Hello Ziyang,
On Sat, May 14, 2022 at 11:57 AM Ziyang Xuan
<[email protected]> wrote:
> t7xx_cldma_clear_rxq() call t7xx_cldma_alloc_and_map_skb() in spin_lock
> context, But __dev_alloc_skb() in t7xx_cldma_alloc_and_map_skb() uses
> GFP_KERNEL, that will introduce scheduling factor in spin_lock context.
>
> Replace GFP_KERNEL with GFP_ATOMIC to fix it.
Would not it will be more reliable to just rework
t7xx_cldma_clear_rxq() to avoid calling t7xx_cldma_alloc_and_map_skb()
under the spin lock instead of doing each allocation with GFP_ATOMIC?
E.g. t7xx_cldma_gpd_rx_from_q() calls t7xx_cldma_alloc_and_map_skb()
avoiding any lock holding.
--
Sergey
On 5/16/2022 1:36 PM, Sergey Ryazanov wrote:
> Hello Ziyang,
>
> On Sat, May 14, 2022 at 11:57 AM Ziyang Xuan
> <[email protected]> wrote:
>> t7xx_cldma_clear_rxq() call t7xx_cldma_alloc_and_map_skb() in spin_lock
>> context, But __dev_alloc_skb() in t7xx_cldma_alloc_and_map_skb() uses
>> GFP_KERNEL, that will introduce scheduling factor in spin_lock context.
>>
>> Replace GFP_KERNEL with GFP_ATOMIC to fix it.
> Would not it will be more reliable to just rework
> t7xx_cldma_clear_rxq() to avoid calling t7xx_cldma_alloc_and_map_skb()
> under the spin lock instead of doing each allocation with GFP_ATOMIC?
> E.g. t7xx_cldma_gpd_rx_from_q() calls t7xx_cldma_alloc_and_map_skb()
> avoiding any lock holding.
t7xx_cldma_clear_rxq() is a helper for t7xx_cldma_clear_all_qs() which
is only called by t7xx_cldma_exception() after stopping CLDMA, so it
should be OK to remove the spin lock from t7xx_cldma_clear_rxq().