Fixing a problem with thread creation signal order dependency
llvm-svn: 190831
diff --git a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
index 673ca180..3ce036b0 100644
--- a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
+++ b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
@@ -1595,6 +1595,80 @@
return ProcessMessage::Signal(pid, signo);
}
+// On Linux, when a new thread is created, we receive to notifications,
+// (1) a SIGTRAP|PTRACE_EVENT_CLONE from the main process thread with the
+// child thread id as additional information, and (2) a SIGSTOP|SI_USER from
+// the new child thread indicating that it has is stopped because we attached.
+// We have no guarantee of the order in which these arrive, but we need both
+// before we are ready to proceed. We currently keep a list of threads which
+// have sent the initial SIGSTOP|SI_USER event. Then when we receive the
+// SIGTRAP|PTRACE_EVENT_CLONE notification, if the initial stop has not occurred
+// we call ProcessMonitor::WaitForInitialTIDStop() to wait for it.
+
+bool
+ProcessMonitor::WaitForInitialTIDStop(lldb::tid_t tid)
+{
+ Log *log (ProcessPOSIXLog::GetLogIfAllCategoriesSet (POSIX_LOG_PROCESS));
+ if (log)
+ log->Printf ("ProcessMonitor::%s(%d) waiting for thread to stop...", __FUNCTION__, tid);
+
+ // Wait for the thread to stop
+ while (true)
+ {
+ int status = -1;
+ if (log)
+ log->Printf ("ProcessMonitor::%s(%d) waitpid...", __FUNCTION__, tid);
+ lldb::pid_t wait_pid = waitpid(tid, &status, __WALL);
+ if (status == -1)
+ {
+ // If we got interrupted by a signal (in our process, not the
+ // inferior) try again.
+ if (errno == EINTR)
+ continue;
+ else
+ {
+ if (log)
+ log->Printf("ProcessMonitor::%s(%d) waitpid error -- %s", __FUNCTION__, tid, strerror(errno));
+ return false; // This is bad, but there's nothing we can do.
+ }
+ }
+
+ if (log)
+ log->Printf ("ProcessMonitor::%s(%d) waitpid, status = %d", __FUNCTION__, tid, status);
+
+ assert(wait_pid == tid);
+
+ siginfo_t info;
+ int ptrace_err;
+ if (!GetSignalInfo(wait_pid, &info, ptrace_err))
+ {
+ if (log)
+ {
+ log->Printf ("ProcessMonitor::%s() GetSignalInfo failed. errno=%d (%s)", __FUNCTION__, ptrace_err, strerror(ptrace_err));
+ }
+ return false;
+ }
+
+ // If this is a thread exit, we won't get any more information.
+ if (WIFEXITED(status))
+ {
+ m_process->SendMessage(ProcessMessage::Exit(wait_pid, WEXITSTATUS(status)));
+ if (wait_pid == tid)
+ return true;
+ continue;
+ }
+
+ assert(info.si_code == SI_USER);
+ assert(WSTOPSIG(status) == SIGSTOP);
+
+ if (log)
+ log->Printf ("ProcessMonitor::%s(bp) received thread stop signal", __FUNCTION__);
+ m_process->AddThreadForInitialStopIfNeeded(wait_pid);
+ return true;
+ }
+ return false;
+}
+
bool
ProcessMonitor::StopThread(lldb::tid_t tid)
{