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 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 1CC2CC433DB for ; Mon, 15 Feb 2021 14:59:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D43AE64EB3 for ; Mon, 15 Feb 2021 14:59:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230314AbhBOO73 (ORCPT ); Mon, 15 Feb 2021 09:59:29 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:33152 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230098AbhBOO41 (ORCPT ); Mon, 15 Feb 2021 09:56:27 -0500 Date: Mon, 15 Feb 2021 14:55:44 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1613400945; 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; bh=TAkZBzhKHn6dqov3kRFxkwM0y9BMHSkNDXC2UtFtqXY=; b=fTDEX4pZBntwSSEFEFQu6NKbRrLIKluPJvThDHtLROS51FG8UFn1vqUP22OQCrsXgaNOmc 9iJtGBbRWyhNCREkE4SCxoYDHFdF5vPXNuG6HGF4hR0zCAc1D6abHNQuBUJBP15xLOlQwC HU8g6q8iipQkf7yUasHMhPKQCUSzpkf78xF7ZLbldcjfDIYMhThULLMdXNkYa1hFThadn/ aeReRhFDm8EWiddV9bsf2w0Ae8P2gTnvUN6ZwUyfpnKRdvzor5puad8YGd6M+D2CTVN78M YduCleh7pWSCUbokEJE6X7VZeHNv4JDU4pnQK9XCerQdz6OnSw1HEMiRXwoTzA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1613400945; 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; bh=TAkZBzhKHn6dqov3kRFxkwM0y9BMHSkNDXC2UtFtqXY=; b=8UwjhCDIApQlaNIMom1DOYbGd9gwFj+1eTSfu8Jj/1Wb5rnGc4HOGDaUDQj8R8r6lU2pNL +hExSUQJJZ+n/vAQ== From: "tip-bot2 for Paul E. McKenney" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: core/rcu] srcu: Provide internal interface to start a Tree SRCU grace period Cc: Kent Overstreet , Neeraj Upadhyay , "Paul E. McKenney" , x86@kernel.org, linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-ID: <161340094498.20312.1445677559215645808.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 core/rcu branch of tip: Commit-ID: 29d2bb94a8a126ce80ffbb433b648b32fdea524e Gitweb: https://git.kernel.org/tip/29d2bb94a8a126ce80ffbb433b648b32fdea524e Author: Paul E. McKenney AuthorDate: Fri, 13 Nov 2020 10:08:09 -08:00 Committer: Paul E. McKenney CommitterDate: Mon, 04 Jan 2021 13:53:37 -08:00 srcu: Provide internal interface to start a Tree SRCU grace period There is a need for a polling interface for SRCU grace periods. This polling needs to initiate an SRCU grace period without having to queue (and manage) a callback. This commit therefore splits the Tree SRCU __call_srcu() function into callback-initialization and queuing/start-grace-period portions, with the latter in a new function named srcu_gp_start_if_needed(). This function may be passed a NULL callback pointer, in which case it will refrain from queuing anything. Why have the new function mess with queuing? Locking considerations, of course! Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/ Reported-by: Kent Overstreet Reviewed-by: Neeraj Upadhyay Signed-off-by: Paul E. McKenney --- kernel/rcu/srcutree.c | 66 +++++++++++++++++++++++------------------- 1 file changed, 37 insertions(+), 29 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 0f23d20..9a7b650 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -808,6 +808,42 @@ static void srcu_leak_callback(struct rcu_head *rhp) } /* + * Start an SRCU grace period, and also queue the callback if non-NULL. + */ +static void srcu_gp_start_if_needed(struct srcu_struct *ssp, struct rcu_head *rhp, bool do_norm) +{ + unsigned long flags; + int idx; + bool needexp = false; + bool needgp = false; + unsigned long s; + struct srcu_data *sdp; + + idx = srcu_read_lock(ssp); + sdp = raw_cpu_ptr(ssp->sda); + spin_lock_irqsave_rcu_node(sdp, flags); + rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp); + rcu_segcblist_advance(&sdp->srcu_cblist, + rcu_seq_current(&ssp->srcu_gp_seq)); + s = rcu_seq_snap(&ssp->srcu_gp_seq); + (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, s); + if (ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s)) { + sdp->srcu_gp_seq_needed = s; + needgp = true; + } + if (!do_norm && ULONG_CMP_LT(sdp->srcu_gp_seq_needed_exp, s)) { + sdp->srcu_gp_seq_needed_exp = s; + needexp = true; + } + spin_unlock_irqrestore_rcu_node(sdp, flags); + if (needgp) + srcu_funnel_gp_start(ssp, sdp, s, do_norm); + else if (needexp) + srcu_funnel_exp_start(ssp, sdp->mynode, s); + srcu_read_unlock(ssp, idx); +} + +/* * Enqueue an SRCU callback on the srcu_data structure associated with * the current CPU and the specified srcu_struct structure, initiating * grace-period processing if it is not already running. @@ -838,13 +874,6 @@ static void srcu_leak_callback(struct rcu_head *rhp) static void __call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp, rcu_callback_t func, bool do_norm) { - unsigned long flags; - int idx; - bool needexp = false; - bool needgp = false; - unsigned long s; - struct srcu_data *sdp; - check_init_srcu_struct(ssp); if (debug_rcu_head_queue(rhp)) { /* Probable double call_srcu(), so leak the callback. */ @@ -853,28 +882,7 @@ static void __call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp, return; } rhp->func = func; - idx = srcu_read_lock(ssp); - sdp = raw_cpu_ptr(ssp->sda); - spin_lock_irqsave_rcu_node(sdp, flags); - rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp); - rcu_segcblist_advance(&sdp->srcu_cblist, - rcu_seq_current(&ssp->srcu_gp_seq)); - s = rcu_seq_snap(&ssp->srcu_gp_seq); - (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, s); - if (ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s)) { - sdp->srcu_gp_seq_needed = s; - needgp = true; - } - if (!do_norm && ULONG_CMP_LT(sdp->srcu_gp_seq_needed_exp, s)) { - sdp->srcu_gp_seq_needed_exp = s; - needexp = true; - } - spin_unlock_irqrestore_rcu_node(sdp, flags); - if (needgp) - srcu_funnel_gp_start(ssp, sdp, s, do_norm); - else if (needexp) - srcu_funnel_exp_start(ssp, sdp->mynode, s); - srcu_read_unlock(ssp, idx); + srcu_gp_start_if_needed(ssp, rhp, do_norm); } /**