Author: gclayton
Date: Mon Jun 1 18:14:09 2015
New Revision: 238794
URL: http://llvm.org/viewvc/llvm-project?rev=238794&view=rev
Log:
Fix a race condition where 2 threads might try to call Process::SetExitStatus()
at the same time.
The problem was the mutex was only protecting the setting of m_exit_string and
m_exit_string, but this function relies on the m_private_state being set to
eStateExited in order to prevent more than 1 client setting the exit status. We
want to only allow the first caller to succeed.
On MacOSX we have a thread that reaps the process we are debugging, and we also
have a thread that monitors the debugserver process. When a process exists, the
ProcessGDBRemote::AsyncThread() would set the exit status to the correct value
and then another thread would reap the debugserver process and they would often
both end up in Process::SetExitStatus() at the same time. With the mutex at the
top we allow all variables to be set and the m_private_state to be set to
eStateExited _before_ the other thread (debugserver reaped) can try to set th
exist status to -1 and "lost connection to debugserver" being set as the exit
status.
This was probably an issue for lldb-server as well and could very well cleanup
some tests that might have been expecting a specific exit status from the
process being debugged.
Modified:
lldb/trunk/source/Target/Process.cpp
Modified: lldb/trunk/source/Target/Process.cpp
URL:
http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Target/Process.cpp?rev=238794&r1=238793&r2=238794&view=diff
==============================================================================
--- lldb/trunk/source/Target/Process.cpp (original)
+++ lldb/trunk/source/Target/Process.cpp Mon Jun 1 18:14:09 2015
@@ -1429,6 +1429,9 @@ Process::GetExitDescription ()
bool
Process::SetExitStatus (int status, const char *cstr)
{
+ // Use a mutex to protect setting the exit status.
+ Mutex::Locker locker (m_exit_status_mutex);
+
Log *log(lldb_private::GetLogIfAnyCategoriesSet (LIBLLDB_LOG_STATE |
LIBLLDB_LOG_PROCESS));
if (log)
log->Printf("Process::SetExitStatus (status=%i (0x%8.8x),
description=%s%s%s)",
@@ -1444,17 +1447,12 @@ Process::SetExitStatus (int status, cons
log->Printf("Process::SetExitStatus () ignoring exit status
because state was already set to eStateExited");
return false;
}
-
- // use a mutex to protect the status and string during updating
- {
- Mutex::Locker locker (m_exit_status_mutex);
- m_exit_status = status;
- if (cstr)
- m_exit_string = cstr;
- else
- m_exit_string.clear();
- }
+ m_exit_status = status;
+ if (cstr)
+ m_exit_string = cstr;
+ else
+ m_exit_string.clear();
// When we exit, we no longer need to the communication channel
m_stdio_communication.StopReadThread();
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