If there mutliple low-priority worker threads, only one needs to perform garbage collection

sched/wqueue/kwork_hpthread.c

@@ -108,22 +108,27 @@ static int work_hpthread(int argc, char *argv[])
 
   for (;;)
     {
-      /* First, perform garbage collection.  This cleans-up memory de-allocations
+#ifndef CONFIG_SCHED_LPWORK
-       * that were queued because they could not be freed in that execution
+      /* First, perform garbage collection.  This cleans-up memory
-       * context (for example, if the memory was freed from an interrupt handler).
+       * de-allocations that were queued because they could not be freed in
+       * that execution context (for example, if the memory was freed from
+       * an interrupt handler).
+       *
        * NOTE: If the work thread is disabled, this clean-up is performed by
-       * the IDLE thread (at a very, very low priority).
+       * the IDLE thread (at a very, very low priority).  If the low-priority
+       * work thread is enabled, then the garbage collection is done on that
+       * thread instead.
        */
 
-#ifndef CONFIG_SCHED_LPWORK
       sched_garbagecollection();
 #endif
 
-      /* Then process queued work.  We need to keep interrupts disabled while
+      /* Then process queued work.  work_process will not return until: (1)
-       * we process items in the work list.
+       * there is no further work in the work queue, and (2) the polling
+       * period provided by g_hpwork.delay expires.
        */
 
-      work_process((FAR struct kwork_wqueue_s *)&g_hpwork, 0);
+      work_process((FAR struct kwork_wqueue_s *)&g_hpwork, g_hpwork.delay, 0);
     }
 
   return OK; /* To keep some compilers happy */

sched/wqueue/kwork_lpthread.c

@@ -106,52 +106,65 @@ struct lp_wqueue_s g_lpwork;
 
 static int work_lpthread(int argc, char *argv[])
 {
+#if CONFIG_SCHED_LPNTHREADS > 0
   int wndx;
+  pid_t me = getpid();
+  int i;
 
   /* Find out thread index by search the workers in g_lpwork */
 
-  {
+  for (wndx = 0, i = 0; i < CONFIG_SCHED_LPNTHREADS; i++)
-    pid_t me = getpid();
+    {
-    int i;
+      if (g_lpwork.worker[i].pid == me)
+        {
+          wndx = i;
+          break;
+        }
+    }
 
-    /* Check each entry if we have to */
+  DEBUGASSERT(i < CONFIG_SCHED_LPNTHREADS);
-
+#endif
-    for (wndx = 0, i = 0; i < CONFIG_SCHED_LPNTHREADS; i++)
-      {
-        if (g_lpwork.worker[i].pid == me)
-          {
-            wndx = i;
-            break;
-          }
-      }
-
-    DEBUGASSERT(i < CONFIG_SCHED_LPNTHREADS);
-  }
 
   /* Loop forever */
 
   for (;;)
     {
-      /* First, perform garbage collection.  This cleans-up memory de-allocations
+#if CONFIG_SCHED_LPNTHREADS > 0
-       * that were queued because they could not be freed in that execution
+      /* Thread 0 is special.  Only thread 0 performs period garbage collection */
-       * context (for example, if the memory was freed from an interrupt handler).
-       * NOTE: If the work thread is disabled, this clean-up is performed by
-       * the IDLE thread (at a very, very low priority).
-       *
-       * In the event of multiple low priority threads, on index == 0 will do
-       * the garbage collection.
-       */
 
-      if (wndx == 0)
+      if (wndx > 0)
         {
-          sched_garbagecollection();
+          /* The other threads will perform work, waiting indefinitely until
+           * signalled for the next work availability.
+           *
+           * The special value of zero for the poll period instructs work_process
+           * to wait indefinitely until a signal is received.
+           */
+
+          work_process((FAR struct kwork_wqueue_s *)&g_lpwork, 0, wndx);
         }
+      else
+#endif
+        {
+          /* Perform garbage collection.  This cleans-up memory de-allocations
+          * that were queued because they could not be freed in that execution
+          * context (for example, if the memory was freed from an interrupt handler).
+          * NOTE: If the work thread is disabled, this clean-up is performed by
+          * the IDLE thread (at a very, very low priority).
+          *
+          * In the event of multiple low priority threads, on index == 0 will do
+          * the garbage collection.
+          */
 
