From nobody Tue Sep 9 22:08:36 2025 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 33A4DC77B60 for ; Mon, 27 Mar 2023 20:25:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230210AbjC0UZR (ORCPT ); Mon, 27 Mar 2023 16:25:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54556 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229595AbjC0UZN (ORCPT ); Mon, 27 Mar 2023 16:25:13 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D391835BD for ; Mon, 27 Mar 2023 13:24:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1679948666; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Mu5ZzyYWSATBkbI4LlJA6D+0Mmfphw3RYNk8lrITOdU=; b=ZhbRkPnwLVzZfAqiSZ2OGAEZBygvWh4oPc0ylEpwEeTcSM+N6AtiexpMJSY8JObg3WrPiv RnbDssdPChiexyyFOhl/OQAh9lN0sIXHfbQwzQhg4bFJ0koFX9rke802pWS47zDF86mhWg c45I3n0ZKUPyiX37eAoZT3iK1QLCg7E= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-596-N9bmmKYXPvKrIs6WEbuAqA-1; Mon, 27 Mar 2023 16:24:24 -0400 X-MC-Unique: N9bmmKYXPvKrIs6WEbuAqA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 35075280BF61; Mon, 27 Mar 2023 20:24:24 +0000 (UTC) Received: from llong.com (unknown [10.22.17.245]) by smtp.corp.redhat.com (Postfix) with ESMTP id ED6652027040; Mon, 27 Mar 2023 20:24:23 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng Cc: linux-kernel@vger.kernel.org Subject: [PATCH v2 5/8] locking/rwsem: Split out rwsem_reader_wake() Date: Mon, 27 Mar 2023 16:24:10 -0400 Message-Id: <20230327202413.1955856-6-longman@redhat.com> In-Reply-To: <20230327202413.1955856-1-longman@redhat.com> References: <20230327202413.1955856-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Peter Zijlstra To provide symmetry with rwsem_writer_wake(). Signed-off-by: Peter Zijlstra (Intel) --- kernel/locking/rwsem.c | 83 +++++++++++++++++++++++------------------- 1 file changed, 46 insertions(+), 37 deletions(-) diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 225e86326ea4..0bc262dc77fd 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -106,9 +106,9 @@ * atomic_long_cmpxchg() will be used to obtain writer lock. * * There are three places where the lock handoff bit may be set or cleared. - * 1) rwsem_mark_wake() for readers -- set, clear + * 1) rwsem_reader_wake() for readers -- set, clear * 2) rwsem_try_write_lock() for writers -- set, clear - * 3) rwsem_del_waiter() -- clear + * 3) rwsem_del_waiter() -- clear * * For all the above cases, wait_lock will be held. A writer must also * be the first one in the wait_list to be eligible for setting the handoff @@ -377,7 +377,7 @@ rwsem_add_waiter(struct rw_semaphore *sem, struct rwsem= _waiter *waiter) /* * Remove a waiter from the wait_list and clear flags. * - * Both rwsem_mark_wake() and rwsem_try_write_lock() contain a full 'copy'= of + * Both rwsem_reader_wake() and rwsem_try_write_lock() contain a full 'cop= y' of * this function. Modify with care. * * Return: true if wait_list isn't empty and false otherwise @@ -483,42 +483,15 @@ static void rwsem_writer_wake(struct rw_semaphore *se= m, rwsem_waiter_wake(waiter, wake_q); } =20 -/* - * handle the lock release when processes blocked on it that can now run - * - if we come here from up_xxxx(), then the RWSEM_FLAG_WAITERS bit must - * have been set. - * - there must be someone on the queue - * - the wait_lock must be held by the caller - * - tasks are marked for wakeup, the caller must later invoke wake_up_q() - * to actually wakeup the blocked task(s) and drop the reference count, - * preferably when the wait_lock is released - * - woken process blocks are discarded from the list after having task ze= roed - * - writers are only marked woken if downgrading is false - * - * Implies rwsem_del_waiter() for all woken readers. - */ -static void rwsem_mark_wake(struct rw_semaphore *sem, - enum rwsem_wake_type wake_type, - struct wake_q_head *wake_q) +static void rwsem_reader_wake(struct rw_semaphore *sem, + enum rwsem_wake_type wake_type, + struct rwsem_waiter *waiter, + struct wake_q_head *wake_q) { - struct rwsem_waiter *waiter, *tmp; long count, woken =3D 0, adjustment =3D 0; + struct rwsem_waiter *tmp; struct list_head wlist; =20 - lockdep_assert_held(&sem->wait_lock); - - /* - * Take a peek at the queue head waiter such that we can determine - * the wakeup(s) to perform. - */ - waiter =3D rwsem_first_waiter(sem); - - if (waiter->type =3D=3D RWSEM_WAITING_FOR_WRITE) { - if (wake_type =3D=3D RWSEM_WAKE_ANY) - rwsem_writer_wake(sem, waiter, wake_q); - return; - } - /* * No reader wakeup if there are too many of them already. */ @@ -634,6 +607,42 @@ static void rwsem_mark_wake(struct rw_semaphore *sem, rwsem_waiter_wake(waiter, wake_q); } =20 +/* + * handle the lock release when processes blocked on it that can now run + * - if we come here from up_xxxx(), then the RWSEM_FLAG_WAITERS bit must + * have been set. + * - there must be someone on the queue + * - the wait_lock must be held by the caller + * - tasks are marked for wakeup, the caller must later invoke wake_up_q() + * to actually wakeup the blocked task(s) and drop the reference count, + * preferably when the wait_lock is released + * - woken process blocks are discarded from the list after having task ze= roed + * - writers are only marked woken if downgrading is false + * + * Implies rwsem_del_waiter() for all woken waiters. + */ +static void rwsem_mark_wake(struct rw_semaphore *sem, + enum rwsem_wake_type wake_type, + struct wake_q_head *wake_q) +{ + struct rwsem_waiter *waiter; + + lockdep_assert_held(&sem->wait_lock); + + /* + * Take a peek at the queue head waiter such that we can determine + * the wakeup(s) to perform. + */ + waiter =3D rwsem_first_waiter(sem); + + if (waiter->type =3D=3D RWSEM_WAITING_FOR_WRITE) { + if (wake_type =3D=3D RWSEM_WAKE_ANY) + rwsem_writer_wake(sem, waiter, wake_q); + } else { + rwsem_reader_wake(sem, wake_type, waiter, wake_q); + } +} + /* * Remove a waiter and try to wake up other waiters in the wait queue * This function is called from the out_nolock path of both the reader and @@ -1022,8 +1031,8 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, lo= ng count, unsigned int stat if ((rcnt =3D=3D 1) && (count & RWSEM_FLAG_WAITERS)) { raw_spin_lock_irq(&sem->wait_lock); if (!list_empty(&sem->wait_list)) - rwsem_mark_wake(sem, RWSEM_WAKE_READ_OWNED, - &wake_q); + rwsem_mark_wake(sem, RWSEM_WAKE_READ_OWNED, &wake_q); + raw_spin_unlock_irq(&sem->wait_lock); wake_up_q(&wake_q); } --=20 2.31.1