Re: [PATCH v1] ufs: core: decouple CQE processing from spinlock critical section

["Peter Wang (王信友)" <peter.wang@mediatek.com>]

On Thu, 2026-05-14 at 09:22 -0700, Bart Van Assche wrote:
> On 5/14/26 1:26 AM, peter.wang@mediatek.com wrote:
> > 4. In both ufshcd_mcq_compl_all_cqes_lock() and
> >     ufshcd_mcq_poll_cqe_lock(), snapshot the starting CQE pointer
> > before
> >     advancing the head slot under the spinlock, then process the
> > collected
> >     CQEs after releasing the lock using the new helper.
> 
> This can't work reliably. ufshcd_mcq_poll_cqe_lock() may be called
> concurrently from different CPU cores, e.g. from a UFS completion
> interrupt and from ufshcd_poll(). Processing CQEs without holding
> hwq->cq_lock may lead to overwriting of CQEs before these have been
> processed.
> 
> Thanks,
> 
> Bart.

Hi Bart,

This is not an issue because the CQ head is protected by cq_lock.
Only the CQEs from head to tail will be processed by ufshcd_poll
or the ISR. The main difference is that these CQEs will be 
processed later, without holding the cq_lock.

Thanks
Peter