SDIO: Fix deadlock when destroying IRQ work queue

This patch fixes a deadlock in sdio_release_irq. If there was work
scheduled that had not yet claimed the mmc host at the point of calling
sdio_release_irq, then it never could claim the host since the caller
of sdio_release_irq already had claimed the host.

Now the host is released to allow the work queue to flush out any
pending work. A check is also added to make sure IRQ:s are not
enabled as a consequence of this cleanup work.

ST-Ericsson Linux next: NA
ST-Ericsson ID: ER339608
ST-Ericsson FOSS-OUT ID: Trivial

Change-Id: I700719e10c779d69561f0cc66b1df5fb41cbd21e
Signed-off-by: Stefan Nilsson XK <stefan.xk.nilsson@stericsson.com>
Reviewed-on: http://gerrit.lud.stericsson.com/gerrit/24675
Reviewed-by: Ulf HANSSON <ulf.hansson@stericsson.com>
Reviewed-by: QATEST

1 files changed, 24 insertions, 2 deletions

diff --git a/drivers/mmc/core/sdio_irq.c b/drivers/mmc/core/sdio_irq.c
index 7502ba3ebda..ff6bdaef680 100644
--- a/drivers/mmc/core/sdio_irq.c
+++ b/drivers/mmc/core/sdio_irq.c
@@ -104,9 +104,13 @@ static void sdio_irq_work_func(struct work_struct *work)
 	 */
 	mmc_claim_host(host);
 
-	ret = process_sdio_pending_irqs(host->card);
+	/* Check if there are any subscribers to IRQ:s */
+	if (!host->sdio_irqs) {
+		mmc_release_host(host);
+		return;
+	}
 
-	mmc_release_host(host);
+	ret = process_sdio_pending_irqs(host->card);
 
 	if (host->caps & MMC_CAP_SDIO_IRQ)
 		host->ops->enable_sdio_irq(host, true);
@@ -127,6 +131,8 @@ static void sdio_irq_work_func(struct work_struct *work)
 				   &host->sdio_irq_work,
 				   msecs_to_jiffies(host->sdio_poll_period));
 	}
+
+	mmc_release_host(host);
 }
 
 static int sdio_card_irq_get(struct mmc_card *card)
@@ -173,9 +179,25 @@ static int sdio_card_irq_put(struct mmc_card *card)
 
 	if (!--host->sdio_irqs) {
 		host->ops->enable_sdio_irq(host, false);
+
+		/*
+		 * Temporarily release the host in order to complete
+		 * any pending work before destroying the work queue.
+		 *
+		 * There is a theroetical chance of messing up here,
+		 * if a calling driver is waiting to claim the host
+		 * in order to claim an SDIO IRQ, and that call falls through
+		 * while releasing the IRQ:s here, there is no guarantee
+		 * that that IRQ:s will be reliably turned on or off.
+		 * This will be fixed in a coming patch, but this solution
+		 * is deemed good enough for now since it fixes an obvious
+		 * error and the failing case deemed not likely to happen.
+		 */
+		mmc_release_host(card->host);
 		cancel_delayed_work_sync(&host->sdio_irq_work);
 		destroy_workqueue(host->sdio_irq_workqueue);
 		host->sdio_irq_workqueue = NULL;
+		mmc_claim_host(card->host);
 	}
 
 	return 0;