Hi Greg,
If that is the case, then the main thread (i.e. the one running
Debugger::ExecuteIOHandler) needs to be blocked until the event arrives.
Why?
Because with the existing design once the user has entered their
"gdb-remote" command, and completed the connect call, the main thread
goes back to the IOHandlerEditline::Run() loop, sees that IsActive() is
true, prints the next prompt, etc.. When I debugged this I didn't see
any call to Deactivate or SetIsDone, which would have made IsActive
return false. (And then the async DefaultEventHandler awakes and it's
output "Process 1 stopped" splats over the prompt).
If the code is changed so that the edit line IOHandler's IsActive
returns false, while an asynchronous event is happening, then I think
that the main thread would spin, since the reader_sp->Run() function below:
void
Debugger::ExecuteIOHanders()
{
while (1)
{
IOHandlerSP reader_sp(m_input_reader_stack.Top());
if (!reader_sp)
break;
reader_sp->Activate();
reader_sp->Run();
reader_sp->Deactivate();
would immediately return. That's why I'm thinking the main thread
probably should block until the last issued command has completed.
Out of interest, I did research your "If someone is grabbing the event
manually by hijacking events" point. But when stopped state is detected
(i.e. the reply to ?) in GDBRemote and
Broadcaster::PrivateBroadcastEvent is called, there is no
hijacking_listener. Indeed the execution path is that as indicated by
the -->
if (hijacking_listener)
{
if (unique &&
hijacking_listener->PeekAtNextEventForBroadcasterWithType (this,
event_type))
return;
hijacking_listener->AddEvent (event_sp);
}
else
{
collection::iterator pos, end = m_listeners.end();
// Iterate through all listener/mask pairs
for (pos = m_listeners.begin(); pos != end; ++pos)
{
// If the listener's mask matches any bits that we just
set, then
// put the new event on its event queue.
if (event_type & pos->second)
{
if (unique &&
pos->first->PeekAtNextEventForBroadcasterWithType (this, event_type))
continue;
----> pos->first->AddEvent (event_sp);
So my contention is that in the case of gdb-connect the initial stop
state should either be delivered/printed sychronously in the
Process::ConnectRemote (i.e. in the mainthread context) or that the main
thread should block until either the event arrives, or for some other
reason the command last issued by the user is deemed to be "complete".
thanks
Matt
Greg Clayton wrote:
The event should get delivered to the Debugger thread that is waiting for
events and it should coordinate with the top io handler when printing it. If
someone is grabbing the event manually by hijacking events, then we need to fix
that code to send the event on to the unhijacked main event loop.
On Aug 20, 2014, at 1:42 AM, Matthew Gardiner <m...@csr.com> wrote:
Hi folks
I have been seeing another issue with the display of the lldb prompt. This time it's when I do "target
create elf-file", then "gdb-remote port-number". After the "gdb-remote" command I
see the fact that my process is stopped, e.g.
Process 1 stopped
on the screen. But no (lldb) prompt.
Some investigation revealed that what's *probably* happening is the main thread after
processing the "gdb-remote" returns to it's IOHandler, which then prints
(lldb). However, the inferior's state changes seem to delivered to stdout via a different
thread, basically one which sits in Debugger::DefaultEventHandler. This subsequent output
then, I think, overwrites the previous (lldb) prompt.
Now in my (and presumably other people's) situation, this issue is compounded by the
speed of the TCP/IP connection to the gdbserver stub, the "poll the hardware"
nature of my stub, and the fact the hardware is actually simulated - yes over a TCP/IP
socket.
FWIW, I resolved this by a horrible (POSIX only) hack, of sleeping for 300ms at
the bottom of the CommandInterpreter::HandleCommand function.
@@ -9,6 +9,8 @@
#include "lldb/lldb-python.h"
+#include <poll.h> // MG for prompt bugs
+
#include <string>
#include <vector>
#include <stdlib.h>
@@ -1916,6 +1918,9 @@
if (log)
log->Printf ("HandleCommand, command %s", (result.Succeeded() ? "succeeded" :
"did not succeed"));
+ // MG wait for remote connects etc. to complete
+ poll(0,0,300);
+
return result.Succeeded();
}
But this is horrid. Given this, and other prompt issues, I'm wondering whether
whether we need some brave soul, to redesign the current lldb IO handling
mechanisms.
Matt
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