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| author | Lecopzer Chen <lecopzer.chen@mediatek.com> | 2020-12-14 19:13:23 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-15 12:13:46 -0800 |
| commit | a4efc174b382fcdb62e2d90d39e78a274a975e38 (patch) | |
| tree | 2f5fcc927698c6b47cbac57eaaed34e8dd0907b3 /mm | |
| parent | d85c6db4cc61bd8299f68534bf7ea2f717f49539 (diff) | |
| download | linux-a4efc174b382fcdb62e2d90d39e78a274a975e38.tar.gz linux-a4efc174b382fcdb62e2d90d39e78a274a975e38.tar.bz2 linux-a4efc174b382fcdb62e2d90d39e78a274a975e38.zip | |
mm/cma.c: remove redundant cma_mutex lock
The cma_mutex which protects alloc_contig_range() was first appeared in
commit 7ee793a62fa8c ("cma: Remove potential deadlock situation"), at that
time, there is no guarantee the behavior of concurrency inside
alloc_contig_range().
After commit 2c7452a075d4db2dc ("mm/page_isolation.c: make
start_isolate_page_range() fail if already isolated")
> However, two subsystems (CMA and gigantic
> huge pages for example) could attempt operations on the same range. If
> this happens, one thread may 'undo' the work another thread is doing.
> This can result in pageblocks being incorrectly left marked as
> MIGRATE_ISOLATE and therefore not available for page allocation.
The concurrency inside alloc_contig_range() was clarified.
Now we can find that hugepage and virtio call alloc_contig_range() without
any lock, thus cma_mutex is "redundant" in cma_alloc() now.
Link: https://lkml.kernel.org/r/20201020102241.3729-1-lecopzer.chen@mediatek.com
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: YJ Chiang <yj.chiang@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/cma.c | 4 |
1 files changed, 1 insertions, 3 deletions
@@ -38,7 +38,6 @@ struct cma cma_areas[MAX_CMA_AREAS]; unsigned cma_area_count; -static DEFINE_MUTEX(cma_mutex); phys_addr_t cma_get_base(const struct cma *cma) { @@ -454,10 +453,9 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align, mutex_unlock(&cma->lock); pfn = cma->base_pfn + (bitmap_no << cma->order_per_bit); - mutex_lock(&cma_mutex); ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA, GFP_KERNEL | (no_warn ? __GFP_NOWARN : 0)); - mutex_unlock(&cma_mutex); + if (ret == 0) { page = pfn_to_page(pfn); break; |