Prevent timer underflow caused by very short wait periods

- Introduce minimum timer period (from Joe)
wallarug · Feb 1, 2020 · 7e459b8 · 7e459b8
1 parent a505046
commit 7e459b8
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Showing 2 changed files with 10 additions and 4 deletions.
diff --git a/inc/core/CodalConfig.h b/inc/core/CodalConfig.h
@@ -76,6 +76,15 @@ DEALINGS IN THE SOFTWARE.
 #define CODAL_TIMESTAMP                       uint32_t
 #endif
 
+//
+// Defines the default minimum period (in uS) a hardware timer can measure without
+// risk of a race condition. Can be overridden in a target config.json.
+//
+#ifndef CODAL_TIMER_MINIMUM_PERIOD
+#define CODAL_TIMER_MINIMUM_PERIOD            10
+#endif
+
+
 //
 // Fiber scheduler configuration
 //

diff --git a/source/driver-models/Timer.cpp b/source/driver-models/Timer.cpp
@@ -349,10 +349,7 @@ void Timer::trigger(bool isFallback)
     if (nextTimerEvent) {
         // this may possibly happen if a new timer event was added to the queue while
         // we were running - it might be already in the past
-        if (currentTimeUs < nextTimerEvent->timestamp)
-            triggerIn(nextTimerEvent->timestamp - currentTimeUs);
-        else
-            triggerIn(1);
+        triggerIn(max(nextTimerEvent->timestamp - currentTimeUs, CODAL_TIMER_MINIMUM_PERIOD));
     }
 }