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McKenney" , Tim Chen Subject: [PATCH v8 -tip 02/26] sched: Introduce sched_class::pick_task() Date: Mon, 19 Oct 2020 21:43:12 -0400 Message-Id: <20201020014336.2076526-3-joel@joelfernandes.org> X-Mailer: git-send-email 2.29.0.rc1.297.gfa9743e501-goog In-Reply-To: <20201020014336.2076526-1-joel@joelfernandes.org> References: <20201020014336.2076526-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra Because sched_class::pick_next_task() also implies sched_class::set_next_task() (and possibly put_prev_task() and newidle_balance) it is not state invariant. This makes it unsuitable for remote task selection. Tested-by: Julien Desfossez Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Vineeth Remanan Pillai Signed-off-by: Julien Desfossez Signed-off-by: Joel Fernandes (Google) --- kernel/sched/deadline.c | 16 ++++++++++++++-- kernel/sched/fair.c | 32 +++++++++++++++++++++++++++++++- kernel/sched/idle.c | 8 ++++++++ kernel/sched/rt.c | 14 ++++++++++++-- kernel/sched/sched.h | 3 +++ kernel/sched/stop_task.c | 13 +++++++++++-- 6 files changed, 79 insertions(+), 7 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 814ec49502b1..0271a7848ab3 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1848,7 +1848,7 @@ static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq, return rb_entry(left, struct sched_dl_entity, rb_node); } -static struct task_struct *pick_next_task_dl(struct rq *rq) +static struct task_struct *pick_task_dl(struct rq *rq) { struct sched_dl_entity *dl_se; struct dl_rq *dl_rq = &rq->dl; @@ -1860,7 +1860,18 @@ static struct task_struct *pick_next_task_dl(struct rq *rq) dl_se = pick_next_dl_entity(rq, dl_rq); BUG_ON(!dl_se); p = dl_task_of(dl_se); - set_next_task_dl(rq, p, true); + + return p; +} + +static struct task_struct *pick_next_task_dl(struct rq *rq) +{ + struct task_struct *p; + + p = pick_task_dl(rq); + if (p) + set_next_task_dl(rq, p, true); + return p; } @@ -2517,6 +2528,7 @@ const struct sched_class dl_sched_class #ifdef CONFIG_SMP .balance = balance_dl, + .pick_task = pick_task_dl, .select_task_rq = select_task_rq_dl, .migrate_task_rq = migrate_task_rq_dl, .set_cpus_allowed = set_cpus_allowed_dl, diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index dbd9368a959d..bd6aed63f5e3 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4450,7 +4450,7 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) * Avoid running the skip buddy, if running something else can * be done without getting too unfair. */ - if (cfs_rq->skip == se) { + if (cfs_rq->skip && cfs_rq->skip == se) { struct sched_entity *second; if (se == curr) { @@ -6976,6 +6976,35 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ set_last_buddy(se); } +#ifdef CONFIG_SMP +static struct task_struct *pick_task_fair(struct rq *rq) +{ + struct cfs_rq *cfs_rq = &rq->cfs; + struct sched_entity *se; + + if (!cfs_rq->nr_running) + return NULL; + + do { + struct sched_entity *curr = cfs_rq->curr; + + se = pick_next_entity(cfs_rq, NULL); + + if (curr) { + if (se && curr->on_rq) + update_curr(cfs_rq); + + if (!se || entity_before(curr, se)) + se = curr; + } + + cfs_rq = group_cfs_rq(se); + } while (cfs_rq); + + return task_of(se); +} +#endif + struct task_struct * pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { @@ -11173,6 +11202,7 @@ const struct sched_class fair_sched_class #ifdef CONFIG_SMP .balance = balance_fair, + .pick_task = pick_task_fair, .select_task_rq = select_task_rq_fair, .migrate_task_rq = migrate_task_rq_fair, diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 8ce6e80352cf..ce7552c6bc65 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -405,6 +405,13 @@ static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool fir schedstat_inc(rq->sched_goidle); } +#ifdef CONFIG_SMP +static struct task_struct *pick_task_idle(struct rq *rq) +{ + return rq->idle; +} +#endif + struct task_struct *pick_next_task_idle(struct rq *rq) { struct task_struct *next = rq->idle; @@ -472,6 +479,7 @@ const struct sched_class idle_sched_class #ifdef CONFIG_SMP .balance = balance_idle, + .pick_task = pick_task_idle, .select_task_rq = select_task_rq_idle, .set_cpus_allowed = set_cpus_allowed_common, #endif diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index e57fca05b660..a5851c775270 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1624,7 +1624,7 @@ static struct task_struct *_pick_next_task_rt(struct rq *rq) return rt_task_of(rt_se); } -static struct task_struct *pick_next_task_rt(struct rq *rq) +static struct task_struct *pick_task_rt(struct rq *rq) { struct task_struct *p; @@ -1632,7 +1632,16 @@ static struct task_struct *pick_next_task_rt(struct rq *rq) return NULL; p = _pick_next_task_rt(rq); - set_next_task_rt(rq, p, true); + + return p; +} + +static struct task_struct *pick_next_task_rt(struct rq *rq) +{ + struct task_struct *p = pick_task_rt(rq); + if (p) + set_next_task_rt(rq, p, true); + return p; } @@ -2443,6 +2452,7 @@ const struct sched_class rt_sched_class #ifdef CONFIG_SMP .balance = balance_rt, + .pick_task = pick_task_rt, .select_task_rq = select_task_rq_rt, .set_cpus_allowed = set_cpus_allowed_common, .rq_online = rq_online_rt, diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 587ebabebaff..54bfac702805 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1800,6 +1800,9 @@ struct sched_class { #ifdef CONFIG_SMP int (*balance)(struct rq *rq, struct task_struct *prev, struct rq_flags *rf); + + struct task_struct * (*pick_task)(struct rq *rq); + int (*select_task_rq)(struct task_struct *p, int task_cpu, int sd_flag, int flags); void (*migrate_task_rq)(struct task_struct *p, int new_cpu); diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c index 394bc8126a1e..8f92915dd95e 100644 --- a/kernel/sched/stop_task.c +++ b/kernel/sched/stop_task.c @@ -34,15 +34,23 @@ static void set_next_task_stop(struct rq *rq, struct task_struct *stop, bool fir stop->se.exec_start = rq_clock_task(rq); } -static struct task_struct *pick_next_task_stop(struct rq *rq) +static struct task_struct *pick_task_stop(struct rq *rq) { if (!sched_stop_runnable(rq)) return NULL; - set_next_task_stop(rq, rq->stop, true); return rq->stop; } +static struct task_struct *pick_next_task_stop(struct rq *rq) +{ + struct task_struct *p = pick_task_stop(rq); + if (p) + set_next_task_stop(rq, p, true); + + return p; +} + static void enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags) { @@ -124,6 +132,7 @@ const struct sched_class stop_sched_class #ifdef CONFIG_SMP .balance = balance_stop, + .pick_task = pick_task_stop, .select_task_rq = select_task_rq_stop, .set_cpus_allowed = set_cpus_allowed_common, #endif -- 2.29.0.rc1.297.gfa9743e501-goog