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

1 files changed, 37 insertions, 61 deletions

diff --git a/lldb/tools/lldb-server/lldb-gdbserver.cpp b/lldb/tools/lldb-server/lldb-gdbserver.cpp
index a286e3df0de..30bb2d68677 100644
--- a/lldb/tools/lldb-server/lldb-gdbserver.cpp
+++ b/lldb/tools/lldb-server/lldb-gdbserver.cpp
@@ -109,16 +109,21 @@ signal_handler(int signo)
     case SIGPIPE:
         g_sigpipe_received = 1;
         break;
-    case SIGHUP:
-        ++g_sighup_received_count;
-
-        // For now, swallow SIGHUP.
-        if (log)
-            log->Printf ("lldb-server:%s swallowing SIGHUP (receive count=%d)", __FUNCTION__, g_sighup_received_count);
-        signal (SIGHUP, signal_handler);
-        break;
     }
 }
+
+static void
+sighup_handler(MainLoopBase &mainloop)
+{
+    ++g_sighup_received_count;
+
+    Log *log (GetLogIfAnyCategoriesSet(LIBLLDB_LOG_PROCESS));
+    if (log)
+        log->Printf ("lldb-server:%s swallowing SIGHUP (receive count=%d)", __FUNCTION__, g_sighup_received_count);
+
+    if (g_sighup_received_count >= 2)
+        mainloop.RequestTermination();
+}
 #endif // #ifndef _WIN32
 
 static void
@@ -338,7 +343,7 @@ writePortToPipe(int unnamed_pipe_fd, const uint16_t port)
 }
 
 void
-ConnectToRemote(GDBRemoteCommunicationServerLLGS &gdb_server,
+ConnectToRemote(MainLoop &mainloop, GDBRemoteCommunicationServerLLGS &gdb_server,
         bool reverse_connect, const char *const host_and_port,
         const char *const progname, const char *const subcommand,
         const char *const named_pipe_path, int unnamed_pipe_fd)
@@ -372,6 +377,8 @@ ConnectToRemote(GDBRemoteCommunicationServerLLGS &gdb_server,
             exit (1);
         }
 
+        std::unique_ptr<ConnectionFileDescriptor> connection_up;
+
         if (reverse_connect)
         {
             // llgs will connect to the gdb-remote client.
@@ -388,8 +395,7 @@ ConnectToRemote(GDBRemoteCommunicationServerLLGS &gdb_server,
             snprintf(connection_url, sizeof(connection_url), "connect://%s", final_host_and_port.c_str ());
 
             // Create the connection.
-            std::unique_ptr<ConnectionFileDescriptor> connection_up (new ConnectionFileDescriptor ());
-            connection_up.reset (new ConnectionFileDescriptor ());
+            connection_up.reset(new ConnectionFileDescriptor);
             auto connection_result = connection_up->Connect (connection_url, &error);
             if (connection_result != eConnectionStatusSuccess)
             {
@@ -401,10 +407,6 @@ ConnectToRemote(GDBRemoteCommunicationServerLLGS &gdb_server,
                 fprintf (stderr, "error: failed to connect to client at '%s': %s", connection_url, error.AsCString ());
                 exit (-1);
             }
-
-            // We're connected.
-            printf ("Connection established.\n");
-            gdb_server.SetConnection (connection_up.release());
         }
         else
         {
@@ -461,10 +463,7 @@ ConnectToRemote(GDBRemoteCommunicationServerLLGS &gdb_server,
 
