transceiver, uhd: dynamically allocate async event thread

Similar to the previous commit titled,

"multi-arfcn, trx: allocate threads on heap and fix thread release"

there is the potential for a segfault on exit if the event thread
is never started. As before, address the issue by initializing
the Thread pointer with NULL and later allocating the object
immediately prior to use.

On stop or exit, allow the thread to exit by checking a condition
variable. If device is stopped or never started, the same variable
can be checked for state, which avoids attempts to deallocate an
empty pointer.

If there is a better method to shutdown / deallocate using the
OpenBTS thread library, please let me know.

Signed-off-by: Thomas Tsou <ttsou@vt.edu>

1 files changed, 14 insertions, 5 deletions

diff --git a/Transceiver52M/UHDDevice.cpp b/Transceiver52M/UHDDevice.cpp
index 7b48cff..bd8e1c3 100644
--- a/Transceiver52M/UHDDevice.cpp
+++ b/Transceiver52M/UHDDevice.cpp
@@ -265,6 +265,7 @@ public:
 	    @return true if message received or false on timeout or error
 	*/
 	bool recv_async_msg();
+	bool running() { return started; }
 
 	enum err_code {
 		ERROR_TIMING = -1,
@@ -310,12 +311,12 @@ private:
 	std::string str_code(uhd::rx_metadata_t metadata);
 	std::string str_code(uhd::async_metadata_t metadata);
 
-	Thread async_event_thrd;
+	Thread *async_event_thrd;
 };
 
 void *async_event_loop(uhd_device *dev)
 {
-	while (1) {
+	while (dev->running()) {
 		dev->recv_async_msg();
 		pthread_testcancel();
 	}
@@ -349,6 +350,7 @@ uhd_device::uhd_device(int sps, bool skip_rx)
 	  tx_freq(0.0), rx_freq(0.0), tx_spp(0), rx_spp(0),
 	  started(false), aligned(false), rx_pkt_cnt(0), drop_cnt(0),
 	  prev_ts(0,0), ts_offset(0), rx_smpl_buf(NULL)
+	  async_event_thrd(NULL)
 {
 	this->sps = sps;
 	this->skip_rx = skip_rx;
@@ -677,10 +679,12 @@ bool uhd_device::start()
 		return false;
 	}
 
+	started = true;
 	setPriority();
 
 	// Start asynchronous event (underrun check) loop
-	async_event_thrd.start((void * (*)(void*))async_event_loop, (void*)this);
+	async_event_thrd = new Thread(32768);
+	async_event_thrd->start((void * (*)(void*))async_event_loop, (void*)this);
 
 	// Start streaming
 	restart(uhd::time_spec_t(0.0));
@@ -689,18 +693,23 @@ bool uhd_device::start()
 	double time_now = usrp_dev->get_time_now().get_real_secs();
 	LOG(INFO) << "The current time is " << time_now << " seconds";
 
-	started = true;
 	return true;
 }
 
 bool uhd_device::stop()
 {
+	if (!started)
+		return false;
+
+	started = false;
+
 	uhd::stream_cmd_t stream_cmd = 
 		uhd::stream_cmd_t::STREAM_MODE_STOP_CONTINUOUS;
 
 	usrp_dev->issue_stream_cmd(stream_cmd);
 
-	started = false;
+	delete async_event_thrd;
+
 	return true;
 }