From nobody Fri Apr 10 01:38:41 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2AA5DC54EBE for ; Mon, 9 Jan 2023 10:46:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233399AbjAIKqS (ORCPT ); Mon, 9 Jan 2023 05:46:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53418 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234288AbjAIKpx (ORCPT ); Mon, 9 Jan 2023 05:45:53 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A5652615; Mon, 9 Jan 2023 02:45:52 -0800 (PST) Date: Mon, 09 Jan 2023 10:45:49 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1673261150; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BPZb9ukPZTcxAtrvj1QdbsugeI7W3VLo/9zdEGtVAGw=; b=dH5FwsqqlyRCwg3sN9ZpbF3c+X3DE5SyVn32kURsg0bAqT5QaUKUmKbz68nhFB0kJIQHkr PNNQDoa4nibUmYhuHUxJd572YSSpx5gd0rGefy7lZ9esMdoM/L5qcnEWKrEnQj2kl7i7DK q3BhvVCAU0mE3nXTbCiH1oVlnk0ols711r3GTh7tXuqpnhW4NYsZ5tfSAIzSwYDbJrJ3dK mSWpNEvTon5zKxGJ8q3xlw7hqx85521MJX+lATzQ32VVSQiNQ75Pq9ck9+wcyzwb2JEYWw iyPrqdUFbyPG0w52mXuU1WGFoRYiWos6E/xkeIWONgNcA+jJLSjGJHAu7ZgZSw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1673261150; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BPZb9ukPZTcxAtrvj1QdbsugeI7W3VLo/9zdEGtVAGw=; b=/G6eqSBW1UBko61m+yk6ua8qoRdcvRGfjqztX+pEu/Di6+K71vq8429WWZYK0zuc8KiF75 OOIAOcUBed9ijDCA== From: "tip-bot2 for Waiman Long" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] sched/core: Use kfree_rcu() in do_set_cpus_allowed() Cc: Peter Zijlstra , Waiman Long , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20221231041120.440785-3-longman@redhat.com> References: <20221231041120.440785-3-longman@redhat.com> MIME-Version: 1.0 Message-ID: <167326114997.4906.573601630756814284.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/urgent branch of tip: Commit-ID: 9a5418bc48babb313d2a62df29ebe21ce8c06c59 Gitweb: https://git.kernel.org/tip/9a5418bc48babb313d2a62df29ebe21ce= 8c06c59 Author: Waiman Long AuthorDate: Fri, 30 Dec 2022 23:11:20 -05:00 Committer: Ingo Molnar CommitterDate: Mon, 09 Jan 2023 11:43:23 +01:00 sched/core: Use kfree_rcu() in do_set_cpus_allowed() Commit 851a723e45d1 ("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()") may call kfree() if user_cpus_ptr was previously set. Unfortunately, some of the callers of do_set_cpus_allowed() may have pi_lock held when calling it. So the following splats may be printed especially when running with a PREEMPT_RT kernel: WARNING: possible circular locking dependency detected BUG: sleeping function called from invalid context To avoid these problems, kfree_rcu() is used instead. An internal cpumask_rcuhead union is created for the sole purpose of facilitating the use of kfree_rcu() to free the cpumask. Since user_cpus_ptr is not being used in non-SMP configs, the newly introduced alloc_user_cpus_ptr() helper will return NULL in this case and sched_setaffinity() is modified to handle this special case. Fixes: 851a723e45d1 ("sched: Always clear user_cpus_ptr in do_set_cpus_allo= wed()") Suggested-by: Peter Zijlstra Signed-off-by: Waiman Long Signed-off-by: Ingo Molnar Reviewed-by: Peter Zijlstra Link: https://lore.kernel.org/r/20221231041120.440785-3-longman@redhat.com --- kernel/sched/core.c | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f9f6e54..bb1ee6d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2604,9 +2604,29 @@ void do_set_cpus_allowed(struct task_struct *p, cons= t struct cpumask *new_mask) .user_mask =3D NULL, .flags =3D SCA_USER, /* clear the user requested mask */ }; + union cpumask_rcuhead { + cpumask_t cpumask; + struct rcu_head rcu; + }; =20 __do_set_cpus_allowed(p, &ac); - kfree(ac.user_mask); + + /* + * Because this is called with p->pi_lock held, it is not possible + * to use kfree() here (when PREEMPT_RT=3Dy), therefore punt to using + * kfree_rcu(). + */ + kfree_rcu((union cpumask_rcuhead *)ac.user_mask, rcu); +} + +static cpumask_t *alloc_user_cpus_ptr(int node) +{ + /* + * See do_set_cpus_allowed() above for the rcu_head usage. + */ + int size =3D max_t(int, cpumask_size(), sizeof(struct rcu_head)); + + return kmalloc_node(size, GFP_KERNEL, node); } =20 int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src, @@ -2629,7 +2649,7 @@ int dup_user_cpus_ptr(struct task_struct *dst, struct= task_struct *src, if (data_race(!src->user_cpus_ptr)) return 0; =20 - user_mask =3D kmalloc_node(cpumask_size(), GFP_KERNEL, node); + user_mask =3D alloc_user_cpus_ptr(node); if (!user_mask) return -ENOMEM; =20 @@ -3605,6 +3625,11 @@ static inline bool rq_has_pinned_tasks(struct rq *rq) return false; } =20 +static inline cpumask_t *alloc_user_cpus_ptr(int node) +{ + return NULL; +} + #endif /* !CONFIG_SMP */ =20 static void @@ -8265,8 +8290,8 @@ long sched_setaffinity(pid_t pid, const struct cpumas= k *in_mask) if (retval) goto out_put_task; =20 - user_mask =3D kmalloc(cpumask_size(), GFP_KERNEL); - if (!user_mask) { + user_mask =3D alloc_user_cpus_ptr(NUMA_NO_NODE); + if (IS_ENABLED(CONFIG_SMP) && !user_mask) { retval =3D -ENOMEM; goto out_put_task; }