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author | Laura Abbott <lauraa@codeaurora.org> | 2014-02-25 11:01:19 -0800 |
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committer | Marek Szyprowski <m.szyprowski@samsung.com> | 2014-05-15 12:14:21 +0200 |
commit | 7ee793a62fa8c544f8b844e6e87b2d8e8836b219 (patch) | |
tree | 5885be219592f9cf5a1cb2f81efda7148ad3019a /drivers/base | |
parent | d6d211db37e75de2ddc3a4f979038c40df7cc79c (diff) | |
download | linux-7ee793a62fa8c544f8b844e6e87b2d8e8836b219.tar.gz linux-7ee793a62fa8c544f8b844e6e87b2d8e8836b219.tar.bz2 linux-7ee793a62fa8c544f8b844e6e87b2d8e8836b219.zip |
cma: Remove potential deadlock situation
CMA locking is currently very coarse. The cma_mutex protects both
the bitmap and avoids concurrency with alloc_contig_range. There
are several situations which may result in a deadlock on the CMA
mutex currently, mostly involving AB/BA situations with alloc and
free. Fix this issue by protecting the bitmap with a mutex per CMA
region and use the existing mutex for protecting against concurrency
with alloc_contig_range.
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Diffstat (limited to 'drivers/base')
-rw-r--r-- | drivers/base/dma-contiguous.c | 32 |
1 files changed, 25 insertions, 7 deletions
diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c index 165c2c299e57..fe72bac96275 100644 --- a/drivers/base/dma-contiguous.c +++ b/drivers/base/dma-contiguous.c @@ -37,6 +37,7 @@ struct cma { unsigned long base_pfn; unsigned long count; unsigned long *bitmap; + struct mutex lock; }; struct cma *dma_contiguous_default_area; @@ -161,6 +162,7 @@ static int __init cma_activate_area(struct cma *cma) init_cma_reserved_pageblock(pfn_to_page(base_pfn)); } while (--i); + mutex_init(&cma->lock); return 0; } @@ -261,6 +263,13 @@ err: return ret; } +static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count) +{ + mutex_lock(&cma->lock); + bitmap_clear(cma->bitmap, pfn - cma->base_pfn, count); + mutex_unlock(&cma->lock); +} + /** * dma_alloc_from_contiguous() - allocate pages from contiguous area * @dev: Pointer to device for which the allocation is performed. @@ -294,30 +303,41 @@ struct page *dma_alloc_from_contiguous(struct device *dev, int count, mask = (1 << align) - 1; - mutex_lock(&cma_mutex); for (;;) { + mutex_lock(&cma->lock); pageno = bitmap_find_next_zero_area(cma->bitmap, cma->count, start, count, mask); - if (pageno >= cma->count) + if (pageno >= cma->count) { + mutex_unlock(&cma_mutex); break; + } + bitmap_set(cma->bitmap, pageno, count); + /* + * It's safe to drop the lock here. We've marked this region for + * our exclusive use. If the migration fails we will take the + * lock again and unmark it. + */ + mutex_unlock(&cma->lock); pfn = cma->base_pfn + pageno; + mutex_lock(&cma_mutex); ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA); + mutex_unlock(&cma_mutex); if (ret == 0) { - bitmap_set(cma->bitmap, pageno, count); page = pfn_to_page(pfn); break; } else if (ret != -EBUSY) { + clear_cma_bitmap(cma, pfn, count); break; } + clear_cma_bitmap(cma, pfn, count); pr_debug("%s(): memory range at %p is busy, retrying\n", __func__, pfn_to_page(pfn)); /* try again with a bit different memory target */ start = pageno + mask + 1; } - mutex_unlock(&cma_mutex); pr_debug("%s(): returned %p\n", __func__, page); return page; } @@ -350,10 +370,8 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages, VM_BUG_ON(pfn + count > cma->base_pfn + cma->count); - mutex_lock(&cma_mutex); - bitmap_clear(cma->bitmap, pfn - cma->base_pfn, count); free_contig_range(pfn, count); - mutex_unlock(&cma_mutex); + clear_cma_bitmap(cma, pfn, count); return true; } |