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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C99E8C433F5 for ; Tue, 8 Mar 2022 18:04:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349363AbiCHSFc (ORCPT ); Tue, 8 Mar 2022 13:05:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41956 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231637AbiCHSFZ (ORCPT ); Tue, 8 Mar 2022 13:05:25 -0500 Received: from mail-lf1-x129.google.com (mail-lf1-x129.google.com [IPv6:2a00:1450:4864:20::129]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2EB735521D; Tue, 8 Mar 2022 10:04:28 -0800 (PST) Received: by mail-lf1-x129.google.com with SMTP id h14so8686110lfk.11; Tue, 08 Mar 2022 10:04:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=6SHxHLXJ2eYyw1tnxtVXf2yck6AofzgpVIfso9u7DAE=; b=YWxBm6Jx9v7Wlb2fdyVA4R/eCLykHIu5057o5yoxhiNe1ckeEcYcuoIlvL0CXgyUUS iCcHfjSkiUebD2r7d935yPKizxOzpol4fVwzGhe1sxB1SXtbSjuBLWqAfhVvXomhyf7V BnXT8+SGpjmpIZ/L55h1bxZ3H2uZjmLJz3IlPnl59Ufs7nykyUUz1vFD+GJdAuAbfX72 aDVKhnqFKkHplJiX2aOCMqJuGarphm3J7iBCGW4p41f350GRxKuiNvo8YaK6XmNTj1kT RwpAlAlpMgMInq7c/Fe45mxLaG95Ut4PwQ1pI+fqY/6Q5msR6vrqmQMsjGVAp/pbCwXr RpyA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=6SHxHLXJ2eYyw1tnxtVXf2yck6AofzgpVIfso9u7DAE=; b=lDBaT3/xIImb5z61/nNpvi8aXv8Y4u3xWma3Mru8rgRiKz8DwQQfWkHs/yqAl1RV2a ipNPpbtjG1/krBElTnAafrP3eB4DeV+5/Zi1PTFHkA2JOxNCLVt0iAX9pKEqSDetiyRx PMnWlXVpM4ycZr5jOfiJbz2m7hR6LFjjOthfyb7Od2CN8ZqSbKC+eNVdUtgL4S0KO8sT UlCMIhw5Feg8EHurBigsWQeHAO7Vad/mL9tdmGtQR0YwxD5bwbyIAx9hZ46KhY4LOiDn +14/7AAqm0WFUXSkHPeF2H/04tZxuFVSZeYpAWhGIr0wmpU9EQMPoJ/ep7THYb0e6WUZ GJbg== X-Gm-Message-State: AOAM530Om+IiySecn3ONSCXt1YrYXdYk5v8uqFSNjeiy6FeegCkvWXQH aeevQD85h6yZUjWmRk4Juxc= X-Google-Smtp-Source: ABdhPJzM/6dGiiSrzkwSlZG8G/sBalDM4RxDurXpIFsD9rt6m80xcXA4TbZGf9jQFZCFTRpLPDs6cA== X-Received: by 2002:a05:6512:3ca2:b0:445:98f6:40df with SMTP id h34-20020a0565123ca200b0044598f640dfmr11391467lfv.293.1646762664244; Tue, 08 Mar 2022 10:04:24 -0800 (PST) Received: from pc638.lan ([155.137.26.201]) by smtp.gmail.com with ESMTPSA id l11-20020a2e834b000000b00246308690e2sm3986488ljh.85.2022.03.08.10.04.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Mar 2022 10:04:23 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 8 Mar 2022 19:04:21 +0100 To: "Zhang, Qiang1" Cc: "Zhang, Qiang1" , paulmck@kernel.org, Neeraj Upadhyay , "frederic@kernel.org" , "linux-kernel@vger.kernel.org" , rcu@vger.kernel.org, bigeasy@linutronix.de Subject: Re: [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads Message-ID: References: <20220304092631.4123188-1-qiang1.zhang@intel.com> <81f69dd4-6ca9-760c-bec5-5cb27afbe788@quicinc.com> <20220307191512.GN4285@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220307191512.GN4285@paulmck-ThinkPad-P17-Gen-1> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Mon, Mar 07, 2022 at 02:03:17AM +0000, Zhang, Qiang1 wrote: > > On 3/4/2022 2:56 PM, Zqiang wrote: > > > When RCU_BOOST is enabled, the boost kthreads will boosting readers > > > who are blocking a given grace period, if the current reader tasks > > > have a higher priority than boost kthreads(the boost kthreads priority > > > not always 1, if the kthread_prio is set), boosting is useless, skip > > > current task and select next task to boosting, reduce the time for a > > > given grace period. > > > > > > Signed-off-by: Zqiang > > Adding to CC to get more eyes on this. I am not necessarily opposed to > it, but I don't do that much RT work myself these days. > > Thanx, Paul > > > > --- > > > kernel/rcu/tree_plugin.h | 10 +++++++++- > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > > > index c3d212bc5338..d35b6da66bbd 100644 > > > --- a/kernel/rcu/tree_plugin.h > > > +++ b/kernel/rcu/tree_plugin.h > > > @@ -12,6 +12,7 @@ > > > */ > > > > > > #include "../locking/rtmutex_common.h" > > > +#include > > > > > > static bool rcu_rdp_is_offloaded(struct rcu_data *rdp) > > > { > > > @@ -1065,13 +1066,20 @@ static int rcu_boost(struct rcu_node *rnp) > > > * section. > > > */ > > > t = container_of(tb, struct task_struct, rcu_node_entry); > > > + if (!rnp->exp_tasks && (dl_task(t) || t->prio <= current->prio)) { > > > + tb = rcu_next_node_entry(t, rnp); > > > + WRITE_ONCE(rnp->boost_tasks, tb); > > > + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > > > + goto end; > > > + } > > > + Why do you bypass the expedited grace period and boost any tasks anyway? Same way the expedited gp can be blocked by higher prior tasks SCHED_DEADLINE or SCHED_FIFO. Thanks! -- Vlad Rezki