diff --git a/dump1090.c b/dump1090.c
index c2d89f2..dfbabf1 100644
--- a/dump1090.c
+++ b/dump1090.c
@@ -382,6 +382,9 @@ static void backgroundTasks(void) {
         interactiveShowData();
     }
 
+    // copy out reader CPU time and reset it
+    sdrUpdateCPUTime(&Modes.stats_current.reader_cpu);
+
     // always update end time so it is current when requests arrive
     Modes.stats_current.end = mstime();
 
@@ -703,11 +706,6 @@ int main(int argc, char **argv) {
 
             // Modes.data_mutex is locked, and possibly we have data.
 
-            // copy out reader CPU time and reset it
-            add_timespecs(&Modes.reader_cpu_accumulator, &Modes.stats_current.reader_cpu, &Modes.stats_current.reader_cpu);
-            Modes.reader_cpu_accumulator.tv_sec = 0;
-            Modes.reader_cpu_accumulator.tv_nsec = 0;
-
             if (Modes.first_free_buffer != Modes.first_filled_buffer) {
                 // FIFO is not empty, process one buffer.
 
diff --git a/dump1090.h b/dump1090.h
index f45bb34..3f0c8d3 100644
--- a/dump1090.h
+++ b/dump1090.h
@@ -301,7 +301,9 @@ struct _Modes {                             // Internal state
     struct mag_buf  mag_buffers[MODES_MAG_BUFFERS];       // Converted magnitude buffers from RTL or file input
     unsigned        first_free_buffer;                    // Entry in mag_buffers that will next be filled with input.
     unsigned        first_filled_buffer;                  // Entry in mag_buffers that has valid data and will be demodulated next. If equal to next_free_buffer, there is no unprocessed data.
-    struct timespec reader_cpu_accumulator;               // CPU time used by the reader thread, copied out and reset by the main thread under the mutex
+    pthread_mutex_t reader_cpu_mutex;                     // mutex protecting reader_cpu_accumulator
+    struct timespec reader_cpu_accumulator;               // accumulated CPU time used by the reader thread
+    struct timespec reader_cpu_start;                     // start time for the last reader thread CPU measurement
 
     unsigned        trailing_samples;                     // extra trailing samples in magnitude buffers
     double          sample_rate;                          // actual sample rate in use (in hz)
diff --git a/sdr.c b/sdr.c
index 1f76997..1b578d3 100644
--- a/sdr.c
+++ b/sdr.c
@@ -168,16 +168,45 @@ static sdr_handler *current_handler()
 
 bool sdrOpen()
 {
+    pthread_mutex_init(&Modes.reader_cpu_mutex, NULL);
     return current_handler()->open();
 }
 
 void sdrRun()
 {
     set_thread_name("dump1090-sdr");
+
+    pthread_mutex_lock(&Modes.reader_cpu_mutex);
+    Modes.reader_cpu_accumulator.tv_sec = 0;
+    Modes.reader_cpu_accumulator.tv_nsec = 0;
+    start_cpu_timing(&Modes.reader_cpu_start);
+    pthread_mutex_unlock(&Modes.reader_cpu_mutex);
+
     current_handler()->run();
+
+    pthread_mutex_lock(&Modes.reader_cpu_mutex);
+    end_cpu_timing(&Modes.reader_cpu_start, &Modes.reader_cpu_accumulator);
+    pthread_mutex_unlock(&Modes.reader_cpu_mutex);
 }
 
 void sdrClose()
 {
+    pthread_mutex_destroy(&Modes.reader_cpu_mutex);
     current_handler()->close();
 }
+
+void sdrMonitor()
+{
+    pthread_mutex_lock(&Modes.reader_cpu_mutex);
+    update_cpu_timing(&Modes.reader_cpu_start, &Modes.reader_cpu_accumulator);
+    pthread_mutex_unlock(&Modes.reader_cpu_mutex);
+}
+
+void sdrUpdateCPUTime(struct timespec *addTo)
+{
+    pthread_mutex_lock(&Modes.reader_cpu_mutex);
+    add_timespecs(&Modes.reader_cpu_accumulator, addTo, addTo);
+    Modes.reader_cpu_accumulator.tv_sec = 0;
+    Modes.reader_cpu_accumulator.tv_nsec = 0;
+    pthread_mutex_unlock(&Modes.reader_cpu_mutex);
+}
diff --git a/sdr.h b/sdr.h
index 4bd20a6..ba030e7 100644
--- a/sdr.h
+++ b/sdr.h
@@ -30,4 +30,9 @@ bool sdrOpen();
 void sdrRun();
 void sdrClose();
 
+// Call periodically from the SDR read thread to update reader thread CPU stats:
+void sdrMonitor();
+// Retrieve CPU stats and add new CPU time to *addTo
+void sdrUpdateCPUTime(struct timespec *addTo);
+
 #endif
diff --git a/sdr_bladerf.c b/sdr_bladerf.c
index 69fe799..673183f 100644
--- a/sdr_bladerf.c
+++ b/sdr_bladerf.c
@@ -300,7 +300,6 @@ bool bladeRFOpen()
     return false;
 }
 
