On 2024-05-15 23:05:36 [+0100], Qais Yousef wrote: > rt_task() checks if a task has RT priority. But depends on your > dictionary, this could mean it belongs to RT class, or is a 'realtime' > task, which includes RT and DL classes. > > Since this has caused some confusion already on discussion [1], it > seemed a clean up is due. > > I define the usage of rt_task() to be tasks that belong to RT class. > Make sure that it returns true only for RT class and audit the users and > replace the ones required the old behavior with the new realtime_task() > which returns true for RT and DL classes. Introduce similar > realtime_prio() to create similar distinction to rt_prio() and update > the users that required the old behavior to use the new function. > > Move MAX_DL_PRIO to prio.h so it can be used in the new definitions. > > Document the functions to make it more obvious what is the difference > between them. PI-boosted tasks is a factor that must be taken into > account when choosing which function to use. > > Rename task_is_realtime() to realtime_task_policy() as the old name is > confusing against the new realtime_task(). I *think* everyone using rt_task() means to include DL tasks. And everyone means !SCHED-people since they know when the difference matters. > No functional changes were intended. > > [1] https://lore.kernel.org/lkml/20240506100509.GL40213@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > Reviewed-by: Phil Auld <pauld@xxxxxxxxxx> > Signed-off-by: Qais Yousef <qyousef@xxxxxxxxxxx> > --- > > Changes since v1: > > * Use realtime_task_policy() instead task_has_realtime_policy() (Peter) > * Improve commit message readability about replace some rt_task() > users. > > v1 discussion: https://lore.kernel.org/lkml/20240514234112.792989-1-qyousef@xxxxxxxxxxx/ > > fs/select.c | 2 +- fs/bcachefs/six.c six_owner_running() has rt_task(). But imho should have realtime_task() to consider DL. But I think it is way worse that it has its own locking rather than using what everyone else but then again it wouldn't be the new hot thing… > include/linux/ioprio.h | 2 +- > include/linux/sched/deadline.h | 6 ++++-- > include/linux/sched/prio.h | 1 + > include/linux/sched/rt.h | 27 ++++++++++++++++++++++++++- > kernel/locking/rtmutex.c | 4 ++-- > kernel/locking/rwsem.c | 4 ++-- > kernel/locking/ww_mutex.h | 2 +- > kernel/sched/core.c | 6 +++--- > kernel/time/hrtimer.c | 6 +++--- > kernel/trace/trace_sched_wakeup.c | 2 +- > mm/page-writeback.c | 4 ++-- > mm/page_alloc.c | 2 +- > 13 files changed, 48 insertions(+), 20 deletions(-) … > diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c > index 70625dff62ce..08b95e0a41ab 100644 > --- a/kernel/time/hrtimer.c > +++ b/kernel/time/hrtimer.c > @@ -1996,7 +1996,7 @@ static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl, > * expiry. > */ > if (IS_ENABLED(CONFIG_PREEMPT_RT)) { > - if (task_is_realtime(current) && !(mode & HRTIMER_MODE_SOFT)) > + if (realtime_task_policy(current) && !(mode & HRTIMER_MODE_SOFT)) > mode |= HRTIMER_MODE_HARD; > } > > @@ -2096,7 +2096,7 @@ long hrtimer_nanosleep(ktime_t rqtp, const enum hrtimer_mode mode, > u64 slack; > > slack = current->timer_slack_ns; > - if (rt_task(current)) > + if (realtime_task(current)) > slack = 0; > > hrtimer_init_sleeper_on_stack(&t, clockid, mode); > @@ -2301,7 +2301,7 @@ schedule_hrtimeout_range_clock(ktime_t *expires, u64 delta, > * Override any slack passed by the user if under > * rt contraints. > */ > - if (rt_task(current)) > + if (realtime_task(current)) > delta = 0; I know this is just converting what is already here but… __hrtimer_init_sleeper() looks at the policy to figure out if the task is realtime do decide if should expire in HARD-IRQ context. This is correct, a boosted task should not sleep. hrtimer_nanosleep() + schedule_hrtimeout_range_clock() is looking at priority to decide if slack should be removed. This should also look at policy since a boosted task shouldn't sleep. In order to be PI-boosted you need to acquire a lock and the only lock you can sleep while acquired without generating a warning is a mutex_t (or equivalent sleeping lock) on PREEMPT_RT. > hrtimer_init_sleeper_on_stack(&t, clock_id, mode); > diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c > index 0469a04a355f..19d737742e29 100644 > --- a/kernel/trace/trace_sched_wakeup.c > +++ b/kernel/trace/trace_sched_wakeup.c > @@ -545,7 +545,7 @@ probe_wakeup(void *ignore, struct task_struct *p) > * - wakeup_dl handles tasks belonging to sched_dl class only. > */ > if (tracing_dl || (wakeup_dl && !dl_task(p)) || > - (wakeup_rt && !dl_task(p) && !rt_task(p)) || > + (wakeup_rt && !realtime_task(p)) || > (!dl_task(p) && (p->prio >= wakeup_prio || p->prio >= current->prio))) > return; > Sebastian
