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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@nokia.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@nokia.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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