jlaitine commented on code in PR #16673:
URL: https://github.com/apache/nuttx/pull/16673#discussion_r2196997364
##########
sched/sched/sched_mergepending.c:
##########
@@ -186,100 +186,97 @@ bool nxsched_merge_pending(void)
****************************************************************************/
#ifdef CONFIG_SMP
+
bool nxsched_merge_pending(void)
{
FAR struct tcb_s *rtcb;
FAR struct tcb_s *ptcb;
- FAR struct tcb_s *tcb;
+ FAR struct tcb_s *next;
bool ret = false;
int cpu;
+ int minprio;
- /* Remove and process every TCB in the g_pendingtasks list.
- *
- * Do nothing if (1) pre-emption is still disabled (by any CPU), or (2) if
- * some CPU other than this one is in a critical section.
- */
+ ptcb = (FAR struct tcb_s *)dq_peek(list_readytorun());
+ if (ptcb == NULL)
+ {
+ /* The readytorun task list is empty. */
+
+ return false;
+ }
+
+ /* Find the CPU that is executing the lowest priority task. */
- if (!nxsched_islocked_tcb(this_task()))
+ cpu = nxsched_select_cpu(ALL_CPUS);
+ if (cpu >= CONFIG_SMP_NCPUS)
{
- /* Find the CPU that is executing the lowest priority task */
+ /* There are no available CPUs. This can only happen if
+ * all the CPUs are running scheduler locked
+ */
- ptcb = (FAR struct tcb_s *)dq_peek(list_pendingtasks());
- if (ptcb == NULL)
- {
- /* The pending task list is empty */
+ return false;
+ }
- return false;
- }
+ rtcb = current_delivered(cpu);
+ minprio = rtcb->sched_priority;
- cpu = nxsched_select_cpu(ALL_CPUS); /* REVISIT: Maybe ptcb->affinity */
- rtcb = current_task(cpu);
+ /* Loop while there is a higher priority task in the ready-to-run list
+ * than in the lowest executing task.
+ *
+ * Normally, this loop should execute no more than CONFIG_SMP_NCPUS
+ * times. That number could be larger, however, if the CPU affinity
+ * sets do not include all CPUs. In that case, the excess TCBs will
+ * be left in the g_readytorun list.
+ */
- /* Loop while there is a higher priority task in the pending task list
- * than in the lowest executing task.
- *
- * Normally, this loop should execute no more than CONFIG_SMP_NCPUS
- * times. That number could be larger, however, if the CPU affinity
- * sets do not include all CPUs. In that case, the excess TCBs will
- * end up in the g_readytorun list.
+ while (ptcb && ptcb->sched_priority > minprio)
+ {
+ /* If the ptcb is not allowed to run on this CPU, re-select the
+ * CPU. This is unlikely, so re-select is not worth doing on
+ * every cycle.
*/
- while (ptcb->sched_priority > rtcb->sched_priority)
+ if (((1 << cpu) & ptcb->affinity) == 0)
{
- /* Remove the task from the pending task list */
-
- tcb = (FAR struct tcb_s *)dq_remfirst(list_pendingtasks());
-
- /* Add the pending task to the correct ready-to-run list. */
+ cpu = nxsched_select_cpu(ptcb->affinity);
+ if (cpu >= CONFIG_SMP_NCPUS)
+ {
+ /* No available CPUs to run this task, try next one */
- ret |= nxsched_add_readytorun(tcb);
+ continue;
Review Comment:
This is a bug, would be an infinite loop. Will fix....
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