sched/debug: Stop and start server based on if it was active

Currently the DL server interface for applying parameters checks
CFS-internals to identify if the server is active. This is error-prone
and makes it difficult when adding new servers in the future.

Fix it, by using dl_server_active() which is also used by the DL server
code to determine if the DL server was started.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Acked-by: Tejun Heo <tj@kernel.org>
Tested-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/20260126100050.3854740-4-arighi@nvidia.com

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index ed9254da511613f9c5dba2e48f2ffae0acfe5938..41e389569d06b54260c819669ab63fd432fbad75 100644 (file)
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -348,6 +348,8 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
                return err;
 
        scoped_guard (rq_lock_irqsave, rq) {
+               bool is_active;
+
                runtime  = rq->fair_server.dl_runtime;
                period = rq->fair_server.dl_period;
 
@@ -370,8 +372,11 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
                        return  -EINVAL;
                }
 
-               update_rq_clock(rq);
-               dl_server_stop(&rq->fair_server);
+               is_active = dl_server_active(&rq->fair_server);
+               if (is_active) {
+                       update_rq_clock(rq);
+                       dl_server_stop(&rq->fair_server);
+               }
 
                retval = dl_server_apply_params(&rq->fair_server, runtime, period, 0);
 
@@ -379,7 +384,7 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
                        printk_deferred("Fair server disabled in CPU %d, system may crash due to starvation.\n",
                                        cpu_of(rq));
 
-               if (rq->cfs.h_nr_queued)
+               if (is_active && runtime)
                        dl_server_start(&rq->fair_server);
 
                if (retval < 0)