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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 A4262CA9ECF for ; Fri, 1 Nov 2019 18:31:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 77B4221734 for ; Fri, 1 Nov 2019 18:31:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727495AbfKASbj (ORCPT ); Fri, 1 Nov 2019 14:31:39 -0400 Received: from mx2.suse.de ([195.135.220.15]:43322 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727222AbfKASbj (ORCPT ); Fri, 1 Nov 2019 14:31:39 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 41AABB309; Fri, 1 Nov 2019 18:31:37 +0000 (UTC) From: Davidlohr Bueso To: eric@anholt.net, wahrenst@gmx.net Cc: gregkh@linuxfoundation.org, dave@stgolabs.net, linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org Subject: [PATCH resend] staging: vc04_services: replace g_free_fragments_mutex with spinlock Date: Fri, 1 Nov 2019 11:29:49 -0700 Message-Id: <20191101182949.21225-1-dave@stgolabs.net> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20191028165909.GA469472@kroah.com> References: <20191028165909.GA469472@kroah.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is no need to be using a semaphore, or a sleeping lock in the first place: critical region is extremely short, does not call into any blocking calls and furthermore lock and unlocking operations occur in the same context. Get rid of another semaphore user by replacing it with a spinlock. Signed-off-by: Davidlohr Bueso --- This is in an effort to further reduce semaphore users in the kernel. This is a resend, which just seems simpler given the confusions. .../staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c index 8dc730cfe7a6..710d21654128 100644 --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c @@ -63,7 +63,7 @@ static char *g_free_fragments; static struct semaphore g_free_fragments_sema; static struct device *g_dev; -static DEFINE_SEMAPHORE(g_free_fragments_mutex); +static DEFINE_SPINLOCK(g_free_fragments_lock); static irqreturn_t vchiq_doorbell_irq(int irq, void *dev_id); @@ -528,11 +528,11 @@ create_pagelist(char __user *buf, size_t count, unsigned short type) WARN_ON(g_free_fragments == NULL); - down(&g_free_fragments_mutex); + spin_lock(&g_free_fragments_lock); fragments = g_free_fragments; WARN_ON(fragments == NULL); g_free_fragments = *(char **) g_free_fragments; - up(&g_free_fragments_mutex); + spin_unlock(&g_free_fragments_lock); pagelist->type = PAGELIST_READ_WITH_FRAGMENTS + (fragments - g_fragments_base) / g_fragments_size; } @@ -591,10 +591,10 @@ free_pagelist(struct vchiq_pagelist_info *pagelistinfo, kunmap(pages[num_pages - 1]); } - down(&g_free_fragments_mutex); + spin_lock(&g_free_fragments_lock); *(char **)fragments = g_free_fragments; g_free_fragments = fragments; - up(&g_free_fragments_mutex); + spin_unlock(&g_free_fragments_lock); up(&g_free_fragments_sema); } -- 2.16.4