linux-kernel - [PATCH 26/32] omap_hsmmc: prevent races with irq handler

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Date:	Fri, 10 Jul 2009 15:43:09 +0300
From:	Adrian Hunter <adrian.hunter@...ia.com>
To:	Pierre Ossman <pierre@...man.eu>
Cc:	Jarkko Lavinen <jarkko.lavinen@...ia.com>,
	Denis Karpov <ext-denis.2.karpov@...ia.com>,
	Adrian Hunter <adrian.hunter@...ia.com>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-omap Mailing List <linux-omap@...r.kernel.org>
Subject: [PATCH 26/32] omap_hsmmc: prevent races with irq handler

>From 242fae6293adec671b14354f215217354f5076a0 Mon Sep 17 00:00:00 2001
From: Adrian Hunter <adrian.hunter@...ia.com>
Date: Sat, 16 May 2009 10:32:34 +0300
Subject: [PATCH] omap_hsmmc: prevent races with irq handler

If an unexpected interrupt occurs while preparing the
next request, an oops can occur.

For example, a new request is setting up DMA for data
transfer so host->data is not NULL.  An unexpected
transfer complete (TC) interrupt comes along and
the interrupt handler sets host->data to NULL.  Oops!

Prevent that by disabling interrupts while setting up
a new request.

Signed-off-by: Adrian Hunter <adrian.hunter@...ia.com>
---
 drivers/mmc/host/omap_hsmmc.c |   16 ++++++++++++++++
 1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
index 28563d6..38e1410 100644
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c
@@ -452,6 +452,13 @@ mmc_omap_start_command(struct mmc_omap_host *host, struct mmc_command *cmd,
 	if (host->use_dma)
 		cmdreg |= DMA_EN;
 
+	/*
+	 * In an interrupt context (i.e. STOP command), the interrupt is already
+	 * enabled, otherwise it is not (i.e. new request).
+	 */
+	if (!in_interrupt())
+		enable_irq(host->irq);
+
 	OMAP_HSMMC_WRITE(host->base, ARG, cmd->arg);
 	OMAP_HSMMC_WRITE(host->base, CMD, cmdreg);
 }
@@ -1011,6 +1018,13 @@ static void omap_mmc_request(struct mmc_host *mmc, struct mmc_request *req)
 	struct mmc_omap_host *host = mmc_priv(mmc);
 	int err;
 
+	/*
+	 * Prevent races with the interrupt handler because of unexpected
+	 * interrupts, but not if we are already in interrupt context i.e.
+	 * retries.
+	 */
+	if (!in_interrupt())
+		disable_irq(host->irq);
 	WARN_ON(host->mrq != NULL);
 	host->mrq = req;
 	err = mmc_omap_prepare_data(host, req);
@@ -1019,6 +1033,8 @@ static void omap_mmc_request(struct mmc_host *mmc, struct mmc_request *req)
 		if (req->data)
 			req->data->error = err;
 		host->mrq = NULL;
+		if (!in_interrupt())
+			enable_irq(host->irq);
 		mmc_request_done(mmc, req);
 		return;
 	}
-- 
1.5.6.3

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