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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: Alexander Kochetkov <al.kochet@gmail.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
This commit is contained in:
Alexander Kochetkov 2017-10-04 14:37:23 +03:00 committed by Vinod Koul
parent 2bd6bf03f4
commit e588710311
1 changed files with 20 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
drivers/dma/pl330.c
View File

@ -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))
DEFINE_SPINLOCK(lock);
LIST_HEAD(pool);
if (!add_desc(&pool, &lock, GFP_ATOMIC, 1))
return NULL;
/* Try again */
desc = pluck_desc(pl330);
if (!desc) {
dev_err(pch->dmac->ddma.dev,
"%s:%d ALERT!\n", __func__, __LINE__);
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);