Hi Qais,
On Wed, May 15, 2024 at 12:41:12AM +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 them with the new realtime_task() which returns true for RT and > DL classes - the old behavior. Introduce similar realtime_prio() to > create similar distinction to rt_prio() and update the users. I think making the difference clear is good. However, I think rt_task() is a better name. We have dl_task() still. And rt tasks are things managed by rt.c, basically. Not realtime.c :) I know that doesn't work for deadline.c and dl_ but this change would be the reverse of that pattern. > > 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 task_has_realtime_policy() as the old name > is confusing against the new realtime_task(). Keeping it rt_task() above could mean this stays as it was but this change makes sense as you have written it too. Cheers, Phil > > No functional changes were intended. > > [1] > https://lore.kernel.org/lkml/20240506100509.gl40...@noisy.programming.kicks-ass.net/ > > Signed-off-by: Qais Yousef <qyou...@layalina.io> > --- > fs/select.c | 2 +- > 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/fs/select.c b/fs/select.c > index 9515c3fa1a03..8d5c1419416c 100644 > --- a/fs/select.c > +++ b/fs/select.c > @@ -82,7 +82,7 @@ u64 select_estimate_accuracy(struct timespec64 *tv) > * Realtime tasks get a slack of 0 for obvious reasons. > */ > > - if (rt_task(current)) > + if (realtime_task(current)) > return 0; > > ktime_get_ts64(&now); > diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h > index db1249cd9692..6c00342b6166 100644 > --- a/include/linux/ioprio.h > +++ b/include/linux/ioprio.h > @@ -40,7 +40,7 @@ static inline int task_nice_ioclass(struct task_struct > *task) > { > if (task->policy == SCHED_IDLE) > return IOPRIO_CLASS_IDLE; > - else if (task_is_realtime(task)) > + else if (task_has_realtime_policy(task)) > return IOPRIO_CLASS_RT; > else > return IOPRIO_CLASS_BE; > diff --git a/include/linux/sched/deadline.h b/include/linux/sched/deadline.h > index df3aca89d4f5..5cb88b748ad6 100644 > --- a/include/linux/sched/deadline.h > +++ b/include/linux/sched/deadline.h > @@ -10,8 +10,6 @@ > > #include <linux/sched.h> > > -#define MAX_DL_PRIO 0 > - > static inline int dl_prio(int prio) > { > if (unlikely(prio < MAX_DL_PRIO)) > @@ -19,6 +17,10 @@ static inline int dl_prio(int prio) > return 0; > } > > +/* > + * Returns true if a task has a priority that belongs to DL class. PI-boosted > + * tasks will return true. Use dl_policy() to ignore PI-boosted tasks. > + */ > static inline int dl_task(struct task_struct *p) > { > return dl_prio(p->prio); > diff --git a/include/linux/sched/prio.h b/include/linux/sched/prio.h > index ab83d85e1183..6ab43b4f72f9 100644 > --- a/include/linux/sched/prio.h > +++ b/include/linux/sched/prio.h > @@ -14,6 +14,7 @@ > */ > > #define MAX_RT_PRIO 100 > +#define MAX_DL_PRIO 0 > > #define MAX_PRIO (MAX_RT_PRIO + NICE_WIDTH) > #define DEFAULT_PRIO (MAX_RT_PRIO + NICE_WIDTH / 2) > diff --git a/include/linux/sched/rt.h b/include/linux/sched/rt.h > index b2b9e6eb9683..b31be3c50152 100644 > --- a/include/linux/sched/rt.h > +++ b/include/linux/sched/rt.h > @@ -7,18 +7,43 @@ > struct task_struct; > > static inline int rt_prio(int prio) > +{ > + if (unlikely(prio < MAX_RT_PRIO && prio >= MAX_DL_PRIO)) > + return 1; > + return 0; > +} > + > +static inline int realtime_prio(int prio) > { > if (unlikely(prio < MAX_RT_PRIO)) > return 1; > return 0; > } > > +/* > + * Returns true if a task has a priority that belongs to RT class. PI-boosted > + * tasks will return true. Use rt_policy() to ignore PI-boosted tasks. > + */ > static inline int rt_task(struct task_struct *p) > { > return rt_prio(p->prio); > } > > -static inline bool task_is_realtime(struct task_struct *tsk) > +/* > + * Returns true if a task has a priority that belongs to RT or DL classes. > + * PI-boosted tasks will return true. Use task_has_realtime_policy() to > ignore > + * PI-boosted tasks. > + */ > +static inline int realtime_task(struct task_struct *p) > +{ > + return realtime_prio(p->prio); > +} > + > +/* > + * Returns true if a task has a policy that belongs to RT or DL classes. > + * PI-boosted tasks will return false. > + */ > +static inline bool task_has_realtime_policy(struct task_struct *tsk) > { > int policy = tsk->policy; > > diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c > index 88d08eeb8bc0..55c9dab37f33 100644 > --- a/kernel/locking/rtmutex.c > +++ b/kernel/locking/rtmutex.c > @@ -347,7 +347,7 @@ static __always_inline int __waiter_prio(struct > task_struct *task) > { > int prio = task->prio; > > - if (!rt_prio(prio)) > + if (!realtime_prio(prio)) > return DEFAULT_PRIO; > > return prio; > @@ -435,7 +435,7 @@ static inline bool rt_mutex_steal(struct rt_mutex_waiter > *waiter, > * Note that RT tasks are excluded from same priority (lateral) > * steals to prevent the introduction of an unbounded latency. > */ > - if (rt_prio(waiter->tree.prio) || dl_prio(waiter->tree.prio)) > + if (realtime_prio(waiter->tree.prio)) > return false; > > return rt_waiter_node_equal(&waiter->tree, &top_waiter->tree); > diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c > index c6d17aee4209..ad8d4438bc91 100644 > --- a/kernel/locking/rwsem.c > +++ b/kernel/locking/rwsem.c > @@ -631,7 +631,7 @@ static inline bool rwsem_try_write_lock(struct > rw_semaphore *sem, > * if it is an RT task or wait in the wait queue > * for too long. > */ > - if (has_handoff || (!rt_task(waiter->task) && > + if (has_handoff || (!realtime_task(waiter->task) && > !time_after(jiffies, > waiter->timeout))) > return false; > > @@ -914,7 +914,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore > *sem) > if (owner_state != OWNER_WRITER) { > if (need_resched()) > break; > - if (rt_task(current) && > + if (realtime_task(current) && > (prev_owner_state != OWNER_WRITER)) > break; > } > diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h > index 3ad2cc4823e5..fa4b416a1f62 100644 > --- a/kernel/locking/ww_mutex.h > +++ b/kernel/locking/ww_mutex.h > @@ -237,7 +237,7 @@ __ww_ctx_less(struct ww_acquire_ctx *a, struct > ww_acquire_ctx *b) > int a_prio = a->task->prio; > int b_prio = b->task->prio; > > - if (rt_prio(a_prio) || rt_prio(b_prio)) { > + if (realtime_prio(a_prio) || realtime_prio(b_prio)) { > > if (a_prio > b_prio) > return true; > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 1a914388144a..27f15de3d099 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -162,7 +162,7 @@ static inline int __task_prio(const struct task_struct *p) > if (p->sched_class == &stop_sched_class) /* trumps deadline */ > return -2; > > - if (rt_prio(p->prio)) /* includes deadline */ > + if (realtime_prio(p->prio)) /* includes deadline */ > return p->prio; /* [-1, 99] */ > > if (p->sched_class == &idle_sched_class) > @@ -2198,7 +2198,7 @@ static int effective_prio(struct task_struct *p) > * keep the priority unchanged. Otherwise, update priority > * to the normal priority: > */ > - if (!rt_prio(p->prio)) > + if (!realtime_prio(p->prio)) > return p->normal_prio; > return p->prio; > } > @@ -10282,7 +10282,7 @@ void normalize_rt_tasks(void) > schedstat_set(p->stats.sleep_start, 0); > schedstat_set(p->stats.block_start, 0); > > - if (!dl_task(p) && !rt_task(p)) { > + if (!realtime_task(p)) { > /* > * Renice negative nice level userspace > * tasks back to 0: > diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c > index 70625dff62ce..4150e98847fa 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 (task_has_realtime_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; > > 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; > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index 3e19b87049db..7372e40f225d 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -418,7 +418,7 @@ static void domain_dirty_limits(struct > dirty_throttle_control *dtc) > if (bg_thresh >= thresh) > bg_thresh = thresh / 2; > tsk = current; > - if (rt_task(tsk)) { > + if (realtime_task(tsk)) { > bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32; > thresh += thresh / 4 + global_wb_domain.dirty_limit / 32; > } > @@ -468,7 +468,7 @@ static unsigned long node_dirty_limit(struct pglist_data > *pgdat) > else > dirty = vm_dirty_ratio * node_memory / 100; > > - if (rt_task(tsk)) > + if (realtime_task(tsk)) > dirty += dirty / 4; > > return dirty; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 14d39f34d336..0af24a60ade0 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3877,7 +3877,7 @@ gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order) > */ > if (alloc_flags & ALLOC_MIN_RESERVE) > alloc_flags &= ~ALLOC_CPUSET; > - } else if (unlikely(rt_task(current)) && in_task()) > + } else if (unlikely(realtime_task(current)) && in_task()) > alloc_flags |= ALLOC_MIN_RESERVE; > > alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, alloc_flags); > -- > 2.34.1 > > --
