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[LLGS] Don't forward I/O when process is stopped 

Summary:
This makes sure we do not attempt to send output over the gdb-remote protocol when the client is
not expecting it (i.e., after sending the stop-reply packet). Normally, this should not happen
(the process cannot generate output when it is stopped), but due to the fact that pty
communication is asynchronous in the linux kernel (llvm.org/pr25652), we may sometimes get this
output too late. Instead, we just hold the output, and send it next time we resume. This is not
ideal, but at least it makes sure we do not violate the remote protocol. Given that this happens
extremely rarely it's not worth trying to work around it with sleeps or something like that.

I also remove the m_stdio_communication_mutex, as all of LLGS is now single-threaded anyway.

Reviewers: tberghammer, ovyalov

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D15019

llvm-svn: 254200
This commit is contained in:
Pavel Labath 2015-11-27 13:33:29 +00:00
parent 97f4d2c47f
commit abadc22172
2 changed files with 46 additions and 29 deletions
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71
lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
View File

@ -44,6 +44,7 @@
#include "lldb/Host/common/NativeProcessProtocol.h"
#include "lldb/Host/common/NativeThreadProtocol.h"
#include "lldb/Utility/JSON.h"
#include "lldb/Utility/LLDBAssert.h"
// Project includes
#include "Utility/StringExtractorGDBRemote.h"
@ -860,21 +861,30 @@ GDBRemoteCommunicationServerLLGS::ProcessStateChanged (NativeProcessProtocol *pr
StateAsCString (state));
}
// Make sure we get all of the pending stdout/stderr from the inferior
// and send it to the lldb host before we send the state change
// notification
SendProcessOutput();
switch (state)
{
case StateType::eStateExited:
HandleInferiorState_Exited (process);
case StateType::eStateRunning:
StartSTDIOForwarding();
break;
case StateType::eStateStopped:
// Make sure we get all of the pending stdout/stderr from the inferior
// and send it to the lldb host before we send the state change
// notification
SendProcessOutput();
// Then stop the forwarding, so that any late output (see llvm.org/pr25652) does not
// interfere with our protocol.
StopSTDIOForwarding();
HandleInferiorState_Stopped (process);
break;
case StateType::eStateExited:
// Same as above
SendProcessOutput();
StopSTDIOForwarding();
HandleInferiorState_Exited (process);
break;
default:
if (log)
{
@ -975,7 +985,6 @@ GDBRemoteCommunicationServerLLGS::SetSTDIOFileDescriptor (int fd)
return error;
}
Mutex::Locker locker(m_stdio_communication_mutex);
m_stdio_communication.SetCloseOnEOF (false);
m_stdio_communication.SetConnection (conn_up.release());
if (!m_stdio_communication.IsConnected ())
@ -984,33 +993,42 @@ GDBRemoteCommunicationServerLLGS::SetSTDIOFileDescriptor (int fd)
return error;
}
return Error();
}
void
GDBRemoteCommunicationServerLLGS::StartSTDIOForwarding()
{
// Don't forward if not connected (e.g. when attaching).
if (! m_stdio_communication.IsConnected())
return;
// llgs local-process debugging may specify PTY paths, which will make these
// file actions non-null
// process launch -e/o will also make these file actions non-null
// nullptr means that the traffic is expected to flow over gdb-remote protocol
if (
m_process_launch_info.GetFileActionForFD(STDOUT_FILENO) == nullptr ||
m_process_launch_info.GetFileActionForFD(STDERR_FILENO) == nullptr
)
{
// output from the process must be forwarded over gdb-remote
m_stdio_handle_up = m_mainloop.RegisterReadObject(
m_stdio_communication.GetConnection()->GetReadObject(),
[this] (MainLoopBase &) { SendProcessOutput(); }, error);
if (! m_stdio_handle_up)
{
m_stdio_communication.Disconnect();
return error;
}
}
if ( m_process_launch_info.GetFileActionForFD(STDOUT_FILENO) &&
m_process_launch_info.GetFileActionForFD(STDERR_FILENO))
return;
return Error();
Error error;
lldbassert(! m_stdio_handle_up);
m_stdio_handle_up = m_mainloop.RegisterReadObject(
m_stdio_communication.GetConnection()->GetReadObject(),
[this] (MainLoopBase &) { SendProcessOutput(); }, error);
if (! m_stdio_handle_up)
{
// Not much we can do about the failure. Log it and continue without forwarding.
if (Log *log = GetLogIfAnyCategoriesSet(LIBLLDB_LOG_PROCESS))
log->Printf("GDBRemoteCommunicationServerLLGS::%s Failed to set up stdio forwarding: %s",
__FUNCTION__, error.AsCString());
}
}
void
GDBRemoteCommunicationServerLLGS::StopSTDIOForwarding()
{
Mutex::Locker locker(m_stdio_communication_mutex);
m_stdio_handle_up.reset();
}
@ -1020,7 +1038,6 @@ GDBRemoteCommunicationServerLLGS::SendProcessOutput()
char buffer[1024];
ConnectionStatus status;
Error error;
Mutex::Locker locker(m_stdio_communication_mutex);
while (true)
{
size_t bytes_read = m_stdio_communication.Read(buffer, sizeof buffer, 0, status, &error);
@ -1931,7 +1948,6 @@ GDBRemoteCommunicationServerLLGS::Handle_I (StringExtractorGDBRemote &packet)
// TODO: enqueue this block in circular buffer and send window size to remote host
ConnectionStatus status;
Error error;
Mutex::Locker locker(m_stdio_communication_mutex);
m_stdio_communication.Write(tmp, read, status, &error);
if (error.Fail())
{
@ -2835,7 +2851,6 @@ GDBRemoteCommunicationServerLLGS::MaybeCloseInferiorTerminalConnection ()
{
Log *log (GetLogIfAnyCategoriesSet(LIBLLDB_LOG_PROCESS));
Mutex::Locker locker(m_stdio_communication_mutex);
// Tell the stdio connection to shut down.
if (m_stdio_communication.IsConnected())
{

4
lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h
View File

@ -122,7 +122,6 @@ protected:
Mutex m_debugged_process_mutex;
NativeProcessProtocolSP m_debugged_process_sp;
Mutex m_stdio_communication_mutex; // Protects m_stdio_communication and m_stdio_handle_up
Communication m_stdio_communication;
MainLoop::ReadHandleUP m_stdio_handle_up;
@ -297,6 +296,9 @@ private:
void
SendProcessOutput ();
void
StartSTDIOForwarding();
void
StopSTDIOForwarding();