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=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 EE79DC352A3 for ; Tue, 11 Feb 2020 12:48:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA96824676 for ; Tue, 11 Feb 2020 12:48:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729033AbgBKMsa (ORCPT ); Tue, 11 Feb 2020 07:48:30 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:46085 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729003AbgBKMs2 (ORCPT ); Tue, 11 Feb 2020 07:48:28 -0500 Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1j1Uxj-0007lb-Pl; Tue, 11 Feb 2020 13:48:23 +0100 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 741841C2017; Tue, 11 Feb 2020 13:48:23 +0100 (CET) Date: Tue, 11 Feb 2020 12:48:23 -0000 From: "tip-bot2 for Peter Zijlstra" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: locking/core] locking/percpu-rwsem: Extract __percpu_down_read_trylock() Cc: "Peter Zijlstra (Intel)" , Ingo Molnar , Davidlohr Bueso , Will Deacon , Waiman Long , Juri Lelli , x86 , LKML In-Reply-To: <20200131151540.098485539@infradead.org> References: <20200131151540.098485539@infradead.org> MIME-Version: 1.0 Message-ID: <158142530316.411.8935420422825778955.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the locking/core branch of tip: Commit-ID: 75ff64572e497578e238fefbdff221c96f29067a Gitweb: https://git.kernel.org/tip/75ff64572e497578e238fefbdff221c96f29067a Author: Peter Zijlstra AuthorDate: Thu, 31 Oct 2019 12:34:23 +01:00 Committer: Ingo Molnar CommitterDate: Tue, 11 Feb 2020 13:10:55 +01:00 locking/percpu-rwsem: Extract __percpu_down_read_trylock() In preparation for removing the embedded rwsem and building a custom lock, extract the read-trylock primitive. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Davidlohr Bueso Acked-by: Will Deacon Acked-by: Waiman Long Tested-by: Juri Lelli Link: https://lkml.kernel.org/r/20200131151540.098485539@infradead.org --- kernel/locking/percpu-rwsem.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index becf925..b155e8e 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -45,7 +45,7 @@ void percpu_free_rwsem(struct percpu_rw_semaphore *sem) } EXPORT_SYMBOL_GPL(percpu_free_rwsem); -bool __percpu_down_read(struct percpu_rw_semaphore *sem, bool try) +static bool __percpu_down_read_trylock(struct percpu_rw_semaphore *sem) { __this_cpu_inc(*sem->read_count); @@ -73,11 +73,18 @@ bool __percpu_down_read(struct percpu_rw_semaphore *sem, bool try) if (likely(!smp_load_acquire(&sem->readers_block))) return true; - /* - * Per the above comment; we still have preemption disabled and - * will thus decrement on the same CPU as we incremented. - */ - __percpu_up_read(sem); + __this_cpu_dec(*sem->read_count); + + /* Prod writer to re-evaluate readers_active_check() */ + rcuwait_wake_up(&sem->writer); + + return false; +} + +bool __percpu_down_read(struct percpu_rw_semaphore *sem, bool try) +{ + if (__percpu_down_read_trylock(sem)) + return true; if (try) return false;