From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Herrmann Subject: [PATCH RFC 2/4] backlight: use spin-lock to protect device list Date: Wed, 10 Sep 2014 17:54:21 +0200 Message-ID: <1410364463-12692-3-git-send-email-dh.herrmann@gmail.com> References: <1410364463-12692-1-git-send-email-dh.herrmann@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wi0-f179.google.com (mail-wi0-f179.google.com [209.85.212.179]) by gabe.freedesktop.org (Postfix) with ESMTP id C539F89FDE for ; Wed, 10 Sep 2014 08:54:55 -0700 (PDT) Received: by mail-wi0-f179.google.com with SMTP id q5so6559211wiv.0 for ; Wed, 10 Sep 2014 08:54:55 -0700 (PDT) In-Reply-To: <1410364463-12692-1-git-send-email-dh.herrmann@gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: dri-devel@lists.freedesktop.org Cc: Matthew Garrett , Daniel Vetter , Bryan Wu , linux-kernel@vger.kernel.org, Lee Jones List-Id: dri-devel@lists.freedesktop.org There is really no reason to use a mutex to protect a simple list. Convert the list-lock to a simple spinlock instead. The spin-locks prepare for a backlight_find() helper, which should preferably be usable from atomic context. A mutex would prevent that, so use an irq-save spinlock instead. Signed-off-by: David Herrmann --- drivers/video/backlight/backlight.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 726c6c6..33b64be 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -16,13 +16,14 @@ #include #include #include +#include #ifdef CONFIG_PMAC_BACKLIGHT #include #endif static LIST_HEAD(backlight_dev_list); -static DEFINE_MUTEX(backlight_dev_list_mutex); +static DEFINE_SPINLOCK(backlight_dev_list_lock); static BLOCKING_NOTIFIER_HEAD(backlight_notifier); static const char *const backlight_types[] = { @@ -369,9 +370,9 @@ struct backlight_device *backlight_device_register(const char *name, mutex_unlock(&pmac_backlight_mutex); #endif - mutex_lock(&backlight_dev_list_mutex); + spin_lock_irq(&backlight_dev_list_lock); list_add(&new_bd->entry, &backlight_dev_list); - mutex_unlock(&backlight_dev_list_mutex); + spin_unlock_irq(&backlight_dev_list_lock); blocking_notifier_call_chain(&backlight_notifier, BACKLIGHT_REGISTERED, new_bd); @@ -384,15 +385,16 @@ bool backlight_device_registered(enum backlight_type type) { bool found = false; struct backlight_device *bd; + unsigned long flags; - mutex_lock(&backlight_dev_list_mutex); + spin_lock_irqsave(&backlight_dev_list_lock, flags); list_for_each_entry(bd, &backlight_dev_list, entry) { if (bd->props.type == type) { found = true; break; } } - mutex_unlock(&backlight_dev_list_mutex); + spin_unlock_irqrestore(&backlight_dev_list_lock, flags); return found; } @@ -409,9 +411,9 @@ void backlight_device_unregister(struct backlight_device *bd) if (!bd) return; - mutex_lock(&backlight_dev_list_mutex); + spin_lock_irq(&backlight_dev_list_lock); list_del(&bd->entry); - mutex_unlock(&backlight_dev_list_mutex); + spin_unlock_irq(&backlight_dev_list_lock); #ifdef CONFIG_PMAC_BACKLIGHT mutex_lock(&pmac_backlight_mutex); -- 2.1.0