From: Johannes Thoma <[email protected]> When the size of the requested block is close to the total size of the contigous memory, cma_alloc fails early when no more free memory blocks are found by bitmap_find_next_zero_area_off and the memory areas tested are temporarily busy.
This patch introduces a little extra loop that causes cma_alloc to rescan from the beginning when all checked memory areas are busy. We ran into this problem when a GPU driver tried to allocate cma memory on a busy system, but failed because the memory area was busy. Signed-off-by: Johannes Thoma <[email protected]> --- mm/cma.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/mm/cma.c b/mm/cma.c index c960459..35d68c8 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -368,6 +368,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align) unsigned long pfn = -1; unsigned long start = 0; unsigned long bitmap_maxno, bitmap_no, bitmap_count; + int retries = 10; struct page *page = NULL; int ret; @@ -390,10 +391,21 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align) for (;;) { mutex_lock(&cma->lock); +scan_again: bitmap_no = bitmap_find_next_zero_area_off(cma->bitmap, bitmap_maxno, start, bitmap_count, mask, offset); if (bitmap_no >= bitmap_maxno) { + /* + * Restart from the beginning if all areas were busy. + * This handles false failures when count is close + * to overall CMA size and the checked areas were + * busy temporarily. + */ + if (start != 0 && retries--) { + start = 0; + goto scan_again; + } mutex_unlock(&cma->lock); break; } -- 2.8.0-rc4 _______________________________________________ Kernelnewbies mailing list [email protected] https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