-static struct timespec thread_cpu;
 static unsigned timeouts = 0;
 
 static void *handle_bladerf_samples(struct bladerf *dev,
@@ -322,6 +321,8 @@ static void *handle_bladerf_samples(struct bladerf *dev,
     // record initial time for later sys timestamp calculation
     uint64_t entryTimestamp = mstime();
 
+    sdrMonitor();
+
     pthread_mutex_lock(&Modes.data_mutex);
     if (Modes.exit) {
         pthread_mutex_unlock(&Modes.data_mutex);
@@ -430,10 +431,6 @@ static void *handle_bladerf_samples(struct bladerf *dev,
         // Push the new data to the demodulation thread
         pthread_mutex_lock(&Modes.data_mutex);
 
-        // accumulate CPU while holding the mutex, and restart measurement
-        end_cpu_timing(&thread_cpu, &Modes.reader_cpu_accumulator);
-        start_cpu_timing(&thread_cpu);
-
         Modes.mag_buffers[next_free_buffer].dropped = 0;
         Modes.mag_buffers[next_free_buffer].length = 0;  // just in case
         Modes.first_free_buffer = next_free_buffer;
@@ -482,8 +479,6 @@ void bladeRFRun()
         goto out;
     }
 
-    start_cpu_timing(&thread_cpu);
-
     timeouts = 0; // reset to zero when we get a callback with some data
  retry:
     if ((status = bladerf_stream(stream, BLADERF_MODULE_RX)) < 0) {
diff --git a/sdr_hackrf.c b/sdr_hackrf.c
index a3cd7cd..671c69a 100644
--- a/sdr_hackrf.c
+++ b/sdr_hackrf.c
@@ -195,8 +195,6 @@ bool hackRFOpen()
     return true;
 }
 
-struct timespec thread_cpu;
-
 static int handle_hackrf_samples(hackrf_transfer *transfer)
 {
     struct mag_buf *outbuf;
@@ -211,6 +209,8 @@ static int handle_hackrf_samples(hackrf_transfer *transfer)
     static int dropping = 0;
     static uint64_t sampleCounter = 0;
 
+    sdrMonitor();
+
     // Lock the data buffer variables before accessing them
     pthread_mutex_lock(&Modes.data_mutex);
     if (Modes.exit) {
@@ -271,10 +271,6 @@ static int handle_hackrf_samples(hackrf_transfer *transfer)
     Modes.mag_buffers[next_free_buffer].length = 0;  // just in case
     Modes.first_free_buffer = next_free_buffer;
 
-    // accumulate CPU while holding the mutex, and restart measurement
-    end_cpu_timing(&thread_cpu, &Modes.reader_cpu_accumulator);
-    start_cpu_timing(&thread_cpu);
-
     pthread_cond_signal(&Modes.data_cond);
     pthread_mutex_unlock(&Modes.data_mutex);
 
@@ -289,8 +285,6 @@ void hackRFRun()
         return;
     }
 
-    start_cpu_timing(&thread_cpu);
-
     int status = hackrf_start_rx(HackRF.device, &handle_hackrf_samples, NULL);
 
     if (status != 0) { 
diff --git a/sdr_ifile.c b/sdr_ifile.c
index f615071..d7ee0fc 100644
--- a/sdr_ifile.c
+++ b/sdr_ifile.c
@@ -179,9 +179,6 @@ void ifileRun()
     int eof = 0;
     struct timespec next_buffer_delivery;
 
-    struct timespec thread_cpu;
-    start_cpu_timing(&thread_cpu);
-
     uint64_t sampleCounter = 0;
 
     clock_gettime(CLOCK_MONOTONIC, &next_buffer_delivery);
@@ -205,6 +202,8 @@ void ifileRun()
         lastbuf = &Modes.mag_buffers[(Modes.first_free_buffer + MODES_MAG_BUFFERS - 1) % MODES_MAG_BUFFERS];
         pthread_mutex_unlock(&Modes.data_mutex);
 
+        sdrMonitor();
+
         // Compute the sample timestamp for the start of the block
         outbuf->sampleTimestamp = sampleCounter * 12e6 / Modes.sample_rate;
         sampleCounter += MODES_MAG_BUF_SAMPLES;
@@ -253,9 +252,6 @@ void ifileRun()
         // Push the new data to the main thread
         pthread_mutex_lock(&Modes.data_mutex);
         Modes.first_free_buffer = next_free_buffer;
-        // accumulate CPU while holding the mutex, and restart measurement
-        end_cpu_timing(&thread_cpu, &Modes.reader_cpu_accumulator);
-        start_cpu_timing(&thread_cpu);
         pthread_cond_signal(&Modes.data_cond);
     }
 
diff --git a/sdr_limesdr.c b/sdr_limesdr.c
index 920d341..13b1b03 100644
--- a/sdr_limesdr.c
+++ b/sdr_limesdr.c
@@ -315,8 +315,6 @@ bool limesdrOpen(void)
     return false;
 }
 
-static struct timespec limesdr_thread_cpu;
-
 static void limesdrCallback(unsigned char *buf, uint32_t len, void *ctx)
 {
     struct mag_buf *outbuf;
@@ -331,6 +329,8 @@ static void limesdrCallback(unsigned char *buf, uint32_t len, void *ctx)
 
     MODES_NOTUSED(ctx);
 
+    sdrMonitor();
+
     // Lock the data buffer variables before accessing them
     pthread_mutex_lock(&Modes.data_mutex);
     if (Modes.exit) {
@@ -396,10 +396,6 @@ static void limesdrCallback(unsigned char *buf, uint32_t len, void *ctx)
     Modes.mag_buffers[next_free_buffer].length = 0;  // just in case
     Modes.first_free_buffer = next_free_buffer;
 
-    // accumulate CPU while holding the mutex, and restart measurement
-    end_cpu_timing(&limesdr_thread_cpu, &Modes.reader_cpu_accumulator);
-    start_cpu_timing(&limesdr_thread_cpu);
-
     pthread_cond_signal(&Modes.data_cond);
     pthread_mutex_unlock(&Modes.data_mutex);
 }
@@ -414,8 +410,6 @@ void limesdrRun()
 
     LMS_StartStream(&LimeSDR.stream);
 
-    start_cpu_timing(&limesdr_thread_cpu);
-
     while (!LimeSDR.is_stop) {
         int sampleCnt = LMS_RecvStream(&LimeSDR.stream, buffer, MODES_RTL_BUF_SIZE / LimeSDR.bytes_in_sample, NULL, 1000);
         if (sampleCnt) {
diff --git a/sdr_rtlsdr.c b/sdr_rtlsdr.c
index b0299ce..7050eff 100644
--- a/sdr_rtlsdr.c
+++ b/sdr_rtlsdr.c
@@ -265,8 +265,6 @@ bool rtlsdrOpen(void) {
     return true;
 }
 
-static struct timespec rtlsdr_thread_cpu;
-
 static void rtlsdrCallback(unsigned char *buf, uint32_t len, void *ctx) {
     struct mag_buf *outbuf;
     struct mag_buf *lastbuf;
@@ -280,6 +278,8 @@ static void rtlsdrCallback(unsigned char *buf, uint32_t len, void *ctx) {
 
     MODES_NOTUSED(ctx);
 
+    sdrMonitor();
+
     // Lock the data buffer variables before accessing them
     pthread_mutex_lock(&Modes.data_mutex);
     if (Modes.exit) {
@@ -346,10 +346,6 @@ static void rtlsdrCallback(unsigned char *buf, uint32_t len, void *ctx) {
     Modes.mag_buffers[next_free_buffer].length = 0;  // just in case
     Modes.first_free_buffer = next_free_buffer;
 
-    // accumulate CPU while holding the mutex, and restart measurement
-    end_cpu_timing(&rtlsdr_thread_cpu, &Modes.reader_cpu_accumulator);
-    start_cpu_timing(&rtlsdr_thread_cpu);
-
     pthread_cond_signal(&Modes.data_cond);
     pthread_mutex_unlock(&Modes.data_mutex);
 }
@@ -360,8 +356,6 @@ void rtlsdrRun()
         return;
     }
 
-    start_cpu_timing(&rtlsdr_thread_cpu);
-
     rtlsdr_read_async(RTLSDR.dev, rtlsdrCallback, NULL,
                       /* MODES_RTL_BUFFERS */ 4,
                       MODES_RTL_BUF_SIZE);
diff --git a/util.c b/util.c
index f5baa18..bdaa38f 100644
--- a/util.c
+++ b/util.c
@@ -106,6 +106,17 @@ void end_cpu_timing(const struct timespec *start_time, struct timespec *add_to)
     normalize_timespec(add_to);
 }
 
+/* add difference between start_time and the current CPU time to add_to; then store the current CPU time in start_time */
+void update_cpu_timing(struct timespec *start_time, struct timespec *add_to)
+{
+    struct timespec end_time;
+    clock_gettime(CLOCK_THREAD_CPUTIME_ID, &end_time);
+    add_to->tv_sec += end_time.tv_sec - start_time->tv_sec;
+    add_to->tv_nsec += end_time.tv_nsec - start_time->tv_nsec;
+    normalize_timespec(add_to);
+    *start_time = end_time;
+}
+
 void set_thread_name(const char *name)
 {
 #if (__GLIBC__ > 2) || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 12)
diff --git a/util.h b/util.h
index af4185e..be2fe35 100644
--- a/util.h
+++ b/util.h
@@ -51,6 +51,9 @@ void start_cpu_timing(struct timespec *start_time);
 /* add difference between start_time and the current CPU time to add_to */
 void end_cpu_timing(const struct timespec *start_time, struct timespec *add_to);
 
+/* like end_cpu_timing followed by start_cpu_timing, but without a gap */
+void update_cpu_timing(struct timespec *start_time, struct timespec *add_to);
+
 /* set current thread name, if supported */
 void set_thread_name(const char *name);