Implement the "qSymbol" packet in order to be able to read queue information in debugserver and return the info in the stop reply packets.

A "qSymbol::" is sent when shared libraries have been loaded by hooking into the Process::ModulesDidLoad() function from within ProcessGDBRemote. This function was made virtual so that the ProcessGDBRemote version is called, which then first calls the Process::ModulesDidLoad(), and then it queries for any symbol lookups that the remote GDB server might want to do.

This allows debugserver to request the "dispatch_queue_offsets" symbol so that it can read the queue name, queue kind and queue serial number and include this data as part of the stop reply packet. Previously each thread would have to do 3 memory reads in order to read the queue name.

This is part of reducing the number of packets that are sent between LLDB and the remote GDB server.

<rdar://problem/21494354>

llvm-svn: 240466

1 files changed, 40 insertions, 7 deletions

diff --git a/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp b/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp
index e4108edc03f..e58121b1978 100644
--- a/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/ThreadGDBRemote.cpp
@@ -40,9 +40,11 @@ ThreadGDBRemote::ThreadGDBRemote (Process &process, lldb::tid_t tid) :
     Thread(process, tid),
     m_thread_name (),
     m_dispatch_queue_name (),
-    m_thread_dispatch_qaddr (LLDB_INVALID_ADDRESS)
+    m_thread_dispatch_qaddr (LLDB_INVALID_ADDRESS),
+    m_queue_kind(eQueueKindUnknown),
+    m_queue_serial(0)
 {
-    ProcessGDBRemoteLog::LogIf(GDBR_LOG_THREAD, "%p: ThreadGDBRemote::ThreadGDBRemote (pid = %i, tid = 0x%4.4x)", 
+    ProcessGDBRemoteLog::LogIf(GDBR_LOG_THREAD, "%p: ThreadGDBRemote::ThreadGDBRemote (pid = %i, tid = 0x%4.4x)",
                                this, 
                                process.GetID(),
                                GetID());
@@ -66,10 +68,36 @@ ThreadGDBRemote::GetName ()
     return m_thread_name.c_str();
 }
 
+void
+ThreadGDBRemote::ClearQueueInfo ()
+{
+    m_dispatch_queue_name.clear();
+    m_queue_kind = eQueueKindUnknown;
+    m_queue_serial = 0;
+}
+
+void
+ThreadGDBRemote::SetQueueInfo (std::string &&queue_name, QueueKind queue_kind, uint64_t queue_serial)
+{
+    m_dispatch_queue_name = queue_name;
+    m_queue_kind = queue_kind;
+    m_queue_serial = queue_serial;
+}
+
 
 const char *
 ThreadGDBRemote::GetQueueName ()
 {
+    // If our cached queue info is valid, then someone called ThreadGDBRemote::SetQueueInfo(...)
+    // with valid information that was gleaned from the stop reply packet. In this case we trust
+    // that the info is valid in m_dispatch_queue_name without refetching it
+    if (CachedQueueInfoIsValid())
+    {
+        if (m_dispatch_queue_name.empty())
+            return nullptr;
+        else
+            return m_dispatch_queue_name.c_str();
+    }
     // Always re-fetch the dispatch queue name since it can change
 
     if (m_thread_dispatch_qaddr != 0 || m_thread_dispatch_qaddr != LLDB_INVALID_ADDRESS)
@@ -79,13 +107,12 @@ ThreadGDBRemote::GetQueueName ()
         {
             SystemRuntime *runtime = process_sp->GetSystemRuntime ();
             if (runtime)
-            {
                 m_dispatch_queue_name = runtime->GetQueueNameFromThreadQAddress (m_thread_dispatch_qaddr);
-            }
-            if (m_dispatch_queue_name.length() > 0)
-            {
+            else
+                m_dispatch_queue_name.clear();
+
+            if (!m_dispatch_queue_name.empty())
                 return m_dispatch_queue_name.c_str();
-            }
         }
     }
     return NULL;
@@ -94,6 +121,12 @@ ThreadGDBRemote::GetQueueName ()
 queue_id_t
 ThreadGDBRemote::GetQueueID ()
 {
+    // If our cached queue info is valid, then someone called ThreadGDBRemote::SetQueueInfo(...)
+    // with valid information that was gleaned from the stop reply packet. In this case we trust
+    // that the info is valid in m_dispatch_queue_name without refetching it
+    if (CachedQueueInfoIsValid())
+        return m_queue_serial;
+
     if (m_thread_dispatch_qaddr != 0 || m_thread_dispatch_qaddr != LLDB_INVALID_ADDRESS)
     {
         ProcessSP process_sp (GetProcess());