Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756128Ab0FSOq2 (ORCPT ); Sat, 19 Jun 2010 10:46:28 -0400 Received: from arkanian.console-pimps.org ([212.110.184.194]:53190 "EHLO arkanian.console-pimps.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756081Ab0FSOq1 (ORCPT ); Sat, 19 Jun 2010 10:46:27 -0400 From: Matt Fleming To: Lars-Peter Clausen Cc: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, Lars-Peter Clausen , Andrew Morton , linux-mmc@vger.kernel.org, Ralf Baechle Subject: Re: [PATCH v2 18/26] MMC: Add JZ4740 mmc driver In-Reply-To: <1276924111-11158-19-git-send-email-lars@metafoo.de> References: <1276924111-11158-1-git-send-email-lars@metafoo.de> <1276924111-11158-19-git-send-email-lars@metafoo.de> User-Agent: Notmuch/0.3.1-61-g3f63bb6 (http://notmuchmail.org) Emacs/23.1.90.2 (x86_64-unknown-linux-gnu) Date: Sat, 19 Jun 2010 15:46:25 +0100 Message-ID: <87ocf7ozb2.fsf@linux-g6p1.site> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1862 Lines: 60 On Sat, 19 Jun 2010 07:08:23 +0200, Lars-Peter Clausen wrote: > This patch adds support for the mmc controller on JZ4740 SoCs. > Hey Lars-Peter, I had a quick look over this patch and it looks OK. Just a few comments. > +static void jz4740_mmc_timeout(unsigned long data) > +{ > + struct jz4740_mmc_host *host = (struct jz4740_mmc_host *)data; > + unsigned long flags; > + > + spin_lock_irqsave(&host->lock, flags); > + if (!host->waiting) { > + spin_unlock_irqrestore(&host->lock, flags); > + return; > + } > + > + host->waiting = 0; > + > + spin_unlock_irqrestore(&host->lock, flags); > + > + host->req->cmd->error = -ETIMEDOUT; > + jz4740_mmc_request_done(host); > +} > + Taking a spinlock and disabling interrupts seems like too much overhead to simply test and clear a bit. Wouldn't it be better to implement this with test_and_clear_bit(), which on MIPS will likely be implemented with ll/sc instructions? It's particularly important to keep this low-overhead since this bit is modified in the interrupt handler. > +static void jz4740_mmc_request_done(struct jz4740_mmc_host *host) > +{ > + struct mmc_request *req; > + unsigned long flags; > + > + spin_lock_irqsave(&host->lock, flags); > + req = host->req; > + host->req = NULL; > + host->waiting = 0; > + spin_unlock_irqrestore(&host->lock, flags); > + > + if (!unlikely(req)) > + return; > + > + mmc_request_done(host->mmc, req); > +} > + Am I right in thinking that this spinlock guards against the interrupt handler and the timeout function running at the same time? So it's not really possible to drop the spinlock from here? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/