Commit e5887103 authored by Alexander Kochetkov's avatar Alexander Kochetkov Committed by Vinod Koul
Browse files

dmaengine: pl330: fix descriptor allocation fail 



If two concurrent threads call pl330_get_desc() when DMAC descriptor
pool is empty it is possible that allocation for one of threads will fail
with message:

kernel: dma-pl330 20078000.dma-controller: pl330_get_desc:2469 ALERT!

Here how that can happen. Thread A calls pl330_get_desc() to get
descriptor. If DMAC descriptor pool is empty pl330_get_desc() allocates
new descriptor on shared pool using add_desc() and then get newly
allocated descriptor using pluck_desc(). At the same time thread B calls
pluck_desc() and take newly allocated descriptor. In that case descriptor
allocation for thread A will fail.

Using on-stack pool for new descriptor allow avoid the issue described.
The patch modify pl330_get_desc() to use on-stack pool for allocation
new descriptors.

Signed-off-by: default avatarAlexander Kochetkov <al.kochet@gmail.com>
Tested-by: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: default avatarVinod Koul <vinod.koul@intel.com>
parent 2bd6bf03

drivers/dma/pl330.c

+20 −19
Original line number Diff line number Diff line
@@ -2390,7 +2390,8 @@ static inline void _init_desc(struct dma_pl330_desc *desc) 
}



/* Returns the number of descriptors added to the DMAC pool */

static int add_desc(struct pl330_dmac *pl330, gfp_t flg, int count)

static int add_desc(struct list_head *pool, spinlock_t *lock,

		    gfp_t flg, int count)

{

	struct dma_pl330_desc *desc;

	unsigned long flags;
@@ -2400,27 +2401,28 @@ static int add_desc(struct pl330_dmac *pl330, gfp_t flg, int count) 
	if (!desc)

		return 0;



	spin_lock_irqsave(&pl330->pool_lock, flags);

	spin_lock_irqsave(lock, flags);



	for (i = 0; i < count; i++) {

		_init_desc(&desc[i]);

		list_add_tail(&desc[i].node, &pl330->desc_pool);

		list_add_tail(&desc[i].node, pool);

	}



	spin_unlock_irqrestore(&pl330->pool_lock, flags);

	spin_unlock_irqrestore(lock, flags);



	return count;

}



static struct dma_pl330_desc *pluck_desc(struct pl330_dmac *pl330)

static struct dma_pl330_desc *pluck_desc(struct list_head *pool,

					 spinlock_t *lock)

{

	struct dma_pl330_desc *desc = NULL;

	unsigned long flags;



	spin_lock_irqsave(&pl330->pool_lock, flags);

	spin_lock_irqsave(lock, flags);



	if (!list_empty(&pl330->desc_pool)) {

		desc = list_entry(pl330->desc_pool.next,

	if (!list_empty(pool)) {

		desc = list_entry(pool->next,

				struct dma_pl330_desc, node);



		list_del_init(&desc->node);
@@ -2429,7 +2431,7 @@ static struct dma_pl330_desc *pluck_desc(struct pl330_dmac *pl330) 
		desc->txd.callback = NULL;

	}



	spin_unlock_irqrestore(&pl330->pool_lock, flags);

	spin_unlock_irqrestore(lock, flags);



	return desc;

}
@@ -2441,20 +2443,18 @@ static struct dma_pl330_desc *pl330_get_desc(struct dma_pl330_chan *pch) 
	struct dma_pl330_desc *desc;



	/* Pluck one desc from the pool of DMAC */

	desc = pluck_desc(pl330);

	desc = pluck_desc(&pl330->desc_pool, &pl330->pool_lock);



	/* If the DMAC pool is empty, alloc new */

	if (!desc) {

		if (!add_desc(pl330, GFP_ATOMIC, 1))

			return NULL;

		DEFINE_SPINLOCK(lock);

		LIST_HEAD(pool);



		/* Try again */

		desc = pluck_desc(pl330);

		if (!desc) {

			dev_err(pch->dmac->ddma.dev,

				"%s:%d ALERT!\n", __func__, __LINE__);

		if (!add_desc(&pool, &lock, GFP_ATOMIC, 1))

			return NULL;

		}



		desc = pluck_desc(&pool, &lock);

		WARN_ON(!desc || !list_empty(&pool));

	}



	/* Initialize the descriptor */
@@ -2868,7 +2868,8 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id) 
	spin_lock_init(&pl330->pool_lock);



	/* Create a descriptor pool of default size */

	if (!add_desc(pl330, GFP_KERNEL, NR_DEFAULT_DESC))

	if (!add_desc(&pl330->desc_pool, &pl330->pool_lock,

		      GFP_KERNEL, NR_DEFAULT_DESC))

		dev_warn(&adev->dev, "unable to allocate desc\n");



	INIT_LIST_HEAD(&pd->channels);

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