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Wysocki" Cc: Christian Loehle , Linux PM , Thomas Gleixner , LKML , Peter Zijlstra , Frederic Weisbecker , Aboorva Devarajan Subject: Re: [PATCH v1] sched: idle: Make skipping governor callbacks more consistent Message-ID: <20260310035748.oum5mlscwh3tml7v@airbuntu> References: <20260301191959.406218221@kernel.org> <20260304030306.uk5c63xw4oqvjffb@airbuntu> <12857700.O9o76ZdvQC@rafael.j.wysocki> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On 03/09/26 13:26, Rafael J. Wysocki wrote: > On Mon, Mar 9, 2026 at 10:13 AM Christian Loehle > wrote: > > > > On 3/7/26 16:12, Rafael J. Wysocki wrote: > > > From: Rafael J. Wysocki > > > > > > If the cpuidle governor .select() callback is skipped because there > > > is only one idle state in the cpuidle driver, the .reflect() callback > > > should be skipped as well, at least for consistency (if not for > > > correctness), so do it. > > > > > > Fixes: e5c9ffc6ae1b ("cpuidle: Skip governor when only one idle state is available") > > > Signed-off-by: Rafael J. Wysocki > > > --- > > > drivers/cpuidle/cpuidle.c | 10 ---------- > > > kernel/sched/idle.c | 11 ++++++++++- > > > 2 files changed, 10 insertions(+), 11 deletions(-) > > > > > > --- a/drivers/cpuidle/cpuidle.c > > > +++ b/drivers/cpuidle/cpuidle.c > > > @@ -359,16 +359,6 @@ noinstr int cpuidle_enter_state(struct c > > > int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, > > > bool *stop_tick) > > > { > > > - /* > > > - * If there is only a single idle state (or none), there is nothing > > > - * meaningful for the governor to choose. Skip the governor and > > > - * always use state 0 with the tick running. > > > - */ > > > - if (drv->state_count <= 1) { > > > - *stop_tick = false; > > > - return 0; > > > - } > > > - > > > return cpuidle_curr_governor->select(drv, dev, stop_tick); > > > } > > > > > > --- a/kernel/sched/idle.c > > > +++ b/kernel/sched/idle.c > > > @@ -221,7 +221,7 @@ static void cpuidle_idle_call(void) > > > > > > next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns); > > > call_cpuidle(drv, dev, next_state); > > > - } else { > > > + } else if (drv->state_count > 1) { > > > bool stop_tick = true; > > > > > > /* > > > @@ -239,6 +239,15 @@ static void cpuidle_idle_call(void) > > > * Give the governor an opportunity to reflect on the outcome > > > */ > > > cpuidle_reflect(dev, entered_state); > > > + } else { > > > + tick_nohz_idle_retain_tick(); > > > + > > > + /* > > > + * If there is only a single idle state (or none), there is > > > + * nothing meaningful for the governor to choose. Skip the > > > + * governor and always use state 0. > > > + */ > > > + call_cpuidle(drv, dev, 0); > > > } > > > > > > exit_idle: > > > > > > > > > > > > > Duh, good catch. > > Reviewed-by: Christian Loehle > > OK, so any objections or concerns from anyone? > > I'm about to queue this up for the next -rc. LGTM too