diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup/rstat.c | 13 | ||||
| -rw-r--r-- | kernel/sched/ext.c | 72 |
2 files changed, 56 insertions, 29 deletions
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c index a198e40c799b..150e5871e66f 100644 --- a/kernel/cgroup/rstat.c +++ b/kernel/cgroup/rstat.c @@ -71,7 +71,6 @@ __bpf_kfunc void css_rstat_updated(struct cgroup_subsys_state *css, int cpu) { struct llist_head *lhead; struct css_rstat_cpu *rstatc; - struct css_rstat_cpu __percpu *rstatc_pcpu; struct llist_node *self; /* @@ -104,18 +103,22 @@ __bpf_kfunc void css_rstat_updated(struct cgroup_subsys_state *css, int cpu) /* * This function can be renentered by irqs and nmis for the same cgroup * and may try to insert the same per-cpu lnode into the llist. Note - * that llist_add() does not protect against such scenarios. + * that llist_add() does not protect against such scenarios. In addition + * this same per-cpu lnode can be modified through init_llist_node() + * from css_rstat_flush() running on a different CPU. * * To protect against such stacked contexts of irqs/nmis, we use the * fact that lnode points to itself when not on a list and then use - * this_cpu_cmpxchg() to atomically set to NULL to select the winner + * try_cmpxchg() to atomically set to NULL to select the winner * which will call llist_add(). The losers can assume the insertion is * successful and the winner will eventually add the per-cpu lnode to * the llist. + * + * Please note that we can not use this_cpu_cmpxchg() here as on some + * archs it is not safe against modifications from multiple CPUs. */ self = &rstatc->lnode; - rstatc_pcpu = css->rstat_cpu; - if (this_cpu_cmpxchg(rstatc_pcpu->lnode.next, self, NULL) != self) + if (!try_cmpxchg(&rstatc->lnode.next, &self, NULL)) return; lhead = ss_lhead_cpu(css->ss, cpu); diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 05f5a49e9649..94164f2dec6d 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -41,6 +41,13 @@ static bool scx_init_task_enabled; static bool scx_switching_all; DEFINE_STATIC_KEY_FALSE(__scx_switched_all); +/* + * Tracks whether scx_enable() called scx_bypass(true). Used to balance bypass + * depth on enable failure. Will be removed when bypass depth is moved into the + * sched instance. + */ +static bool scx_bypassed_for_enable; + static atomic_long_t scx_nr_rejected = ATOMIC_LONG_INIT(0); static atomic_long_t scx_hotplug_seq = ATOMIC_LONG_INIT(0); @@ -975,6 +982,30 @@ static void refill_task_slice_dfl(struct scx_sched *sch, struct task_struct *p) __scx_add_event(sch, SCX_EV_REFILL_SLICE_DFL, 1); } +static void local_dsq_post_enq(struct scx_dispatch_q *dsq, struct task_struct *p, + u64 enq_flags) +{ + struct rq *rq = container_of(dsq, struct rq, scx.local_dsq); + bool preempt = false; + + /* + * If @rq is in balance, the CPU is already vacant and looking for the + * next task to run. No need to preempt or trigger resched after moving + * @p into its local DSQ. + */ + if (rq->scx.flags & SCX_RQ_IN_BALANCE) + return; + + if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr && + rq->curr->sched_class == &ext_sched_class) { + rq->curr->scx.slice = 0; + preempt = true; + } + + if (preempt || sched_class_above(&ext_sched_class, rq->curr->sched_class)) + resched_curr(rq); +} + static void dispatch_enqueue(struct scx_sched *sch, struct scx_dispatch_q *dsq, struct task_struct *p, u64 