Since dequeue_task() allowed to fail, there is a compile error:

kernel/sched/ext.c:3630:19: error: initialization of ‘bool (*)(struct rq*, struct task_struct *, int)’ {aka ‘_Bool (*)(struct rq *, struct task_struct *, int)’} from incompatible pointer type ‘void (*)(struct rq*, struct task_struct *, int)’
  3630 |  .dequeue_task  = dequeue_task_scx,
       |                   ^~~~~~~~~~~~~~~~

Allow dequeue_task_scx to fail too.

Fixes: 863ccdbb918a ("sched: Allow sched_class::dequeue_task() to fail")
Signed-off-by: Yipeng Zou <zouyipeng@huawei.com>
---
 kernel/sched/ext.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 571a7ea0b5cb..b9bf9ee5ed01 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -2033,11 +2033,11 @@ static void ops_dequeue(struct task_struct *p, u64 deq_flags)
 	}
 }
 
-static void dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags)
+static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags)
 {
 	if (!(p->scx.flags & SCX_TASK_QUEUED)) {
 		WARN_ON_ONCE(task_runnable(p));
-		return;
+		return true;
 	}
 
 	ops_dequeue(p, deq_flags);
@@ -2072,6 +2072,7 @@ static void dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags
 	sub_nr_running(rq, 1);
 
 	dispatch_dequeue(rq, p);
+	return true;
 }
 
 static void yield_task_scx(struct rq *rq)
-- 
2.34.1

On Tue, Aug 20, 2024 at 10:45:31AM +0800, Yipeng Zou wrote:
> Since dequeue_task() allowed to fail, there is a compile error:
> 
> kernel/sched/ext.c:3630:19: error: initialization of ‘bool (*)(struct rq*, struct task_struct *, int)’ {aka ‘_Bool (*)(struct rq *, struct task_struct *, int)’} from incompatible pointer type ‘void (*)(struct rq*, struct task_struct *, int)’
>   3630 |  .dequeue_task  = dequeue_task_scx,
>        |                   ^~~~~~~~~~~~~~~~
> 
> Allow dequeue_task_scx to fail too.
> 
> Fixes: 863ccdbb918a ("sched: Allow sched_class::dequeue_task() to fail")
> Signed-off-by: Yipeng Zou <zouyipeng@huawei.com>

Applied to sched_ext/for-6.12.

Thanks.

-- 
tejun