From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,UNWANTED_LANGUAGE_BODY,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C3FA4C43331 for ; Thu, 7 Nov 2019 19:29:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 851182087E for ; Thu, 7 Nov 2019 19:29:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Q+6/owWV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726916AbfKGT32 (ORCPT ); Thu, 7 Nov 2019 14:29:28 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:41154 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725871AbfKGT32 (ORCPT ); Thu, 7 Nov 2019 14:29:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=mruhdMayNO2zUrJBpiSsPdMto9fSfmHFCyz85Qb9jD0=; b=Q+6/owWVKe6k6WUgnm+Ib+p3c 3hxnrYfA186dZ63J3pmEtQWM+morOPU5k+tEUNA79jR3qvSOmJdTk7JDlKgi0c4oiOM5FAlXfFHU9 FhUxqh8KSIqfdKgwld38QlVuFa7nobj7MBspryjobC06DxTva9EnehBD39BMUZKGLUAjUkUjkAolx Gg9vC2w4yzeV6o0ONIbFKIfyHFYYhLV2WWIABKuze8sBfqMfhX6CDhY8W6Fw8S6DwZRnDequDN2vb NJS5MWpPM3tiZ7Rmhv9juCrdzdHSXP0S/REUtPVcR4W+qEt5y4SUkpFMMrFOVlp/NhMVnipPiassf BXGHO/2LA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iSnT1-0003EL-Tu; Thu, 07 Nov 2019 19:29:16 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 64E37980E2D; Thu, 7 Nov 2019 20:29:07 +0100 (CET) Date: Thu, 7 Nov 2019 20:29:07 +0100 From: Peter Zijlstra To: Quentin Perret Cc: Kirill Tkhai , linux-kernel@vger.kernel.org, aaron.lwe@gmail.com, valentin.schneider@arm.com, mingo@kernel.org, pauld@redhat.com, jdesfossez@digitalocean.com, naravamudan@digitalocean.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, juri.lelli@redhat.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, kernel-team@android.com, john.stultz@linaro.org Subject: Re: NULL pointer dereference in pick_next_task_fair Message-ID: <20191107192907.GA30258@worktop.programming.kicks-ass.net> References: <20191028174603.GA246917@google.com> <20191106120525.GX4131@hirez.programming.kicks-ass.net> <33643a5b-1b83-8605-2347-acd1aea04f93@virtuozzo.com> <20191106165437.GX4114@hirez.programming.kicks-ass.net> <20191106172737.GM5671@hirez.programming.kicks-ass.net> <831c2cd4-40a4-31b2-c0aa-b5f579e770d6@virtuozzo.com> <20191107132628.GZ4114@hirez.programming.kicks-ass.net> <20191107153848.GA31774@google.com> <20191107184356.GF4114@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191107184356.GF4114@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 07, 2019 at 07:43:56PM +0100, Peter Zijlstra wrote: > But you mean something like: > > for (class = prev->sched_class; class; class = class->next) { > if (class->balance(rq, rf)) > break; > } > > put_prev_task(rq, prev); > > for_each_class(class) { > p = class->pick_next_task(rq); > if (p) > return p; > } > > BUG(); > > like? I still havne't had food, but this here compiles... --- kernel/sched/core.c | 20 ++++++++++++-------- kernel/sched/deadline.c | 23 +++++++++++++++-------- kernel/sched/fair.c | 12 ++++++++++-- kernel/sched/idle.c | 8 +++++++- kernel/sched/rt.c | 32 +++++++++++++++++++------------- kernel/sched/sched.h | 5 +++-- kernel/sched/stop_task.c | 8 +++++++- 7 files changed, 73 insertions(+), 35 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index eb42b71faab9..d9909606806d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3929,13 +3929,17 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) } restart: - /* - * Ensure that we put DL/RT tasks before the pick loop, such that they - * can PULL higher prio tasks when we lower the RQ 'priority'. - */ - prev->sched_class->put_prev_task(rq, prev, rf); - if (!rq->nr_running) - newidle_balance(rq, rf); +#ifdef CONFIG_SMP + for (class = prev->sched_class; + class != &idle_sched_class; + class = class->next) { + + if (class->balance(rq, prev, rf)) + break; + } +#endif + + put_prev_task(rq, prev); for_each_class(class) { p = class->pick_next_task(rq, NULL, NULL); @@ -6201,7 +6205,7 @@ static struct task_struct *__pick_migrate_task(struct rq *rq) for_each_class(class) { next = class->pick_next_task(rq, NULL, NULL); if (next) { - next->sched_class->put_prev_task(rq, next, NULL); + next->sched_class->put_prev_task(rq, next); return next; } } diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 2dc48720f189..b6c3fb10cf57 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1778,15 +1778,9 @@ pick_next_task_dl(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) return p; } -static void put_prev_task_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf) +static int balance_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf) { - update_curr_dl(rq); - - update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1); - if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1) - enqueue_pushable_dl_task(rq, p); - - if (rf && !on_dl_rq(&p->dl) && need_pull_dl_task(rq, p)) { + if (!on_dl_rq(&p->dl) && need_pull_dl_task(rq, p)) { /* * This is OK, because current is on_cpu, which avoids it being * picked for load-balance and preemption/IRQs are still @@ -1797,6 +1791,18 @@ static void put_prev_task_dl(struct rq *rq, struct task_struct *p, struct rq_fla pull_dl_task(rq); rq_repin_lock(rq, rf); } + + return rq->dl.dl_nr_running > 0; +} + + +static void put_prev_task_dl(struct rq *rq, struct task_struct *p) +{ + update_curr_dl(rq); + + update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1); + if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1) + enqueue_pushable_dl_task(rq, p); } /* @@ -2438,6 +2444,7 @@ const struct sched_class dl_sched_class = { .check_preempt_curr = check_preempt_curr_dl, .pick_next_task = pick_next_task_dl, + .balance = balance_dl, .put_prev_task = put_prev_task_dl, .set_next_task = set_next_task_dl, diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a14487462b6c..6b983214e00f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6746,10 +6746,18 @@ done: __maybe_unused; return NULL; } +static int balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) +{ + if (rq->cfs.nr_running) + return 1; + + return newidle_balance(rq, rf) != 0; +} + /* * Account for a descheduled task: */ -static void put_prev_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) +static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) { struct sched_entity *se = &prev->se; struct cfs_rq *cfs_rq; @@ -10609,7 +10617,7 @@ const struct sched_class fair_sched_class = { .check_preempt_curr = check_preempt_wakeup, .pick_next_task = pick_next_task_fair, - + .balance = balance_fair, .put_prev_task = put_prev_task_fair, .set_next_task = set_next_task_fair, diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 8dad5aa600ea..2ff65fd2fe7e 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -375,7 +375,12 @@ static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int fl resched_curr(rq); } -static void put_prev_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) +static int balance_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) +{ + return 1; /* always runnable */ +} + +static void put_prev_task_idle(struct rq *rq, struct task_struct *prev) { } @@ -456,6 +461,7 @@ const struct sched_class idle_sched_class = { .check_preempt_curr = check_preempt_curr_idle, .pick_next_task = pick_next_task_idle, + .balance = balance_idle, .put_prev_task = put_prev_task_idle, .set_next_task = set_next_task_idle, diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index ebaa4e619684..3aa3e0fca796 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1566,20 +1566,9 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) return p; } -static void put_prev_task_rt(struct rq *rq, struct task_struct *p, struct rq_flags *rf) +static int balance_rt(struct rq *rq, struct task_struct *p, struct rq_flags *rf) { - update_curr_rt(rq); - - update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1); - - /* - * The previous task needs to be made eligible for pushing - * if it is still active - */ - if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1) - enqueue_pushable_task(rq, p); - - if (rf && !on_rt_rq(&p->rt) && need_pull_rt_task(rq, p)) { + if (!on_rt_rq(&p->rt) && need_pull_rt_task(rq, p)) { /* * This is OK, because current is on_cpu, which avoids it being * picked for load-balance and preemption/IRQs are still @@ -1590,6 +1579,22 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p, struct rq_fla pull_rt_task(rq); rq_repin_lock(rq, rf); } + + return rq->rt.rt_queued > 0; +} + +static void put_prev_task_rt(struct rq *rq, struct task_struct *p) +{ + update_curr_rt(rq); + + update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1); + + /* + * The previous task needs to be made eligible for pushing + * if it is still active + */ + if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1) + enqueue_pushable_task(rq, p); } #ifdef CONFIG_SMP @@ -2362,6 +2367,7 @@ const struct sched_class rt_sched_class = { .check_preempt_curr = check_preempt_curr_rt, .pick_next_task = pick_next_task_rt, + .balance = balance_rt, .put_prev_task = put_prev_task_rt, .set_next_task = set_next_task_rt, diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 0db2c1b3361e..3b50450428dc 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1727,7 +1727,8 @@ struct sched_class { struct task_struct * (*pick_next_task)(struct rq *rq, struct task_struct *prev, struct rq_flags *rf); - void (*put_prev_task)(struct rq *rq, struct task_struct *p, struct rq_flags *rf); + int (*balance)(struct rq *rq, struct task_struct *prev, struct rq_flags *rf); + void (*put_prev_task)(struct rq *rq, struct task_struct *p); void (*set_next_task)(struct rq *rq, struct task_struct *p); #ifdef CONFIG_SMP @@ -1773,7 +1774,7 @@ struct sched_class { static inline void put_prev_task(struct rq *rq, struct task_struct *prev) { WARN_ON_ONCE(rq->curr != prev); - prev->sched_class->put_prev_task(rq, prev, NULL); + prev->sched_class->put_prev_task(rq, prev); } static inline void set_next_task(struct rq *rq, struct task_struct *next) diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c index 7e1cee4e65b2..8a5b3e5540ee 100644 --- a/kernel/sched/stop_task.c +++ b/kernel/sched/stop_task.c @@ -60,7 +60,12 @@ static void yield_task_stop(struct rq *rq) BUG(); /* the stop task should never yield, its pointless. */ } -static void put_prev_task_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) +static int balance_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) +{ + return 0; +} + +static void put_prev_task_stop(struct rq *rq, struct task_struct *prev) { struct task_struct *curr = rq->curr; u64 delta_exec; @@ -125,6 +130,7 @@ const struct sched_class stop_sched_class = { .check_preempt_curr = check_preempt_curr_stop, .pick_next_task = pick_next_task_stop, + .balance = balance_stop, .put_prev_task = put_prev_task_stop, .set_next_task = set_next_task_stop,