sched_ext: Fix missing warning in scx_set_task_state() default case

In scx_set_task_state(), the default case was setting the
warn flag, but then returning immediately. This is problematic
because the only purpose of the warn flag is to trigger
WARN_ONCE, but the early return prevented it from ever firing,
leaving invalid task states undetected and untraced.

To fix this, a WARN_ONCE call is now added directly in the
default case.

The fix addresses two aspects:

 - Guarantees the invalid task states are properly logged
   and traced.

 - Provides a distinct warning message
   ("sched_ext: Invalid task state") specifically for
   states outside the defined scx_task_state enum values,
   making it easier to distinguish from other transition
   warnings.

This ensures proper detection and reporting of invalid states.

Signed-off-by: Samuele Mariotti <smariotti@disroot.org>
Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 9628c64e5592ae8285aece5bbd977738b0ae57c8..0253887e63c0387479f33739e73a8f0cac07c73f 100644 (file)
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3538,7 +3538,8 @@ static void scx_set_task_state(struct task_struct *p, u32 state)
                warn = prev_state != SCX_TASK_READY;
                break;
        default:
-               warn = true;
+               WARN_ONCE(1, "sched_ext: Invalid task state %d -> %d for %s[%d]",
+                         prev_state, state, p->comm, p->pid);
                return;
        }