Re: [PATCH net-next] net: wwan: t7xx: fix GFP_KERNEL usage in spin_lock context

[Martinez, Ricardo]

On 5/16/2022 1:36 PM, Sergey Ryazanov wrote:
> Hello Ziyang,
>
> On Sat, May 14, 2022 at 11:57 AM Ziyang Xuan
> <william.xuanziyang@xxxxxxxxxx> 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().