[1/3] idle: add support for tasks that inject idle

Message ID	1478718312-12847-2-git-send-email-jacob.jun.pan@linux.intel.com (mailing list archive)
State	Superseded, archived
Delegated to:	Zhang Rui
Headers	show Return-Path: <linux-pm-owner@kernel.org> From: Jacob Pan <jacob.jun.pan@linux.intel.com> To: LKML <linux-kernel@vger.kernel.org>, Linux PM <linux-pm@vger.kernel.org>, Peter Zijlstra <peterz@infradead.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com> Cc: Zhang Rui <rui.zhang@intel.com>, Rafael Wysocki <rafael.j.wysocki@intel.com>, "Chen, Yu C" <yu.c.chen@intel.com>, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, Petr Mladek <pmladek@suse.com>, Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>, Arjan van de Ven <arjan@linux.intel.com>, Jacob Pan <jacob.jun.pan@linux.intel.com> Subject: [PATCH 1/3] idle: add support for tasks that inject idle Date: Wed, 9 Nov 2016 11:05:10 -0800 Message-Id: <1478718312-12847-2-git-send-email-jacob.jun.pan@linux.intel.com> In-Reply-To: <1478718312-12847-1-git-send-email-jacob.jun.pan@linux.intel.com> References: <1478718312-12847-1-git-send-email-jacob.jun.pan@linux.intel.com> Sender: linux-pm-owner@vger.kernel.org Precedence: bulk

