[gem5-dev] Change in gem5/gem5[develop]: base: handle initial communication with GDB in `attach()`

[Jan Vrany (Gerrit) via gem5-dev]

Jan Vrany has uploaded this change for review. (  
https://gem5-review.googlesource.com/c/public/gem5/+/48182 )

Change subject: base: handle initial communication with GDB in `attach()`
......................................................................

base: handle initial communication with GDB in `attach()`

When remote GDB attaches to gem5, handle the initial communication
(`qSupported` and alike) right away instead of scheduling a `DataEvent`
and firing the simulation loop in hope that GDB will be quick enough to
send initial packets before instructions are dispatched.

This seems to fix the race described in 44612 [1]

[1]: https://gem5-review.googlesource.com/c/public/gem5/+/44612

Change-Id: I33b2922ba017205acabd51b6a8be3e6fb2d6409a
---
M src/base/remote_gdb.cc
M src/base/remote_gdb.hh
2 files changed, 6 insertions(+), 18 deletions(-)



diff --git a/src/base/remote_gdb.cc b/src/base/remote_gdb.cc
index 26aff5c..a6c569e 100644
--- a/src/base/remote_gdb.cc
+++ b/src/base/remote_gdb.cc
@@ -419,18 +419,19 @@
 {
     fd = f;

-    dataEvent = new DataEvent(this, fd, POLLIN);
-    pollQueue.schedule(dataEvent);
-
     attached = true;
     DPRINTFN("remote gdb attached\n");
+
+    processCommands();
+
+    dataEvent = new DataEvent(this, fd, POLLIN);
+    pollQueue.schedule(dataEvent);
 }

 void
 BaseRemoteGDB::detach()
 {
     attached = false;
-    active = false;
     clearSingleStep();
     close(fd);
     fd = -1;
@@ -496,19 +497,7 @@

     clearSingleStep();

-    /*
-     * The first entry to this function is normally through
-     * a breakpoint trap in kgdb_connect(), in which case we
-     * must advance past the breakpoint because gdb will not.
-     *
-     * On the first entry here, we expect that gdb is not yet
-     * listening to us, so just enter the interaction loop.
-     * After the debugger is "active" (connected) it will be
-     * waiting for a "signaled" message from us.
-     */
-    if (!active) {
-        active = true;
-    } else if (threadSwitching) {
+    if (threadSwitching) {
         threadSwitching = false;
         // Tell GDB the thread switch has completed.
         send("OK");
diff --git a/src/base/remote_gdb.hh b/src/base/remote_gdb.hh
index 6f57ae0..dbf3774 100644
--- a/src/base/remote_gdb.hh
+++ b/src/base/remote_gdb.hh
@@ -248,7 +248,6 @@
     /*
      * Simulator side debugger state.
      */
-    bool active = false;
     bool attached = false;
     bool threadSwitching = false;


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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: I33b2922ba017205acabd51b6a8be3e6fb2d6409a
Gerrit-Change-Number: 48182
Gerrit-PatchSet: 1
Gerrit-Owner: Jan Vrany <jan.vr...@labware.com>
Gerrit-MessageType: newchange
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