kernel: reimplement k_uptime_get_32()
The current implementation does not return the low 32 bits of
k_uptime_get() as suggested by it's documentation; it returns the number
of milliseconds represented by the low 32-bits of the underlying system
clock. The truncation before translation results in discontinuities at
every point where the system clock increments bit 33.
Reimplement it using the full-precision value, and update the
documentation to note that this variant has little value for
long-running applications.
Closes #18739.
Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
diff --git a/include/kernel.h b/include/kernel.h
index 3c83c10..e36f059 100644
--- a/include/kernel.h
+++ b/include/kernel.h
@@ -1729,13 +1729,14 @@
/**
* @brief Get system uptime (32-bit version).
*
- * This routine returns the lower 32-bits of the elapsed time since the system
- * booted, in milliseconds.
+ * This routine returns the lower 32 bits of the system uptime in
+ * milliseconds.
*
- * This routine can be more efficient than k_uptime_get(), as it reduces the
- * need for interrupt locking and 64-bit math. However, the 32-bit result
- * cannot hold a system uptime time larger than approximately 50 days, so the
- * caller must handle possible rollovers.
+ * Because correct conversion requires full precision of the system
+ * clock there is no benefit to using this over k_uptime_get() unless
+ * you know the application will never run long enough for the system
+ * clock to approach 2^32 ticks. Calls to this function may involve
+ * interrupt blocking and 64-bit math.
*
* @note
* @rst
@@ -1744,9 +1745,12 @@
* :option:`CONFIG_SYS_CLOCK_TICKS_PER_SEC` config option
* @endrst
*
- * @return Current uptime in milliseconds.
+ * @return The low 32 bits of the current uptime, in milliseconds.
*/
-__syscall u32_t k_uptime_get_32(void);
+static inline u32_t k_uptime_get_32(void)
+{
+ return (u32_t)k_uptime_get();
+}
/**
* @brief Get elapsed time.
diff --git a/kernel/timeout.c b/kernel/timeout.c
index 99f3d24..feed788 100644
--- a/kernel/timeout.c
+++ b/kernel/timeout.c
@@ -229,18 +229,6 @@
#endif
}
-u32_t z_impl_k_uptime_get_32(void)
-{
- return __ticks_to_ms(z_tick_get_32());
-}
-
-#ifdef CONFIG_USERSPACE
-Z_SYSCALL_HANDLER(k_uptime_get_32)
-{
- return z_impl_k_uptime_get_32();
-}
-#endif
-
s64_t z_impl_k_uptime_get(void)
{
return __ticks_to_ms(z_tick_get());
