There are two problems with sched_server_write_common() that can cause the
dl_server to malfunction upon attempting to change the parameters:
1) when, after having disabled the dl_server by setting runtime=0, it is
enabled again while tasks are already enqueued. In this case is_active would
still be 0 and dl_server_start() would not be called.
2) when dl_server_apply_params() would fail, runtime is not applied and does
not reflect the new state.
Instead have dl_server_start() check its actual dl_runtime, and have
sched_server_write_common() unconditionally (re)start the dl_server. It will
automatically stop if there isn't anything to do, so spurious activation is
harmless -- while failing to start it is a problem.
While there, move the printk out of the locked region and make it symmetric,
also printing on enable.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260203103407.GK1282955@noisy.programming.kicks-ass.net
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