             // Ensure we connected.
             if (s_listen_connection_up)
-            {
-                printf ("Connection established '%s'\n", s_listen_connection_up->GetURI().c_str());
-                gdb_server.SetConnection (s_listen_connection_up.release());
-            }
+                connection_up = std::move(s_listen_connection_up);
             else
             {
                 fprintf (stderr, "failed to connect to '%s': %s\n", final_host_and_port.c_str (), error.AsCString ());
@@ -472,46 +471,13 @@ ConnectToRemote(GDBRemoteCommunicationServerLLGS &gdb_server,
                 exit (1);
             }
         }
-    }
-
-    if (gdb_server.IsConnected())
-    {
-        // After we connected, we need to get an initial ack from...
-        if (gdb_server.HandshakeWithClient(&error))
+        error = gdb_server.InitializeConnection (std::move(connection_up));
+        if (error.Fail())
         {
-            // We'll use a half a second timeout interval so that an exit conditions can
-            // be checked that often.
-            const uint32_t TIMEOUT_USEC = 500000;
-
-            bool interrupt = false;
-            bool done = false;
-            while (!interrupt && !done && (g_sighup_received_count < 2))
-            {
-                const GDBRemoteCommunication::PacketResult result = gdb_server.GetPacketAndSendResponse (TIMEOUT_USEC, error, interrupt, done);
-                if ((result != GDBRemoteCommunication::PacketResult::Success) &&
-                    (result != GDBRemoteCommunication::PacketResult::ErrorReplyTimeout))
-                {
-                    // We're bailing out - we only support successful handling and timeouts.
-                    fprintf(stderr, "leaving packet loop due to PacketResult %d\n", result);
-                    break;
-                }
-            }
-
-            if (error.Fail())
-            {
-                fprintf(stderr, "error: %s\n", error.AsCString());
-            }
-        }
-        else
-        {
-            fprintf(stderr, "error: handshake with client failed\n");
+            fprintf(stderr, "Failed to initialize connection: %s\n", error.AsCString());
+            exit(-1);
         }
-    }
-    else
-    {
-        fprintf (stderr, "no connection information provided, unable to run\n");
-        display_usage (progname, subcommand);
-        exit (1);
+        printf ("Connection established.\n");
     }
 }
 
@@ -521,10 +487,12 @@ ConnectToRemote(GDBRemoteCommunicationServerLLGS &gdb_server,
 int
 main_gdbserver (int argc, char *argv[])
 {
+    Error error;
+    MainLoop mainloop;
 #ifndef _WIN32
     // Setup signal handlers first thing.
     signal (SIGPIPE, signal_handler);
-    signal (SIGHUP, signal_handler);
+    MainLoop::SignalHandleUP sighup_handle = mainloop.RegisterSignal(SIGHUP, sighup_handler, error);
 #endif
 #ifdef __linux__
     // Block delivery of SIGCHLD on linux. NativeProcessLinux will read it using signalfd.
@@ -539,7 +507,6 @@ main_gdbserver (int argc, char *argv[])
     argc--;
     argv++;
     int long_option_index = 0;
-    Error error;
     int ch;
     std::string platform_name;
     std::string attach_target;
@@ -670,7 +637,7 @@ main_gdbserver (int argc, char *argv[])
     // Setup the platform that GDBRemoteCommunicationServerLLGS will use.
     lldb::PlatformSP platform_sp = setup_platform (platform_name);
 
-    GDBRemoteCommunicationServerLLGS gdb_server (platform_sp);
+    GDBRemoteCommunicationServerLLGS gdb_server (platform_sp, mainloop);
 
     const char *const host_and_port = argv[0];
     argc -= 1;
@@ -688,10 +655,19 @@ main_gdbserver (int argc, char *argv[])
     // Print version info.
     printf("%s-%s", LLGS_PROGRAM_NAME, LLGS_VERSION_STR);
 
-    ConnectToRemote(gdb_server, reverse_connect,
+    ConnectToRemote(mainloop, gdb_server, reverse_connect,
                     host_and_port, progname, subcommand,
                     named_pipe_path.c_str(), unnamed_pipe_fd);
 
+
+    if (! gdb_server.IsConnected())
+    {
+        fprintf (stderr, "no connection information provided, unable to run\n");
+        display_usage (progname, subcommand);
+        return 1;
+    }
+
+    mainloop.Run();
     fprintf(stderr, "lldb-server exiting...\n");
 
     return 0;