Did you also fix the pthread_mutex_unlock when it was already unlocked?  The cmake patch should get included too. For me this dumps core with an abort, so it sounds like the thread thing: Using device 0: ezcap USB 2.0 DVB-T/DAB/FM dongle Found Rafael Micro R820T tuner Oversampling input by: 2x. Oversampling output by: 4x. Buffer size: 6.02ms Tuned to 88856000 Hz. Sampling at 1360000 Hz. Output at 32000 Hz. Exact sample rate is: 1360000.050439 Hz Tuner gain set to automatic. Reading samples in sync mode... In:0.00% 00:00:00.00 [00:00:00.00] Out:0     [      |      ]        Clip:0 Done. Abort (core dumped) This is OpenBSD 5.2 with the libusbs from ports: d530# pkg_info | grep libusb libusb-compat-0.1.4 libusb-0.1 compatibility layer for libusb1 libusb1-1.0.9p3     library for USB device access from userspace   Alan ----- Radio Astronomy - the ultimate DX --- On Tue, 4/23/13, Stuart Henderson &lt;stu(a)spacehopper.org&gt; wrote: From: Stuart Henderson &lt;stu(a)spacehopper.org&gt; Subject: [PATCH 1/1] add -S (synchronous) mode to rtl_fm To: osmocom-sdr(a)lists.osmocom.org Date: Tuesday, April 23, 2013, 10:47 AM The enclosed diff adds a synchronous mode to rtl_fm. This helps OpenBSD (where libusb async isn't yet working). Signed-off-by: Stuart Henderson &lt;stu(a)spacehopper.org&gt; --- src/rtl_fm.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) diff --git a/src/rtl_fm.c b/src/rtl_fm.c index e8ebb77..a71e287 100644 --- a/src/rtl_fm.c +++ b/src/rtl_fm.c @@ -128,6 +128,7 @@ void usage(void)         "\t[-E sets lower edge tuning (default: center)]\n"         "\t[-N enables NBFM mode (default: on)]\n"         "\t[-W enables WBFM mode (default: off)]\n" +        "\t[-S force sync output (default: async)]\n"         "\t (-N -s 170k -o 4 -A fast -r 32k -l 0 -D)\n"         "\tfilename (a '-' dumps samples to stdout)\n"         "\t (omitting the filename also uses stdout)\n\n" @@ -723,12 +724,14 @@ int main(int argc, char **argv)     uint32_t dev_index = 0;     int device_count;     int ppm_error = 0; +    int sync_mode = 0;     char vendor[256], product[256], serial[256]; +     fm_init(&fm);     pthread_mutex_init(&data_ready, NULL);     pthread_mutex_init(&data_write, NULL); -    while ((opt = getopt(argc, argv, "d:f:g:s:b:l:o:t:r:p:EFA:NWMULRDC")) != -1) { +    while ((opt = getopt(argc, argv, "d:f:g:s:b:l:o:t:r:p:EFA:NWMULRDSC")) != -1) {         switch (opt) {         case 'd':             dev_index = atoi(optarg); @@ -815,6 +818,9 @@ int main(int argc, char **argv)         case 'R':             fm.mode_demod = &raw_demod;             break; +        case 'S': +            sync_mode = 1; +            break;         default:             usage();             break; @@ -921,9 +927,24 @@ int main(int argc, char **argv)         fprintf(stderr, "WARNING: Failed to reset buffers.\n");}     pthread_create(&demod_thread, NULL, demod_thread_fn, (void *)(&fm)); -    rtlsdr_read_async(dev, rtlsdr_callback, (void *)(&fm), -                  DEFAULT_ASYNC_BUF_NUMBER, -                  lcm_post[fm.post_downsample] * DEFAULT_BUF_LENGTH); +    if (sync_mode) { +        fprintf(stderr, "Reading samples in sync mode...\n"); +        while (!do_exit) { +            r = rtlsdr_read_sync(dev, &fm.buf, +                         lcm_post[fm.post_downsample] * DEFAULT_BUF_LENGTH, +                         &fm.buf_len); +            if (r < 0) { +                fprintf(stderr, "WARNING: sync read failed.\n"); +                break; +            } +            full_demod(&fm); +        } +    } else { +        fprintf(stderr, "Reading samples in async mode...\n"); +        rtlsdr_read_async(dev, rtlsdr_callback, (void *)(&fm), +                  DEFAULT_ASYNC_BUF_NUMBER, +                  lcm_post[fm.post_downsample] * DEFAULT_BUF_LENGTH); +    }     if (do_exit) {         fprintf(stderr, "\nUser cancel, exiting...\n");} -- 1.8.1.3