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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21049C433EF for ; Wed, 29 Sep 2021 22:10:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0430260FC2 for ; Wed, 29 Sep 2021 22:10:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347220AbhI2WMV (ORCPT ); Wed, 29 Sep 2021 18:12:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:60842 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347214AbhI2WMQ (ORCPT ); Wed, 29 Sep 2021 18:12:16 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id F0F6D61423; Wed, 29 Sep 2021 22:10:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1632953435; bh=DBWs3V0sa4GChCABC3MuvhuPRpOsaCGotPLqeHtOz8s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O+MXbULhCLx+ghC+3HJI03IlziVsmR3t4kshPrmZ5vCuJ6TAVsxrU+Ly1f8PihJYV jJcQGyFVEzBzO7bZ1d1/jCbPT1FaaEBVF2Rp9cmLpoJf8KeJE6XVSxQx7xaE8HFVYS YqjJ+92fuFKH/YP5Cw03WsjDAQ1BbDqS5rGhXE/XQTuQcBnQs0wcPHzjlZiyyzfy2v dOtXwVQeXkIRqLwRU295/SmJ9eNEGXyhf56Ps9PMK3At9F0cv92ZwQNYFapUW4sHtF 2LAfm29AT9PgaB4LQY5fE8+x6C6U6K5kppw3UtyolSkDG55DvQzN92hhqVyorTaoGu keQ4Z3L07evwA== From: Frederic Weisbecker To: "Paul E . McKenney" Cc: LKML , Frederic Weisbecker , Sebastian Andrzej Siewior , Peter Zijlstra , Uladzislau Rezki , Valentin Schneider , Thomas Gleixner , Boqun Feng , Neeraj Upadhyay , Josh Triplett , Joel Fernandes , rcu@vger.kernel.org Subject: [RFC PATCH 06/11] rcu/nocb: Check a stable offloaded state to manipulate qlen_last_fqs_check Date: Thu, 30 Sep 2021 00:10:07 +0200 Message-Id: <20210929221012.228270-7-frederic@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210929221012.228270-1-frederic@kernel.org> References: <20210929221012.228270-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It's unclear why rdp->qlen_last_fqs_check is updated only on offloaded rdp. Also rcu_core() and NOCB kthreads can run concurrently, should we do the update on both cases? Probably not because one can erase the initialized value of the other. For now shutdown the RT warning due to volatile offloading state check and wait for a debate after this half-baked patch. Reported-by: Valentin Schneider Signed-off-by: Frederic Weisbecker Cc: Valentin Schneider Cc: Peter Zijlstra Cc: Sebastian Andrzej Siewior Cc: Josh Triplett Cc: Joel Fernandes Cc: Boqun Feng Cc: Neeraj Upadhyay Cc: Uladzislau Rezki Cc: Thomas Gleixner --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 73971b8024d8..b1fc6e498d90 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2508,7 +2508,7 @@ static void rcu_do_batch(struct rcu_data *rdp) trace_rcu_batch_start(rcu_state.name, rcu_segcblist_n_cbs(&rdp->cblist), bl); rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl); - if (offloaded) + if (rcu_rdp_is_offloaded(rdp)) rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbDequeued")); -- 2.25.1