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=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 0727FC433E0 for ; Fri, 22 Jan 2021 17:56:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C5AA223AA3 for ; Fri, 22 Jan 2021 17:56:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729654AbhAVRxY (ORCPT ); Fri, 22 Jan 2021 12:53:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37190 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729268AbhAVRmZ (ORCPT ); Fri, 22 Jan 2021 12:42:25 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A8FB4C061786; Fri, 22 Jan 2021 09:41:38 -0800 (PST) Date: Fri, 22 Jan 2021 17:41:35 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1611337296; 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=dVmXvrgapbqtA4yMCgRU8ljtEo5RGilDrQhFXdRg2N8=; b=pMmqwILygggI5IumqB07V4EVo0zNhQTPIje+pkEhxe1QXC4FM4zjUjjgXrj/1UiBbTQKdL LjdgB6DMiU8ONrkzh/DOt0y8bRSpLXEnEpk2Kj2zElKKaoRMseNnBu9ap7FufZX+qfLYgQ SMANQ/YjJ6YOBeEwJoF4f3b12gEWRPAPHAmyoHnpfPxWCzbdJI9Lj9O48flO+n6AGv/uen AULr8AXwAsc8Cw+VshEeDAVigsTutXfhP7xyP0JyeEDAYv5CqvHZ/3Cv9p79VJOyzEAebT BjHIj3y7uEZ9n4sPi7FcyUZwBa+YRG7I5dc2nbhkDE76wmXmTkbRUMdlhWY5TA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1611337296; 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=dVmXvrgapbqtA4yMCgRU8ljtEo5RGilDrQhFXdRg2N8=; b=W9wQDG7R8S4SQ6he2eUiQHfF/iT7cUiBkmTJyqrpcLObzj5KRhws3aeFy4FQFTSTaTz6Yy XC5xq+IDPOuWLXBQ== From: "tip-bot2 for Peter Zijlstra" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] kthread: Extract KTHREAD_IS_PER_CPU Cc: "Peter Zijlstra (Intel)" , Valentin Schneider , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210121103506.557620262@infradead.org> References: <20210121103506.557620262@infradead.org> MIME-Version: 1.0 Message-ID: <161133729574.414.5257210132156669609.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: 7bit 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: ac687e6e8c26181a33270efd1a2e2241377924b0 Gitweb: https://git.kernel.org/tip/ac687e6e8c26181a33270efd1a2e2241377924b0 Author: Peter Zijlstra AuthorDate: Tue, 12 Jan 2021 11:24:04 +01:00 Committer: Peter Zijlstra CommitterDate: Fri, 22 Jan 2021 15:09:42 +01:00 kthread: Extract KTHREAD_IS_PER_CPU There is a need to distinguish geniune per-cpu kthreads from kthreads that happen to have a single CPU affinity. Geniune per-cpu kthreads are kthreads that are CPU affine for correctness, these will obviously have PF_KTHREAD set, but must also have PF_NO_SETAFFINITY set, lest userspace modify their affinity and ruins things. However, these two things are not sufficient, PF_NO_SETAFFINITY is also set on other tasks that have their affinities controlled through other means, like for instance workqueues. Therefore another bit is needed; it turns out kthread_create_per_cpu() already has such a bit: KTHREAD_IS_PER_CPU, which is used to make kthread_park()/kthread_unpark() work correctly. Expose this flag and remove the implicit setting of it from kthread_create_on_cpu(); the io_uring usage of it seems dubious at best. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Tested-by: Valentin Schneider Link: https://lkml.kernel.org/r/20210121103506.557620262@infradead.org --- include/linux/kthread.h | 3 +++ kernel/kthread.c | 27 ++++++++++++++++++++++++++- kernel/smpboot.c | 1 + 3 files changed, 30 insertions(+), 1 deletion(-) diff --git a/include/linux/kthread.h b/include/linux/kthread.h index 65b81e0..2484ed9 100644 --- a/include/linux/kthread.h +++ b/include/linux/kthread.h @@ -33,6 +33,9 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data), unsigned int cpu, const char *namefmt); +void kthread_set_per_cpu(struct task_struct *k, int cpu); +bool kthread_is_per_cpu(struct task_struct *k); + /** * kthread_run - create and wake a thread. * @threadfn: the function to run until signal_pending(current). diff --git a/kernel/kthread.c b/kernel/kthread.c index a5eceec..e0e4a42 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -493,11 +493,36 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data), return p; kthread_bind(p, cpu); /* CPU hotplug need to bind once again when unparking the thread. */ - set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags); to_kthread(p)->cpu = cpu; return p; } +void kthread_set_per_cpu(struct task_struct *k, int cpu) +{ + struct kthread *kthread = to_kthread(k); + if (!kthread) + return; + + WARN_ON_ONCE(!(k->flags & PF_NO_SETAFFINITY)); + + if (cpu < 0) { + clear_bit(KTHREAD_IS_PER_CPU, &kthread->flags); + return; + } + + kthread->cpu = cpu; + set_bit(KTHREAD_IS_PER_CPU, &kthread->flags); +} + +bool kthread_is_per_cpu(struct task_struct *k) +{ + struct kthread *kthread = to_kthread(k); + if (!kthread) + return false; + + return test_bit(KTHREAD_IS_PER_CPU, &kthread->flags); +} + /** * kthread_unpark - unpark a thread created by kthread_create(). * @k: thread created by kthread_create(). diff --git a/kernel/smpboot.c b/kernel/smpboot.c index 2efe1e2..f25208e 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -188,6 +188,7 @@ __smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu) kfree(td); return PTR_ERR(tsk); } + kthread_set_per_cpu(tsk, cpu); /* * Park the thread so that it could start right on the CPU * when it is available.