Fix issues with inferior stdout coming out of order
Summary:
We've had a bug where two pieces of code, executing on two threads were
attempting to write inferior output simultaneously. The first one was in
Debugger::HandleProcessEvent, which handled the cases where stdout was
coming while the process was running. The second was in
CommandInterpreter::IOHandlerInputComplete, which was ensuring that any
output is printed before the command which caused process to run
terminates.
Both of these things make sense, but the fact they were implemented as
two independent functions without any synchronization meant that race
conditions could occur (e.g. both threads call process->GetSTDOUT, get
two chunks of data, but then end up calling stream->Write in opposite
order). This was most apparent in situations where a process quickly
writes a bunch of output and then exits (as all our register tests do).
This patch adds a mutex to ensure that stdout forwarding happens
atomically. It also refactors a code somewhat in order to reduce code
duplication.
Reviewers: clayborg, jingham
Subscribers: jfb, mgorny, lldb-commits
Differential Revision: https://reviews.llvm.org/D65152
llvm-svn: 367418
diff --git a/lldb/source/Interpreter/CommandInterpreter.cpp b/lldb/source/Interpreter/CommandInterpreter.cpp
index bd09f89..8af8cc42 100644
--- a/lldb/source/Interpreter/CommandInterpreter.cpp
+++ b/lldb/source/Interpreter/CommandInterpreter.cpp
@@ -2664,32 +2664,14 @@
}
}
-size_t CommandInterpreter::GetProcessOutput() {
- // The process has stuff waiting for stderr; get it and write it out to the
- // appropriate place.
- char stdio_buffer[1024];
- size_t len;
- size_t total_bytes = 0;
- Status error;
+void CommandInterpreter::GetProcessOutput() {
TargetSP target_sp(m_debugger.GetTargetList().GetSelectedTarget());
- if (target_sp) {
- ProcessSP process_sp(target_sp->GetProcessSP());
- if (process_sp) {
- while ((len = process_sp->GetSTDOUT(stdio_buffer, sizeof(stdio_buffer),
- error)) > 0) {
- size_t bytes_written = len;
- m_debugger.GetOutputFile()->Write(stdio_buffer, bytes_written);
- total_bytes += len;
- }
- while ((len = process_sp->GetSTDERR(stdio_buffer, sizeof(stdio_buffer),
- error)) > 0) {
- size_t bytes_written = len;
- m_debugger.GetErrorFile()->Write(stdio_buffer, bytes_written);
- total_bytes += len;
- }
- }
- }
- return total_bytes;
+ if (!target_sp)
+ return;
+
+ if (ProcessSP process_sp = target_sp->GetProcessSP())
+ m_debugger.FlushProcessOutput(*process_sp, /*flush_stdout*/ true,
+ /*flush_stderr*/ true);
}
void CommandInterpreter::StartHandlingCommand() {