| From: Marek Szyprowski <m.szyprowski@samsung.com> |
| Subject: arm: dma-mapping: fix potential endless loop in __dma_page_dev_to_cpu() |
| Date: Wed, 9 Aug 2023 19:27:37 +0200 |
| |
| The D-cache cleaning loop should not call folio_next() beyond the |
| requested region and rely on its parameters. Simply stop looping if left |
| counter reaches zero. |
| |
| This fixes the following endless loop observed by RCU stall on the ARM |
| 32bit Exynos5422-based Odroid-XU3lite board: |
| |
| --->8--- |
| rcu: INFO: rcu_sched self-detected stall on CPU |
| rcu: 0-....: (27320 ticks this GP) idle=e414/1/0x40000002 softirq=36/36 fqs=13044 |
| rcu: (t=27385 jiffies g=-1067 q=34 ncpus=8) |
| CPU: 0 PID: 93 Comm: kworker/0:1H Not tainted 6.5.0-rc5-next-20230807 #6981 |
| Hardware name: Samsung Exynos (Flattened Device Tree) |
| Workqueue: mmc_complete mmc_blk_mq_complete_work |
| PC is at _set_bit+0x28/0x44 |
| LR is at __dma_page_dev_to_cpu+0xdc/0x170 |
| .. |
| _set_bit from __dma_page_dev_to_cpu+0xdc/0x170 |
| __dma_page_dev_to_cpu from dma_direct_unmap_sg+0x100/0x130 |
| dma_direct_unmap_sg from dw_mci_post_req+0x68/0x6c |
| dw_mci_post_req from mmc_blk_mq_post_req+0x34/0x100 |
| mmc_blk_mq_post_req from mmc_blk_mq_complete_work+0x50/0x60 |
| mmc_blk_mq_complete_work from process_one_work+0x20c/0x4d8 |
| process_one_work from worker_thread+0x58/0x54c |
| worker_thread from kthread+0xe0/0xfc |
| kthread from ret_from_fork+0x14/0x2c |
| --->8--- |
| |
| While touching this code, move the set_bit() operation, which deals with |
| atomics, a bit up in the call chain. The new order helps a bit compiler |
| to produce code computing folio_size() only once. |
| |
| Link: https://lkml.kernel.org/r/20230809172737.3574190-1-m.szyprowski@samsung.com |
| Fixes: cc24e9c0895c ("arm: implement the new page table range API") |
| Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> |
| Cc: Matthew Wilcox <willy@infradead.org> |
| Cc: Mike Rapoport (IBM) <rppt@kernel.org> |
| Cc: Russell King <linux@armlinux.org.uk> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| arch/arm/mm/dma-mapping.c | 4 +++- |
| 1 file changed, 3 insertions(+), 1 deletion(-) |
| |
| --- a/arch/arm/mm/dma-mapping.c~arm-implement-the-new-page-table-range-api-fix |
| +++ a/arch/arm/mm/dma-mapping.c |
| @@ -719,8 +719,10 @@ static void __dma_page_dev_to_cpu(struct |
| } |
| |
| while (left >= (ssize_t)folio_size(folio)) { |
| - set_bit(PG_dcache_clean, &folio->flags); |
| left -= folio_size(folio); |
| + set_bit(PG_dcache_clean, &folio->flags); |
| + if (!left) |
| + break; |
| folio = folio_next(folio); |
| } |
| } |
| _ |
