sched/wdog: Faster wdog deleting.

This commit reduced 1 write operation for wdog deleting and decoupled
the WDOG_ISACTIVE with the list implementation.

Signed-off-by: ouyangxiangzhen <ouyangxiangzhen@xiaomi.com>

include/nuttx/list.h

@@ -138,20 +138,27 @@
     } \
   while (0)
 
-#define list_delete(item) \
+#define list_delete_fast(item) \
   do \
     { \
       FAR struct list_node *__item = (item); \
       __item->next->prev = __item->prev; \
       __item->prev->next = __item->next; \
-      __item->prev = __item->next = NULL; \
+    } \
+  while (0)
+
+#define list_delete(item) \
+  do \
+    { \
+      list_delete_fast(item); \
+      list_clear_node(item); \
     } \
   while (0)
 
 #define list_delete_init(item) \
   do \
     { \
-      list_delete(item); \
+      list_delete_fast(item); \
       list_initialize(item); \
     } \
   while (0)

include/nuttx/wdog.h

@@ -39,7 +39,7 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#define WDOG_ISACTIVE(w)   (list_in_list(&((w)->node)))
+#define WDOG_ISACTIVE(w)   ((w)->func != NULL)
 
 /* The maximum delay tick are supposed to be CLOCK_MAX >> 1.
  * However, if there are expired wdog timers in the wdog queue,

sched/wdog/wd_cancel.c

@@ -84,7 +84,11 @@ int wd_cancel(FAR struct wdog_s *wdog)
 
   /* Now, remove the watchdog from the timer queue */
 
-  list_delete(&wdog->node);
+  list_delete_fast(&wdog->node);
+
+  /* Mark the watchdog inactive */
+
+  wdog->func = NULL;
 
   spin_unlock_irqrestore(&g_wdspinlock, flags);
 

sched/wdog/wd_start.c

@@ -140,12 +140,13 @@ static inline_function void wd_expiration(clock_t ticks)
 
       /* Remove the watchdog from the head of the list */
 
-      list_delete(&wdog->node);
+      list_delete_fast(&wdog->node);
 
       /* Indicate that the watchdog is no longer active. */
 
       func = wdog->func;
       arg  = wdog->arg;
+      wdog->func = NULL;
 
       /* Execute the watchdog function */
 
@@ -286,7 +287,7 @@ int wd_start_abstick(FAR struct wdog_s *wdog, clock_t ticks,
   if (WDOG_ISACTIVE(wdog))
     {
       reassess |= list_is_head(&g_wdactivelist, &wdog->node);
-      list_delete(&wdog->node);
+      list_delete_fast(&wdog->node);
     }
 
   reassess |= wd_insert(wdog, ticks, wdentry, arg);
@@ -312,7 +313,7 @@ int wd_start_abstick(FAR struct wdog_s *wdog, clock_t ticks,
 
   if (WDOG_ISACTIVE(wdog))
     {
-      list_delete(&wdog->node);
+      list_delete_fast(&wdog->node);
     }
 
   wd_insert(wdog, ticks, wdentry, arg);