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=unavailable 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 41953C47E49 for ; Fri, 1 Nov 2019 18:31:46 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1F2C520578 for ; Fri, 1 Nov 2019 18:31:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F2C520578 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=stgolabs.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=driverdev-devel-bounces@linuxdriverproject.org Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 1C77087E24; Fri, 1 Nov 2019 18:31:45 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id u3ZJRMJQS1jE; Fri, 1 Nov 2019 18:31:42 +0000 (UTC) Received: from ash.osuosl.org (ash.osuosl.org [140.211.166.34]) by whitealder.osuosl.org (Postfix) with ESMTP id 2F9B087DDF; Fri, 1 Nov 2019 18:31:42 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by ash.osuosl.org (Postfix) with ESMTP id 4D6F21BF33C for ; Fri, 1 Nov 2019 18:31:41 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 4A82286B66 for ; Fri, 1 Nov 2019 18:31:41 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id VLurBjE459LQ for ; Fri, 1 Nov 2019 18:31:40 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by fraxinus.osuosl.org (Postfix) with ESMTPS id 4B29386B54 for ; Fri, 1 Nov 2019 18:31:40 +0000 (UTC) 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 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> X-BeenThere: driverdev-devel@linuxdriverproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux Driver Project Developer List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devel@driverdev.osuosl.org, gregkh@linuxfoundation.org, dave@stgolabs.net, linux-kernel@vger.kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" 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 _______________________________________________ devel mailing list devel@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel