3 files changed, 21 insertions, 4 deletions

diff --git a/firmware/export/timer.h b/firmware/export/timer.h
index b12ec55881..92b26db216 100644
--- a/firmware/export/timer.h
+++ b/firmware/export/timer.h
@@ -30,6 +30,7 @@
 #define TIMER_FREQ 1000000
 #endif
 
+/* NOTE: if unreg cb is defined you are in charge of calling timer_unregister() */
 bool timer_register(int reg_prio, void (*unregister_callback)(void),
                     long cycles, void (*timer_callback)(void)
                     IF_COP(,int core));
@@ -37,6 +38,10 @@ bool timer_set_period(long cycles);
 #ifdef CPU_COLDFIRE
 void timers_adjust_prescale(int multiplier, bool enable_irq);
 #endif
+
+/* NOTE: unregister callbacks are not called by timer_unregister()
+* the unregister_callback only gets called when your timer gets 
+* overwritten by a lower priority timer using timer_register() */
 void timer_unregister(void);
 
 /* target-specific interface */
diff --git a/firmware/target/hosted/kernel-unix.c b/firmware/target/hosted/kernel-unix.c
index e3c492a8cc..ed1f83cd8c 100644
--- a/firmware/target/hosted/kernel-unix.c
+++ b/firmware/target/hosted/kernel-unix.c
@@ -113,8 +113,8 @@ void (*global_timer_callback)(void);
 
 static void timer_cb(union sigval arg)
 {
-    (void)arg;
-    if (global_timer_callback)
+    /* check for spurious callbacks [arg.sival_ptr] */
+    if (global_timer_callback && global_timer_callback == arg.sival_ptr)
         global_timer_callback();
 }
 
@@ -129,12 +129,18 @@ bool timer_register(int reg_prio, void (*unregister_callback)(void),
     if (reg_prio <= timer_prio || in_us <= 0)
         return false;
 
-    if (timer_prio >= 0 && global_unreg_callback)
-        global_unreg_callback();
+    if(timer_prio >= 0)
+    {
+        if (global_unreg_callback) /* timer has callback user needs to unreg */
+            global_unreg_callback();
+        else /* no callback -- delete timer */
+            timer_delete(timer_tid);
+    }
 
     memset(&sigev, 0, sizeof(sigevent_t));
     sigev.sigev_notify = SIGEV_THREAD,
     sigev.sigev_notify_function = timer_cb;
+    sigev.sigev_value.sival_ptr = timer_callback; /* store cb to check later */
 
     div_t q = div(in_us, 1000000);
     ts.it_value.tv_sec = ts.it_interval.tv_sec = q.quot;
@@ -166,4 +172,6 @@ void timer_unregister(void)
 {
     timer_delete(timer_tid);
     timer_prio = -1;
+    global_unreg_callback = NULL;
+    global_timer_callback = NULL;
 }
diff --git a/firmware/timer.c b/firmware/timer.c
index a923290a94..c618f72e02 100644
--- a/firmware/timer.c
+++ b/firmware/timer.c
@@ -42,6 +42,7 @@ bool timer_register(int reg_prio, void (*unregister_callback)(void),
         return false;
 
     pfn_timer = timer_callback;
+    /* NOTE: if unreg cb is defined you are in charge of calling timer_unregister() */
     pfn_unregister = unregister_callback;
     timer_prio = reg_prio;
 
@@ -53,6 +54,9 @@ bool timer_set_period(long cycles)
     return timer_set(cycles, false);
 }
 
+/* NOTE: unregister callbacks are not called by timer_unregister()
+* the unregister_callback only gets called when your timer gets 
+* overwritten by a lower priority timer using timer_register() */
 void timer_unregister(void)
 {
     timer_stop();