From patchwork Mon Mar 1 16:14:07 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 389135 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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT 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 576B4C433DB for ; Mon, 1 Mar 2021 20:29:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1EC8F60235 for ; Mon, 1 Mar 2021 20:29:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242298AbhCAU1g (ORCPT ); Mon, 1 Mar 2021 15:27:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:45780 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242980AbhCAUVN (ORCPT ); Mon, 1 Mar 2021 15:21:13 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id CA027653F7; Mon, 1 Mar 2021 18:04:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614621885; bh=xl0JcdjQOWgQaG+smQNz32yLrDoXo1nF7/FpfEsKmaA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tImNKuyd3Y+G18OzNa2C5PNlzTzonOfzh6sCEN86YdRhC/1Iqc/TH2/AmN0dbFBe+ 3Dyaiz3gam+U77/xjgkZvxYV8Kq4Iv4CctDpgXyIQAdoaAPu1JDw5ww150Gws1Wv6P xSAIxqUYV304S9kGZ/AI/0uGY9x1Zva572L/ZCEw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Frederic Weisbecker , "Peter Zijlstra (Intel)" , Ingo Molnar Subject: [PATCH 5.11 679/775] entry: Explicitly flush pending rcuog wakeup before last rescheduling point Date: Mon, 1 Mar 2021 17:14:07 +0100 Message-Id: <20210301161234.938370886@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210301161201.679371205@linuxfoundation.org> References: <20210301161201.679371205@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Frederic Weisbecker commit 47b8ff194c1fd73d58dc339b597d466fe48c8958 upstream. Following the idle loop model, cleanly check for pending rcuog wakeup before the last rescheduling point on resuming to user mode. This way we can avoid to do it from rcu_user_enter() with the last resort self-IPI hack that enforces rescheduling. Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20210131230548.32970-5-frederic@kernel.org Signed-off-by: Greg Kroah-Hartman --- kernel/entry/common.c | 7 +++++++ kernel/rcu/tree.c | 12 +++++++----- 2 files changed, 14 insertions(+), 5 deletions(-) --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -184,6 +184,10 @@ static unsigned long exit_to_user_mode_l * enabled above. */ local_irq_disable_exit_to_user(); + + /* Check if any of the above work has queued a deferred wakeup */ + rcu_nocb_flush_deferred_wakeup(); + ti_work = READ_ONCE(current_thread_info()->flags); } @@ -197,6 +201,9 @@ static void exit_to_user_mode_prepare(st lockdep_assert_irqs_disabled(); + /* Flush pending rcuog wakeup before the last need_resched() check */ + rcu_nocb_flush_deferred_wakeup(); + if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK)) ti_work = exit_to_user_mode_loop(regs, ti_work); --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -707,13 +707,15 @@ noinstr void rcu_user_enter(void) lockdep_assert_irqs_disabled(); /* - * We may be past the last rescheduling opportunity in the entry code. - * Trigger a self IPI that will fire and reschedule once we resume to - * user/guest mode. + * Other than generic entry implementation, we may be past the last + * rescheduling opportunity in the entry code. Trigger a self IPI + * that will fire and reschedule once we resume in user/guest mode. */ instrumentation_begin(); - if (do_nocb_deferred_wakeup(rdp) && need_resched()) - irq_work_queue(this_cpu_ptr(&late_wakeup_work)); + if (!IS_ENABLED(CONFIG_GENERIC_ENTRY) || (current->flags & PF_VCPU)) { + if (do_nocb_deferred_wakeup(rdp) && need_resched()) + irq_work_queue(this_cpu_ptr(&late_wakeup_work)); + } instrumentation_end(); rcu_eqs_enter(true);