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ll-schedule: fix tasks removed during execution 

Zephyr LL-scheduler is supposed to be able to handle tasks, removed
or added while the scheduler is executing. However, there is a bug in
that implementation. If the task, that is currently executing, is
removed, its list head, that links it into the list of tasks, is
initialised. So when trying to get a pointer to the next task we
obtain a pointer to the same task.

BugLink: https://github.com/thesofproject/sof/issues/7084
Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
This commit is contained in:
Guennadi Liakhovetski 2023-02-21 15:15:07 +01:00 committed by Liam Girdwood
parent 0f0acaae94
commit 2b572c7d3b
1 changed files with 17 additions and 12 deletions
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29
src/schedule/zephyr_ll.c
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@ -162,19 +162,20 @@ static void zephyr_ll_run(void *data)
{
struct zephyr_ll *sch = data;
struct task *task;
struct list_item *list;
struct list_item *list, *tmp, task_head = LIST_INIT(task_head);
uint32_t flags;
zephyr_ll_lock(sch, &flags);
/*
* We have to traverse the list manually, because we drop the lock while
* executing tasks, at that time tasks can be removed from or added to
* the list.
* We drop the lock while executing tasks, at that time tasks can be
* removed from or added to the list, including the task that was
* executed. Use a temporary list to make sure that the main list is
* always consistent and contains the tasks, that we haven't run in this
* cycle yet.
*/
list = sch->tasks.next;
while (list != &sch->tasks) {
for (list = sch->tasks.next; !list_is_empty(&sch->tasks); list = sch->tasks.next) {
enum task_state state;
struct zephyr_ll_pdata *pdata;
@ -190,6 +191,10 @@ static void zephyr_ll_run(void *data)
pdata->run = true;
task->state = SOF_TASK_STATE_RUNNING;
/* Move the task to a temporary list */
list_item_del(list);
list_item_append(list, &task_head);
zephyr_ll_unlock(sch, &flags);
/*
@ -207,12 +212,6 @@ static void zephyr_ll_run(void *data)
zephyr_ll_lock(sch, &flags);
/*
* The .next pointer could've been changed while the lock wasn't
* held
*/
list = list->next;
if (pdata->freeing) {
/*
* zephyr_ll_task_free() is trying to free this task.
@ -238,6 +237,12 @@ static void zephyr_ll_run(void *data)
}
}
/* Move tasks back */
list_for_item_safe(list, tmp, &task_head) {
list_item_del(list);
list_item_append(list, &sch->tasks);
}
zephyr_ll_unlock(sch, &flags);
notifier_event(sch, NOTIFIER_ID_LL_POST_RUN,