Fix-Point commented on code in PR #17675:
URL: https://github.com/apache/nuttx/pull/17675#discussion_r2647022338
##########
include/nuttx/hrtimer.h:
##########
@@ -28,190 +28,182 @@
****************************************************************************/
#include <nuttx/config.h>
-#include <nuttx/clock.h>
-#include <nuttx/compiler.h>
-#include <nuttx/spinlock.h>
-#include <stdint.h>
-#include <sys/tree.h>
+#include <nuttx/hrtimer_queue_type.h>
/****************************************************************************
* Public Types
****************************************************************************/
-/* High-resolution timer modes
- *
- * HRTIMER_MODE_ABS - Absolute expiration time
- * HRTIMER_MODE_REL - Relative timeout from the current time
- */
-
-enum hrtimer_mode_e
-{
- HRTIMER_MODE_ABS = 0, /* Absolute expiration time */
- HRTIMER_MODE_REL /* Relative delay from now */
-};
-
-/* High-resolution timer states
- *
- * State transitions are managed internally by the hrtimer framework.
- * Callers must not modify the state directly.
- */
+#ifdef CONFIG_HRTIMER_LIST
+typedef struct hrtimer_list_s hrtimer_t;
+typedef struct hrtimer_list_queue_s hrtimer_queue_t;
+#else
+typedef struct hrtimer_rb_s hrtimer_t;
+typedef struct hrtimer_rb_queue_s hrtimer_queue_t;
+#endif
-enum hrtimer_state_e
+#ifdef __cplusplus
+#define EXTERN extern "C"
+extern "C"
{
- HRTIMER_STATE_INACTIVE = 0, /* Timer is inactive and not queued */
- HRTIMER_STATE_ARMED, /* Timer is armed and waiting for expiry */
- HRTIMER_STATE_RUNNING, /* Timer callback is currently executing */
- HRTIMER_STATE_CANCELED /* Timer canceled (callback may be running) */
-};
-
-/* Forward declarations */
+#else
+#define EXTERN extern
+#endif
-struct hrtimer_s;
-struct hrtimer_node_s;
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
-typedef struct hrtimer_s hrtimer_t;
-typedef struct hrtimer_node_s hrtimer_node_t;
+/* Wrapped version for NuttX scheduler. */
-/* Callback type for high-resolution timer expiration
+/****************************************************************************
+ * Name: hrtimer_async_restart
*
- * The callback is invoked when the timer expires. It is executed in
- * timer context and must not block.
- */
-
-typedef uint32_t (*hrtimer_cb)(FAR struct hrtimer_s *hrtimer);
-
-/* Red-black tree node used to order hrtimers by expiration time */
-
-struct hrtimer_node_s
-{
- RB_ENTRY(hrtimer_node_s) entry; /* RB-tree linkage */
-};
-
-/* High-resolution timer object
+ * Description:
+ * Restart the hrtimer with relative or absolute time in nanoseconds.
+ * These functions allow restarting the hrtimer that has been set to
+ * cancelled state via `hrtimer_async_cancel`.
+ * Please be aware of concurrency issues. Concurrency errors are prone to
+ * occur in this use case.
+ *
+ * Input Parameters:
+ * timer - The hrtimer to be started.
+ *
+ * Returned Value:
+ * Zero on success.
+ * -EINVAL on if one of the parameter is invalid.
+ *
+ * Assumption:
+ * The timer and func should be not NULL.
+ * The timer should be cancelled or completed.
*
- * The timer is ordered by absolute expiration time and managed by the
- * hrtimer core. The content of this structure should not be accessed
- * directly by users except through the provided APIs.
- */
-
-struct hrtimer_s
-{
- hrtimer_node_t node; /* RB-tree node for sorted insertion */
- enum hrtimer_state_e state; /* Current timer state */
- hrtimer_cb func; /* Expiration callback function */
- FAR void *arg; /* Argument passed to callback */
- uint64_t expired; /* Absolute expiration time (ns) */
-};
-
-/****************************************************************************
- * Public Function Prototypes
****************************************************************************/
-#ifdef __cplusplus
-#define EXTERN extern "C"
-extern "C"
-{
-#else
-#define EXTERN extern
-#endif
+int hrtimer_async_restart(FAR hrtimer_t *timer);
/****************************************************************************
- * Name: hrtimer_init
+ * Name: hrtimer_start
*
* Description:
- * Initialize a high-resolution timer instance. This function sets the
- * expiration callback and its argument. The timer is initialized in the
- * inactive state and is not armed until hrtimer_start() is called.
+ * Start the hrtimer with relative or absolute time in nanoseconds.
+ * These functions can only be called when the caller has the ownership of
+ * the timer.
*
* Input Parameters:
- * hrtimer - Pointer to the hrtimer instance to be initialized
- * func - Expiration callback function
- * arg - Argument passed to the callback
+ * timer - The hrtimer to be started.
+ * func - The callback function to be called when the hrtimer expires.
+ * arg - The argument to be passed to the callback function.
+ * time - The relative or absolute expiration time in nanoseconds.
+ * mode - The timer mode, relative or absolute.
*
* Returned Value:
- * None
+ * Zero on success.
+ * -EINVAL on if one of the parameter is invalid or the timer is in pending
+ * state.
+ *
****************************************************************************/
static inline_function
-void hrtimer_init(FAR hrtimer_t *hrtimer,
- hrtimer_cb func,
- FAR void *arg)
+int hrtimer_restart(hrtimer_t *timer, hrtimer_callback_t func,
+ FAR void *arg, uint64_t time, uint32_t mode)
{
- hrtimer->state = HRTIMER_STATE_INACTIVE;
- hrtimer->func = func;
- hrtimer->arg = arg;
+ uint64_t expired = time;
+
+ if (mode == HRTIMER_MODE_REL)
+ {
+ expired = time <= HRTIMER_MAX_DELAY ? time : HRTIMER_MAX_DELAY;
+ expired += clock_systime_nsec();
+ }
+
+ DEBUGASSERT(mode <= 1u);
+
+ hrtimer_fill(timer, func, arg, expired);
+ return hrtimer_async_restart(timer);
+}
+
+static inline_function
+int hrtimer_start(FAR hrtimer_t *timer, hrtimer_callback_t func,
Review Comment:
Compared to previous implementation,
- when restarting the timer, writing the three fields—`func`, `arg`, and
`expired`—does **indeed involve two additional writes** compared to writing
only `expired`.
- However, within the critical section, this implementation does not require
modifying the `func` of the hrtimer, which **saves one write operation**
compared to the need to write the `state` field, resulting in an **overall
increase of one `write` outside the critical section**.
The advantage of this interface design is that it reuses `func` to encode
the state of the hrtimer, saving 4 bytes of space per `hrtimer`.
I believe the **slight overhead outside the critical section will be hidden
by the pipeline** and should not have a significant impact on overall
performance. I will attempt to write test cases to compare the performance of
the two implementations.
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