Re: [PATCH] RDMA/core: Prevent soft lockup during large user memory region cleanup

Junxian Huang
2025-11-11T08:19:20Z

On 2025/11/11 15:01, lirongqing wrote:
> From: Li RongQing <lirongqing@baidu.com>
>
> When a process exits with numerous large, pinned memory regions consisting
> of 4KB pages, the cleanup of the memory region through __ib_umem_release()
> may cause soft lockups. This is because unpin_user_page_range_dirty_lock()
> is called in a tight loop for unpin and releasing page without yielding the
> CPU.
>
> Fix the soft lockup by adding cond_resched() calls in __ib_umem_release
>
> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> ---
> drivers/infiniband/core/umem.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
> index c5b6863..70c1520 100644
> --- a/drivers/infiniband/core/umem.c
> +++ b/drivers/infiniband/core/umem.c
> @@ -59,6 +59,7 @@ static void __ib_umem_release(struct ib_device *dev, struct ib_umem *umem, int d
> unpin_user_page_range_dirty_lock(sg_page(sg),
> DIV_ROUND_UP(sg->length, PAGE_SIZE), make_dirty);
>
> + cond_resched();

If the soft lockup is caused by unpin_user_page_range_dirty_lock(),
cond_resched() should probably be inside the for_each_sgtable_sg
loop.

Junxian

> sg_free_append_table(&umem->sgt_append);
> }
>