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-rw-r--r--src/rtl_adsb.c26
1 files changed, 16 insertions, 10 deletions
diff --git a/src/rtl_adsb.c b/src/rtl_adsb.c
index 10447cd..bb0c8d2 100644
--- a/src/rtl_adsb.c
+++ b/src/rtl_adsb.c
@@ -59,7 +59,8 @@
#define BADSAMPLE 255
static pthread_t demod_thread;
-static pthread_mutex_t data_ready; /* locked when no data available */
+static pthread_cond_t ready;
+static pthread_mutex_t ready_m;
static volatile int do_exit = 0;
static rtlsdr_dev_t *dev = NULL;
@@ -77,6 +78,10 @@ int adsb_frame[14];
#define long_frame 112
#define short_frame 56
+/* signals are not threadsafe by default */
+#define safe_cond_signal(n, m) pthread_mutex_lock(m); pthread_cond_signal(n); pthread_mutex_unlock(m)
+#define safe_cond_wait(n, m) pthread_mutex_lock(m); pthread_cond_wait(n, m); pthread_mutex_unlock(m)
+
void usage(void)
{
fprintf(stderr,
@@ -145,11 +150,11 @@ void display(int *frame, int len)
}
int abs8(int x)
-/* do not subtract 128 from the raw iq, this handles it */
+/* do not subtract 127 from the raw iq, this handles it */
{
- if (x >= 128) {
- return x - 128;}
- return 128 - x;
+ if (x >= 127) {
+ return x - 127;}
+ return 127 - x;
}
void squares_precompute(void)
@@ -338,15 +343,14 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
if (do_exit) {
return;}
memcpy(buffer, buf, len);
- pthread_mutex_trylock(&data_ready);
- pthread_mutex_unlock(&data_ready);
+ safe_cond_signal(&ready, &ready_m);
}
static void *demod_thread_fn(void *arg)
{
int len;
while (!do_exit) {
- pthread_mutex_lock(&data_ready);
+ safe_cond_wait(&ready, &ready_m);
len = magnitute(buffer, DEFAULT_BUF_LENGTH);
manchester((uint16_t*)buffer, len);
messages((uint16_t*)buffer, len);
@@ -366,7 +370,8 @@ int main(int argc, char **argv)
int dev_index = 0;
int dev_given = 0;
int ppm_error = 0;
- pthread_mutex_init(&data_ready, NULL);
+ pthread_cond_init(&ready, NULL);
+ pthread_mutex_init(&ready_m, NULL);
squares_precompute();
while ((opt = getopt(argc, argv, "d:g:p:e:Q:VS")) != -1)
@@ -477,7 +482,8 @@ int main(int argc, char **argv)
else {
fprintf(stderr, "\nLibrary error %d, exiting...\n", r);}
rtlsdr_cancel_async(dev);
- pthread_mutex_destroy(&data_ready);
+ pthread_cond_destroy(&ready);
+ pthread_mutex_destroy(&ready_m);
if (file != stdout) {
fclose(file);}