add watchDog to detect hanging rtl-sdr

Author: wiedehopf

acarsdec.c

@@ -44,6 +44,8 @@ int mdly=600;
 int hourly = 0;
 int daily = 0;
 
+int signalExit = 0;
+
 #ifdef WITH_RTL
 int gain = -100;
 int ppm = 0;
@@ -159,6 +161,7 @@ static void sigintHandler(int signum)
 	else
 		fprintf(stderr, "Received signal %d, exiting.\n", strsignal(signum));
 #ifdef WITH_RTL
+	signalExit = 1;
 	runRtlCancel();
 #else
 	exit(0);

acarsdec.h

@@ -130,6 +130,7 @@ extern unsigned long wrkmask;
 extern pthread_mutex_t datamtx;
 extern pthread_cond_t datawcd;
 
+extern int signalExit;
 
 extern int inpmode;
 extern int verbose;

rtl.c

@@ -26,6 +26,8 @@
 #include <math.h>
 #include <rtl-sdr.h>
 #include "acarsdec.h"
+#include <signal.h>
+#include <unistd.h>
 
 // set the sameple rate by changing RTMULT
 // 2.5Ms/s is the best but could be over limit for some hardware
@@ -39,6 +41,9 @@ static int status = 0;
 static int rtlInBufSize = 0;
 static int rtlInRate = 0;
 
+static int watchdogCounter = 50;
+static pthread_mutex_t cbMutex = PTHREAD_MUTEX_INITIALIZER;
+
 #define RTLOUTBUFSZ 1024
 
 
@@ -300,6 +305,10 @@ static void in_callback(unsigned char *rtlinbuff, uint32_t nread, void *ctx)
 {
 	int n;
 
+	pthread_mutex_lock(&cbMutex);
+	watchdogCounter = 50;
+	pthread_mutex_unlock(&cbMutex);
+
 	if (nread != rtlInBufSize) {
 		fprintf(stderr, "warning: partial read\n");
 		return;
@@ -334,9 +343,46 @@ static void in_callback(unsigned char *rtlinbuff, uint32_t nread, void *ctx)
 	}
 }
 
+static void *readThreadEntryPoint(void *arg) {
+	rtlsdr_read_async(dev, in_callback, NULL, 4, rtlInBufSize);
+	pthread_mutex_lock(&cbMutex);
+	signalExit = 1;
+	pthread_mutex_unlock(&cbMutex);
+	return NULL;
+}
+
 int runRtlSample(void)
 {
-	rtlsdr_read_async(dev, in_callback, NULL, 4, rtlInBufSize);
+	pthread_t readThread;
+	pthread_create(&readThread, NULL, readThreadEntryPoint, NULL);
+
+	pthread_mutex_lock(&cbMutex);
+
+	while (!signalExit) {
+		if (--watchdogCounter <= 0) {
+			fprintf(stderr, "No data from the SDR for 5 seconds, exiting ...\n");
+			runRtlCancel(); // watchdog triggered after 5 seconds of no data from SDR
+			break;
+		}
+		pthread_mutex_unlock(&cbMutex);
+		usleep(100 * 1000); // 0.1 seconds
+		pthread_mutex_lock(&cbMutex);
+	}
+
+	pthread_mutex_unlock(&cbMutex);
+
+	int count = 100; // 10 seconds
+	int err = 0;
+	// Wait on reader thread exit
+	while (count-- > 0 && (err = pthread_tryjoin_np(readThread, NULL))) {
+		usleep(100 * 1000); // 0.1 seconds
+	}
+	if (err) {
+		fprintf(stderr, "Receive thread termination failed, will raise SIGKILL to ensure we die!\n");
+		raise(SIGKILL);
+		return 1;
+	}
+
 	return 0;
 }