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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 9BCA8C43603 for ; Tue, 10 Dec 2019 04:02:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7063C2077B for ; Tue, 10 Dec 2019 04:02:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575950523; bh=m2GXoSyuxJbV9GL011u2OK+TshJgf3LR/XQ5uYfnR1Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=OYxL7siMpPp1pxL/JPIpPBgA0w/E8zlSSBhPCar3nDo/5osTvZ9Wqrs9H0BCHSbRa Aq/xsF1gjn3J9lnybEJen5LKW+aSDTZlx9DDkQRbApPm/vczubX0nNpRZUSSbUahi2 H7FKNozTCjK4GhvXQySmY55mGmyvN1+1XvZfZvJM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727053AbfLJECC (ORCPT ); Mon, 9 Dec 2019 23:02:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:41676 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726989AbfLJECC (ORCPT ); Mon, 9 Dec 2019 23:02:02 -0500 Received: from paulmck-ThinkPad-P72.home (199-192-87-166.static.wiline.com [199.192.87.166]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A88DB214D8; Tue, 10 Dec 2019 04:02:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575950521; bh=m2GXoSyuxJbV9GL011u2OK+TshJgf3LR/XQ5uYfnR1Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Kc/tq1xbJEGaYDK4dsApB34Mss7gP2wVa0IoPZ37YBEHSnL9q75BVdCJdPXH26UTK IqSVkU2/iuxDqAfIzmav4rv7ynSsFEvpRnKL/LEXCxI1k6endaK9M0jqVxEq463UXY VZa1cXLgRDW7QTsPS0X1b5kEBc5SPZ/wbT33gUx8= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 08/10] rcu: Update tree_exp.h function-header comments Date: Mon, 9 Dec 2019 20:01:52 -0800 Message-Id: <20191210040154.2498-8-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20191210040122.GA2419@paulmck-ThinkPad-P72> References: <20191210040122.GA2419@paulmck-ThinkPad-P72> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: "Paul E. McKenney" The function-header comments in kernel/rcu/tree_exp.h have gotten a bit out of date, so this commit updates a number of them. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_exp.h | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 3923c07..1eafbcd 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -21,7 +21,7 @@ static void rcu_exp_gp_seq_start(void) } /* - * Return then value that expedited-grace-period counter will have + * Return the value that the expedited-grace-period counter will have * at the end of the current grace period. */ static __maybe_unused unsigned long rcu_exp_gp_seq_endval(void) @@ -39,7 +39,9 @@ static void rcu_exp_gp_seq_end(void) } /* - * Take a snapshot of the expedited-grace-period counter. + * Take a snapshot of the expedited-grace-period counter, which is the + * earliest value that will indicate that a full grace period has + * elapsed since the current time. */ static unsigned long rcu_exp_gp_seq_snap(void) { @@ -143,22 +145,18 @@ static void __maybe_unused sync_exp_reset_tree(void) * Return non-zero if there is no RCU expedited grace period in progress * for the specified rcu_node structure, in other words, if all CPUs and * tasks covered by the specified rcu_node structure have done their bit - * for the current expedited grace period. Works only for preemptible - * RCU -- other RCU implementation use other means. - * - * Caller must hold the specificed rcu_node structure's ->lock + * for the current expedited grace period. */ static bool sync_rcu_exp_done(struct rcu_node *rnp) { raw_lockdep_assert_held_rcu_node(rnp); - return rnp->exp_tasks == NULL && READ_ONCE(rnp->expmask) == 0; } /* - * Like sync_rcu_exp_done(), but this function assumes the caller doesn't - * hold the rcu_node's ->lock, and will acquire and release the lock itself + * Like sync_rcu_exp_done(), but where the caller does not hold the + * rcu_node's ->lock. */ static bool sync_rcu_exp_done_unlocked(struct rcu_node *rnp) { @@ -180,8 +178,6 @@ static bool sync_rcu_exp_done_unlocked(struct rcu_node *rnp) * which the task was queued or to one of that rcu_node structure's ancestors, * recursively up the tree. (Calm down, calm down, we do the recursion * iteratively!) - * - * Caller must hold the specified rcu_node structure's ->lock. */ static void __rcu_report_exp_rnp(struct rcu_node *rnp, bool wake, unsigned long flags) @@ -189,6 +185,7 @@ static void __rcu_report_exp_rnp(struct rcu_node *rnp, { unsigned long mask; + raw_lockdep_assert_held_rcu_node(rnp); for (;;) { if (!sync_rcu_exp_done(rnp)) { if (!rnp->expmask) @@ -452,6 +449,10 @@ static void sync_rcu_exp_select_cpus(void) flush_work(&rnp->rew.rew_work); } +/* + * Wait for the expedited grace period to elapse, issuing any needed + * RCU CPU stall warnings along the way. + */ static void synchronize_sched_expedited_wait(void) { int cpu; @@ -781,7 +782,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp) * implementations, it is still unfriendly to real-time workloads, so is * thus not recommended for any sort of common-case code. In fact, if * you are using synchronize_rcu_expedited() in a loop, please restructure - * your code to batch your updates, and then Use a single synchronize_rcu() + * your code to batch your updates, and then use a single synchronize_rcu() * instead. * * This has the same semantics as (but is more brutal than) synchronize_rcu(). -- 2.9.5