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PaulZC · PaulZC · commit 1aa3465014f9 · 2025-11-10T11:48:19.000Z
diff --git a/Firmware/RTK_Everywhere/RTK_Everywhere.ino b/Firmware/RTK_Everywhere/RTK_Everywhere.ino
@@ -895,6 +895,8 @@ typedef struct {
             updateSemaphore = xSemaphoreCreateMutex();
         if (xSemaphoreTake(updateSemaphore, 10 / portTICK_PERIOD_MS) == pdPASS)
         {
+            // The semaphore prevents the race condition where timer is updated after
+            // millis() is read but before the subtraction. It prevents retVal from underflowing
             retVal = millis() - timer;
             xSemaphoreGive(updateSemaphore);
         }

Original file line number	Diff line number	Diff line change
`@@ -895,6 +895,8 @@ typedef struct {`
`895`	`895`	`updateSemaphore = xSemaphoreCreateMutex();`
`896`	`896`	`if (xSemaphoreTake(updateSemaphore, 10 / portTICK_PERIOD_MS) == pdPASS)`
`897`	`897`	`{`
	`898`	`+ // The semaphore prevents the race condition where timer is updated after`
	`899`	`+ // millis() is read but before the subtraction. It prevents retVal from underflowing`
`898`	`900`	`retVal = millis() - timer;`
`899`	`901`	`xSemaphoreGive(updateSemaphore);`
`900`	`902`	`}`