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=-9.7 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 6173CCA9EAF for ; Sun, 27 Oct 2019 22:18:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 39A2520659 for ; Sun, 27 Oct 2019 22:18:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727465AbfJ0WRH (ORCPT ); Sun, 27 Oct 2019 18:17:07 -0400 Received: from mx2.suse.de ([195.135.220.15]:50308 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726717AbfJ0WRH (ORCPT ); Sun, 27 Oct 2019 18:17:07 -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 C1DFFAD88; Sun, 27 Oct 2019 22:17:05 +0000 (UTC) From: Davidlohr Bueso To: eric@anholt.net, wahrenst@gmx.net Cc: gregkh@linuxfoundation.org, dave@stgolabs.net, linux-kernel@vger.kernel.org Subject: [PATCH] staging: vc04_services: replace g_free_fragments_mutex with spinlock Date: Sun, 27 Oct 2019 15:15:30 -0700 Message-Id: <20191027221530.12080-1-dave@stgolabs.net> X-Mailer: git-send-email 2.16.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There seems 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. .../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