------------------------------------
 GDBRemoteCommunicationServerLLGS::GDBRemoteCommunicationServerLLGS(
-        const lldb::PlatformSP& platform_sp) :
+        const lldb::PlatformSP& platform_sp,
+        MainLoop &mainloop) :
     GDBRemoteCommunicationServerCommon ("gdb-remote.server", "gdb-remote.server.rx_packet"),
     m_platform_sp (platform_sp),
-    m_async_thread (LLDB_INVALID_HOST_THREAD),
+    m_mainloop (mainloop),
     m_current_tid (LLDB_INVALID_THREAD_ID),
     m_continue_tid (LLDB_INVALID_THREAD_ID),
     m_debugged_process_mutex (Mutex::eMutexTypeRecursive),
@@ -88,7 +89,8 @@ GDBRemoteCommunicationServerLLGS::GDBRemoteCommunicationServerLLGS(
     m_active_auxv_buffer_sp (),
     m_saved_registers_mutex (),
     m_saved_registers_map (),
-    m_next_saved_registers_id (1)
+    m_next_saved_registers_id (1),
+    m_handshake_completed (false)
 {
     assert(platform_sp);
     RegisterPacketHandlers();
@@ -782,6 +784,58 @@ GDBRemoteCommunicationServerLLGS::DidExec (NativeProcessProtocol *process)
     ClearProcessSpecificData ();
 }
 
+void
+GDBRemoteCommunicationServerLLGS::DataAvailableCallback ()
+{
+    Log *log (GetLogIfAnyCategoriesSet(GDBR_LOG_COMM));
+
+    if (! m_handshake_completed)
+    {
+        if (! HandshakeWithClient())
+        {
+            if(log)
+                log->Printf("GDBRemoteCommunicationServerLLGS::%s handshake with client failed, exiting",
+                        __FUNCTION__);
+            m_read_handle_up.reset();
+            m_mainloop.RequestTermination();
+            return;
+        }
+        m_handshake_completed = true;
+    }
+
+    bool interrupt = false;
+    bool done = false;
+    Error error;
+    while (true)
+    {
+        const PacketResult result = GetPacketAndSendResponse (0, error, interrupt, done);
+        if (result == PacketResult::ErrorReplyTimeout)
+            break; // No more packets in the queue
+
+        if ((result != PacketResult::Success))
+        {
+            if(log)
+                log->Printf("GDBRemoteCommunicationServerLLGS::%s processing a packet failed: %s",
+                        __FUNCTION__, error.AsCString());
+            m_read_handle_up.reset();
+            m_mainloop.RequestTermination();
+            break;
+        }
+    }
+}
+
+Error
+GDBRemoteCommunicationServerLLGS::InitializeConnection (std::unique_ptr<Connection> &&connection)
+{
+    IOObjectSP read_object_sp = connection->GetReadObject();
+    GDBRemoteCommunicationServer::SetConnection(connection.release());
+
+    Error error;
+    m_read_handle_up = m_mainloop.RegisterReadObject(read_object_sp,
+            [this] (MainLoopBase &) { DataAvailableCallback(); }, error);
+    return error;
+}
+
 GDBRemoteCommunication::PacketResult
 GDBRemoteCommunicationServerLLGS::SendONotification (const char *buffer, uint32_t len)
 {
diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h
index 1eda0b052bb..29f3fdebcfb 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h
@@ -19,6 +19,7 @@
 #include "lldb/Core/Communication.h"
 #include "lldb/Host/Mutex.h"
 #include "lldb/Host/common/NativeProcessProtocol.h"
+#include "lldb/Host/MainLoop.h"
 
 // Project includes
 #include "GDBRemoteCommunicationServerCommon.h"
@@ -26,6 +27,7 @@
 class StringExtractorGDBRemote;
 
 namespace lldb_private {
+
 namespace process_gdb_remote {
 
 class ProcessGDBRemote;
@@ -38,7 +40,7 @@ public:
     //------------------------------------------------------------------
     // Constructors and Destructors
     //------------------------------------------------------------------
-    GDBRemoteCommunicationServerLLGS(const lldb::PlatformSP& platform_sp);
+    GDBRemoteCommunicationServerLLGS(const lldb::PlatformSP& platform_sp, MainLoop &mainloop);
 
     virtual
     ~GDBRemoteCommunicationServerLLGS();
@@ -111,9 +113,13 @@ public:
     void
     DidExec (NativeProcessProtocol *process) override;
 
+    Error
+    InitializeConnection (std::unique_ptr<Connection> &&connection);
+
 protected:
     lldb::PlatformSP m_platform_sp;
-    lldb::thread_t m_async_thread;
+    MainLoop &m_mainloop;
+    MainLoop::ReadHandleUP m_read_handle_up;
     lldb::tid_t m_current_tid;
     lldb::tid_t m_continue_tid;
     Mutex m_debugged_process_mutex;
@@ -124,6 +130,7 @@ protected:
     Mutex m_saved_registers_mutex;
     std::unordered_map<uint32_t, lldb::DataBufferSP> m_saved_registers_map;
     uint32_t m_next_saved_registers_id;
+    bool m_handshake_completed : 1;
 
     PacketResult
     SendONotification (const char *buffer, uint32_t len);
@@ -295,6 +302,9 @@ private:
     void
     RegisterPacketHandlers ();
 
+    void
+    DataAvailableCallback ();
+
     //------------------------------------------------------------------
     // For GDBRemoteCommunicationServerLLGS only
     //------------------------------------------------------------------