On 26.06.2024 07:54, Juergen Gross wrote:
In case cpu_schedule_up() is failing, it needs to undo all externally
visible changes it has done before.
Reason is that cpu_schedule_callback() won't be called with the
CPU_UP_CANCELED notifier in case cpu_schedule_up() did fail.
Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
Fixes: 207589dbacd4 ("xen/sched: move per cpu scheduler private data into struct
sched_resource")
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with two questions, just for my own reassurance:
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -2755,6 +2755,36 @@ static struct sched_resource *sched_alloc_res(void)
return sr;
}
+static void cf_check sched_res_free(struct rcu_head *head)
+{
+ struct sched_resource *sr = container_of(head, struct sched_resource, rcu);
+
+ free_cpumask_var(sr->cpus);
+ if ( sr->sched_unit_idle )
+ sched_free_unit_mem(sr->sched_unit_idle);
+ xfree(sr);
+}
+
+static void cpu_schedule_down(unsigned int cpu)
+{
+ struct sched_resource *sr;
+
+ rcu_read_lock(&sched_res_rculock);
+
+ sr = get_sched_res(cpu);
+
+ kill_timer(&sr->s_timer);
+
+ cpumask_clear_cpu(cpu, &sched_res_mask);
+ set_sched_res(cpu, NULL);
+
+ /* Keep idle unit. */
+ sr->sched_unit_idle = NULL;
+ call_rcu(&sr->rcu, sched_res_free);
+
+ rcu_read_unlock(&sched_res_rculock);
+}
Eyeballing suggests these two functions don't change at all; they're solely
being moved up?
Also, for the purpose here, use of RCU to effect the freeing isn't strictly
necessary. It's just that it also doesn't hurt doing it that way, and it
would be more code to directly free when coming from cpu_schedule_up()?
