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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 BEDFEC2D0E4 for ; Wed, 18 Nov 2020 03:05:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 78E9824180 for ; Wed, 18 Nov 2020 03:05:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hzZzN7bZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727166AbgKRDFG (ORCPT ); Tue, 17 Nov 2020 22:05:06 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:47321 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726342AbgKRDFF (ORCPT ); Tue, 17 Nov 2020 22:05:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605668703; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:in-reply-to:in-reply-to:references:references; bh=Km5uaO7gRr1nPX+/XjbMGoi2DLABbzIXF5OZYikrBXo=; b=hzZzN7bZ206OIWNWpGulnp2TKM5QD1Q7XbDK85toE9nEFyg5bwUB90uxu4RSfI/qmBYEfN fyPR9/gY0nSZKGQNnmjnMw9Z0PErG+7lDgkn3nb44KySsoRP5LWOTgIoOn/xD7vZGB4VMC dLj+AaYbwJoGcMo19guAwYtjlocXJ1Q= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-103-j0I_OfEvOfOV-C0ZR6uRYw-1; Tue, 17 Nov 2020 22:05:01 -0500 X-MC-Unique: j0I_OfEvOfOV-C0ZR6uRYw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 92C501084D64; Wed, 18 Nov 2020 03:05:00 +0000 (UTC) Received: from llong.com (ovpn-113-17.rdu2.redhat.com [10.10.113.17]) by smtp.corp.redhat.com (Postfix) with ESMTP id D94025C1A3; Wed, 18 Nov 2020 03:04:59 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Ingo Molnar , Will Deacon Cc: linux-kernel@vger.kernel.org, Davidlohr Bueso , Phil Auld , Waiman Long Subject: [PATCH 1/5] locking/rwsem: Pass the current atomic count to rwsem_down_read_slowpath() Date: Tue, 17 Nov 2020 22:04:25 -0500 Message-Id: <20201118030429.23017-2-longman@redhat.com> In-Reply-To: <20201118030429.23017-1-longman@redhat.com> References: <20201118030429.23017-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The atomic count value right after reader count increment can be useful to determine the rwsem state at trylock time. So the count value is passed down to rwsem_down_read_slowpath() to be used when appropriate. Signed-off-by: Waiman Long --- kernel/locking/rwsem.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index f11b9bd3431d..12761e02ab9b 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -270,12 +270,12 @@ static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem) owner | RWSEM_NONSPINNABLE)); } -static inline bool rwsem_read_trylock(struct rw_semaphore *sem) +static inline long rwsem_read_trylock(struct rw_semaphore *sem) { long cnt = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count); if (WARN_ON_ONCE(cnt < 0)) rwsem_set_nonspinnable(sem); - return !(cnt & RWSEM_READ_FAILED_MASK); + return cnt; } /* @@ -989,9 +989,9 @@ rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable) * Wait for the read lock to be granted */ static struct rw_semaphore __sched * -rwsem_down_read_slowpath(struct rw_semaphore *sem, int state) +rwsem_down_read_slowpath(struct rw_semaphore *sem, int state, long count) { - long count, adjustment = -RWSEM_READER_BIAS; + long adjustment = -RWSEM_READER_BIAS; struct rwsem_waiter waiter; DEFINE_WAKE_Q(wake_q); bool wake = false; @@ -1337,8 +1337,10 @@ static struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem) */ static inline void __down_read(struct rw_semaphore *sem) { - if (!rwsem_read_trylock(sem)) { - rwsem_down_read_slowpath(sem, TASK_UNINTERRUPTIBLE); + long count = rwsem_read_trylock(sem); + + if (count & RWSEM_READ_FAILED_MASK) { + rwsem_down_read_slowpath(sem, TASK_UNINTERRUPTIBLE, count); DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem); } else { rwsem_set_reader_owned(sem); @@ -1347,8 +1349,10 @@ static inline void __down_read(struct rw_semaphore *sem) static inline int __down_read_killable(struct rw_semaphore *sem) { - if (!rwsem_read_trylock(sem)) { - if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_KILLABLE))) + long count = rwsem_read_trylock(sem); + + if (count & RWSEM_READ_FAILED_MASK) { + if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_KILLABLE, count))) return -EINTR; DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem); } else { -- 2.18.1