enq_flags) { @@ -1086,22 +1117,10 @@ static void dispatch_enqueue(struct scx_sched *sch, struct scx_dispatch_q *dsq, if (enq_flags & SCX_ENQ_CLEAR_OPSS) atomic_long_set_release(&p->scx.ops_state, SCX_OPSS_NONE); - if (is_local) { - struct rq *rq = container_of(dsq, struct rq, scx.local_dsq); - bool preempt = false; - - if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr && - rq->curr->sched_class == &ext_sched_class) { - rq->curr->scx.slice = 0; - preempt = true; - } - - if (preempt || sched_class_above(&ext_sched_class, - rq->curr->sched_class)) - resched_curr(rq); - } else { + if (is_local) + local_dsq_post_enq(dsq, p, enq_flags); + else raw_spin_unlock(&dsq->lock); - } } static void task_unlink_from_dsq(struct task_struct *p, @@ -1625,6 +1644,8 @@ static void move_local_task_to_local_dsq(struct task_struct *p, u64 enq_flags, dsq_mod_nr(dst_dsq, 1); p->scx.dsq = dst_dsq; + + local_dsq_post_enq(dst_dsq, p, enq_flags); } /** @@ -2402,7 +2423,7 @@ static void put_prev_task_scx(struct rq *rq, struct task_struct *p, * ops.enqueue() that @p is the only one available for this cpu, * which should trigger an explicit follow-up scheduling event. */ - if (sched_class_above(&ext_sched_class, next->sched_class)) { + if (next && sched_class_above(&ext_sched_class, next->sched_class)) { WARN_ON_ONCE(!(sch->ops.flags & SCX_OPS_ENQ_LAST)); do_enqueue_task(rq, p, SCX_ENQ_LAST, -1); } else { @@ -2425,7 +2446,7 @@ static struct task_struct * do_pick_task_scx(struct rq *rq, struct rq_flags *rf, bool force_scx) { struct task_struct *prev = rq->curr; - bool keep_prev, kick_idle = false; + bool keep_prev; struct task_struct *p; /* see kick_cpus_irq_workfn() */ @@ -2467,12 +2488,8 @@ do_pick_task_scx(struct rq *rq, struct rq_flags *rf, bool force_scx) refill_task_slice_dfl(rcu_dereference_sched(scx_root), p); } else { p = first_local_task(rq); - if (!p) { - if (kick_idle) - scx_kick_cpu(rcu_dereference_sched(scx_root), - cpu_of(rq), SCX_KICK_IDLE); + if (!p) return NULL; - } if (unlikely(!p->scx.slice)) { struct scx_sched *sch = rcu_dereference_sched(scx_root); @@ -3575,7 +3592,7 @@ static void scx_sched_free_rcu_work(struct work_struct *work) int node; irq_work_sync(&sch->error_irq_work); - kthread_stop(sch->helper->task); + kthread_destroy_worker(sch->helper); free_percpu(sch->pcpu); @@ -4318,6 +4335,11 @@ static void scx_disable_workfn(struct kthread_work *work) scx_dsp_max_batch = 0; free_kick_syncs(); + if (scx_bypassed_for_enable) { + scx_bypassed_for_enable = false; + scx_bypass(false); + } + mutex_unlock(&scx_enable_mutex); WARN_ON_ONCE(scx_set_enable_state(SCX_DISABLED) != SCX_DISABLING); @@ -4786,7 +4808,7 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops) return sch; err_stop_helper: - kthread_stop(sch->helper->task); + kthread_destroy_worker(sch->helper); err_free_pcpu: free_percpu(sch->pcpu); err_free_gdsqs: @@ -4970,6 +4992,7 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link) * Init in bypass mode to guarantee forward progress. */ scx_bypass(true); + scx_bypassed_for_enable = true; for (i = SCX_OPI_NORMAL_BEGIN; i < SCX_OPI_NORMAL_END; i++) if (((void (**)(void))ops)[i]) @@ -5067,6 +5090,7 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link) scx_task_iter_stop(&sti); percpu_up_write(&scx_fork_rwsem); + scx_bypassed_for_enable = false; scx_bypass(false); if (!scx_tryset_enable_state(SCX_ENABLED, SCX_ENABLING)) { |