-      /* Then process queued work.  We need to keep interrupts disabled while
+          sched_garbagecollection();
-       * we process items in the work list.
-       */
 
-      work_process((FAR struct kwork_wqueue_s *)&g_lpwork, wndx);
+          /* Then process queued work.  work_process will not return until:
+           * (1) there is no further work in the work queue, and (2) the polling
+           * period provided by g_lpwork.delay expires.
+           */
+
+          work_process((FAR struct kwork_wqueue_s *)&g_lpwork, g_lpwork.delay, 0);
+        }
     }
 
   return OK; /* To keep some compilers happy */

sched/wqueue/kwork_process.c

@@ -41,6 +41,7 @@
 
 #include <stdint.h>
 #include <unistd.h>
+#include <signal.h>
 #include <queue.h>
 
 #include <nuttx/clock.h>
@@ -107,7 +108,7 @@
  *
  ****************************************************************************/
 
-void work_process(FAR struct kwork_wqueue_s *wqueue, int wndx)
+void work_process(FAR struct kwork_wqueue_s *wqueue, uint32_t period, int wndx)
 {
   volatile FAR struct work_s *work;
   worker_t  worker;
@@ -123,7 +124,7 @@ void work_process(FAR struct kwork_wqueue_s *wqueue, int wndx)
    * we process items in the work list.
    */
 
-  next  = wqueue->delay;
+  next  = period;
   flags = irqsave();
 
   /* Get the time that we started this polling cycle in clock ticks. */
@@ -221,21 +222,41 @@ void work_process(FAR struct kwork_wqueue_s *wqueue, int wndx)
         }
     }
 
-  /* Get the delay (in clock ticks) since we started the sampling */
+#if defined(CONFIG_SCHED_LPWORK) && CONFIG_SCHED_LPNTHREADS > 0
+  /* Value of zero for period means that we should wait indefinitely until
+   * signalled.  This option is used only for the case where there are
+   * multiple, low-priority worker threads.  In that case, only one of
+   * the threads does the poll... the others simple.  In all other cases
+   * period will be non-zero and equal to wqueue->delay.
+   */
 
-  elapsed = clock_systimer() - stick;
+   if (period == 0)
-  if (elapsed <= wqueue->delay)
+     {
+       sigset_t set;
+
+       /* Wait indefinitely until signalled with SIGWORK */
+
+       sigemptyset(&set);
+       sigaddset(&set, SIGWORK);
+       DEBUGVERIFY(sigwaitinfo(&set, NULL));
+     }
+   else
+#endif
     {
-      /* How much time would we need to delay to get to the end of the
+      /* Get the delay (in clock ticks) since we started the sampling */
-       * sampling period?  The amount of time we delay should be the smaller
-       * of the time to the end of the sampling period and the time to the
-       * next work expiry.
-       */
 
-      remaining = wqueue->delay - elapsed;
+      elapsed = clock_systimer() - stick;
-      next      = MIN(next, remaining);
+      if (elapsed < period && next > 0)
-      if (next > 0)
         {
+          /* How much time would we need to delay to get to the end of the
+           * sampling period?  The amount of time we delay should be the smaller
+           * of the time to the end of the sampling period and the time to the
+           * next work expiry.
+           */
+
+          remaining = period - elapsed;
+          next      = MIN(next, remaining);
+
           /* Wait awhile to check the work list.  We will wait here until
            * either the time elapses or until we are awakened by a signal.
            * Interrupts will be re-enabled while we wait.

sched/wqueue/wqueue.h

@@ -180,13 +180,15 @@ int work_lpstart(void);
  *
  * Input parameters:
  *   wqueue - Describes the work queue to be processed
+ *   period - The polling period in clock ticks
+ *   wndx   - The worker thread index
  *
  * Returned Value:
  *   None
  *
  ****************************************************************************/
 
-void work_process(FAR struct kwork_wqueue_s *wqueue, int wndx);
+void work_process(FAR struct kwork_wqueue_s *wqueue, uint32_t period, int wndx);
 
 #endif /* CONFIG_SCHED_WORKQUEUE */
 #endif /* __SCHED_WQUEUE_WQUEUE_H */