diff --git a/include/linux/cpu.h b/include/linux/cpu.h index b886dc1..9de0c4a 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -245,6 +245,8 @@ static inline void enable_nonboot_cpus(void) {} int cpu_report_state(int cpu); int cpu_check_up_prepare(int cpu); void cpu_set_state_online(int cpu); +void play_idle(void); + #ifdef CONFIG_HOTPLUG_CPU bool cpu_wait_death(unsigned int cpu, int seconds); bool cpu_report_death(void); diff --git a/include/linux/sched.h b/include/linux/sched.h index 348f51b..114c7fc 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2254,6 +2254,7 @@ static inline cputime_t task_gtime(struct task_struct *t) /* * Per process flags */ +#define PF_IDLE 0x00000002 /* I am an IDLE thread */ #define PF_EXITING 0x00000004 /* getting shut down */ #define PF_EXITPIDONE 0x00000008 /* pi exit done on shut down */ #define PF_VCPU 0x00000010 /* I'm a virtual CPU */ @@ -2609,7 +2610,7 @@ extern int sched_setattr(struct task_struct *, */ static inline bool is_idle_task(const struct task_struct *p) { - return p->pid == 0; + return !!(p->flags & PF_IDLE); } extern struct task_struct *curr_task(int cpu); extern void ia64_set_curr_task(int cpu, struct task_struct *p); diff --git a/kernel/fork.c b/kernel/fork.c index 997ac1d..73edbcd 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1819,6 +1819,9 @@ static __latent_entropy struct task_struct *copy_process( threadgroup_change_end(current); perf_event_fork(p); + /* do not inherit idle task */ + p->flags &= ~PF_IDLE; + trace_task_newtask(p, clone_flags); uprobe_copy_process(p, clone_flags); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 154fd68..c95fbcd 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5279,6 +5279,7 @@ void init_idle(struct task_struct *idle, int cpu) __sched_fork(0, idle); idle->state = TASK_RUNNING; idle->se.exec_start = sched_clock(); + idle->flags |= PF_IDLE; kasan_unpoison_task_stack(idle); diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 1d8718d..ffd9a83 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -202,76 +202,68 @@ static void cpuidle_idle_call(void) * * Called with polling cleared. */ -static void cpu_idle_loop(void) +static void do_idle(void) { - int cpu = smp_processor_id(); + /* + * If the arch has a polling bit, we maintain an invariant: + * + * Our polling bit is clear if we're not scheduled (i.e. if + * rq->curr != rq->idle). This means that, if rq->idle has + * the polling bit set, then setting need_resched is + * guaranteed to cause the cpu to reschedule. + */ - while (1) { - /* - * If the arch has a polling bit, we maintain an invariant: - * - * Our polling bit is clear if we're not scheduled (i.e. if - * rq->curr != rq->idle). This means that, if rq->idle has - * the polling bit set, then setting need_resched is - * guaranteed to cause the cpu to reschedule. - */ + __current_set_polling(); + tick_nohz_idle_enter(); - __current_set_polling(); - quiet_vmstat(); - tick_nohz_idle_enter(); - - while (!need_resched()) { - check_pgt_cache(); - rmb(); - - if (cpu_is_offline(cpu)) { - cpuhp_report_idle_dead(); - arch_cpu_idle_dead(); - } - - local_irq_disable(); - arch_cpu_idle_enter(); - - /* - * In poll mode we reenable interrupts and spin. - * - * Also if we detected in the wakeup from idle - * path that the tick broadcast device expired - * for us, we don't want to go deep idle as we - * know that the IPI is going to arrive right - * away - */ - if (cpu_idle_force_poll || tick_check_broadcast_expired()) - cpu_idle_poll(); - else - cpuidle_idle_call(); - - arch_cpu_idle_exit(); - } + while (!need_resched()) { + check_pgt_cache(); + rmb(); - /* - * Since we fell out of the loop above, we know - * TIF_NEED_RESCHED must be set, propagate it into - * PREEMPT_NEED_RESCHED. - * - * This is required because for polling idle loops we will - * not have had an IPI to fold the state for us. - */ - preempt_set_need_resched(); - tick_nohz_idle_exit(); - __current_clr_polling(); + if (cpu_is_offline(smp_processor_id())) { + cpuhp_report_idle_dead(); + arch_cpu_idle_dead(); + } - /* - * We promise to call sched_ttwu_pending and reschedule - * if need_resched is set while polling is set. That - * means that clearing polling needs to be visible - * before doing these things. - */ - smp_mb__after_atomic(); + local_irq_disable(); + arch_cpu_idle_enter(); - sched_ttwu_pending(); - schedule_preempt_disabled(); + /* In poll mode we reenable interrupts and spin. + * Also if we detected in the wakeup from idle + * path that the tick broadcast device expired + * for us, we don't want to go deep idle as we + * know that the IPI is going to arrive right + * away + */ + if (cpu_idle_force_poll || tick_check_broadcast_expired()) + cpu_idle_poll(); + else + cpuidle_idle_call(); + arch_cpu_idle_exit(); } + + /* + * Since we fell out of the loop above, we know + * TIF_NEED_RESCHED must be set, propagate it into + * PREEMPT_NEED_RESCHED. + * + * This is required because for polling idle loops we will + * not have had an IPI to fold the state for us. + */ + preempt_set_need_resched(); + tick_nohz_idle_exit(); + __current_clr_polling(); + + /* + * We promise to call sched_ttwu_pending and reschedule + * if need_resched is set while polling is set. That + * means that clearing polling needs to be visible + * before doing these things. + */ + smp_mb__after_atomic(); + + sched_ttwu_pending(); + schedule_preempt_disabled(); } bool cpu_in_idle(unsigned long pc) @@ -280,6 +272,28 @@ bool cpu_in_idle(unsigned long pc) pc < (unsigned long)__cpuidle_text_end; } +void play_idle() +{ + /* + * Only FIFO tasks can disable the tick since they don't need the forced + * preemption. + */ + WARN_ON_ONCE(current->policy != SCHED_FIFO); + WARN_ON_ONCE(current->nr_cpus_allowed != 1); + WARN_ON_ONCE(!(current->flags & PF_KTHREAD)); + WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY)); + rcu_sleep_check(); + + preempt_disable(); + current->flags |= PF_IDLE; + do_idle(); + current->flags &= ~PF_IDLE; + + preempt_fold_need_resched(); + preempt_enable(); +} +EXPORT_SYMBOL_GPL(play_idle); + void cpu_startup_entry(enum cpuhp_state state) { /* @@ -299,5 +313,7 @@ void cpu_startup_entry(enum cpuhp_state state) #endif arch_cpu_idle_prepare(); cpuhp_online_idle(state); - cpu_idle_loop(); + while (1) + do_idle(); + }

[1/3] idle: add support for tasks that inject idle

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