[PATCH V3 25/30] omap_hsmmc: prevent races with irq handler

Adrian Hunter
2009-09-09T11:59:41Z

>From 8dc8e911b67f5c77e95c203908ff2ad7ce728b13 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 adding a spinlock.

Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
---
drivers/mmc/host/omap_hsmmc.c | 25 +++++++++++++++++++++++++
1 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
index 205cc3a..50c7f94 100644
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c
@@ -146,6 +146,8 @@ struct mmc_omap_host {
struct work_struct mmc_carddetect_work;
void __iomem *base;
resource_size_t mapbase;
+ spinlock_t irq_lock; /* Prevent races with irq handler */
+ unsigned long flags;
unsigned int id;
unsigned int dma_len;
unsigned int dma_sg_idx;
@@ -452,6 +454,14 @@ 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 spinlock is unlocked
+ * by the interrupt handler, otherwise (i.e. for a new request) it is
+ * unlocked here.
+ */
+ if (!in_interrupt())
+ spin_unlock_irqrestore(&host->irq_lock, host->flags);
+
OMAP_HSMMC_WRITE(host->base, ARG, cmd->arg);
OMAP_HSMMC_WRITE(host->base, CMD, cmdreg);
}
@@ -614,11 +624,14 @@ static irqreturn_t mmc_omap_irq(int irq, void *dev_id)
struct mmc_data *data;
int end_cmd = 0, end_trans = 0, status;

+ spin_lock(&host->irq_lock);
+
if (host->mrq == NULL) {
OMAP_HSMMC_WRITE(host->base, STAT,
OMAP_HSMMC_READ(host->base, STAT));
/* Flush posted write */
OMAP_HSMMC_READ(host->base, STAT);
+ spin_unlock(&host->irq_lock);
return IRQ_HANDLED;
}

@@ -683,6 +696,8 @@ static irqreturn_t mmc_omap_irq(int irq, void *dev_id)
if ((end_trans || (status & TC)) && host->mrq)
mmc_omap_xfer_done(host, data);

+ spin_unlock(&host->irq_lock);
+
return IRQ_HANDLED;
}

@@ -1011,6 +1026,13 @@ 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())
+ spin_lock_irqsave(&host->irq_lock, host->flags);
WARN_ON(host->mrq != NULL);
host->mrq = req;
err = mmc_omap_prepare_data(host, req);
@@ -1019,6 +1041,8 @@ 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())
+ spin_unlock_irqrestore(&host->irq_lock, host->flags);
mmc_request_done(mmc, req);
return;
}
@@ -1573,6 +1597,7 @@ static int __init omap_mmc_probe(struct platform_device *pdev)
mmc->f_max = 52000000;

sema_init(&host->sem, 1);
+ spin_lock_init(&host->irq_lock);

host->iclk = clk_get(&pdev->dev, "ick");
if (IS_ERR(host->iclk)) {
--
1.5.6.3