linux-kernel - Re: [PATCH] scsi: ufs: core: move some irq handling back to hardirq (with time limit)

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Message-ID: <cdpppjy6hljvr3duzc2y2dov27geclujdrvcxpllhazrbyhf7c@z4y7gt6siryy>
Date: Mon, 28 Jul 2025 20:12:30 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: André Draszik <andre.draszik@...aro.org>
Cc: Bart Van Assche <bvanassche@....org>, 
	Alim Akhtar <alim.akhtar@...sung.com>, Avri Altman <avri.altman@....com>, 
	"James E.J. Bottomley" <James.Bottomley@...senpartnership.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Peter Griffin <peter.griffin@...aro.org>, 
	Tudor Ambarus <tudor.ambarus@...aro.org>, Will McVicker <willmcvicker@...gle.com>, kernel-team@...roid.com, 
	linux-arm-msm@...r.kernel.org, linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org
Subject: Re: [PATCH] scsi: ufs: core: move some irq handling back to hardirq
 (with time limit)

On Fri, Jul 25, 2025 at 04:00:42PM GMT, André Draszik wrote:
> On Thu, 2025-07-24 at 09:02 -0700, Bart Van Assche wrote:
> > On 7/24/25 2:54 AM, André Draszik wrote:
> > > @@ -5656,19 +5689,39 @@ static int ufshcd_poll(struct Scsi_Host *shost, unsigned int queue_num)
> > >   	WARN_ONCE(completed_reqs & ~hba->outstanding_reqs,
> > >   		  "completed: %#lx; outstanding: %#lx\n", completed_reqs,
> > >   		  hba->outstanding_reqs);
> > > -	if (queue_num == UFSHCD_POLL_FROM_INTERRUPT_CONTEXT) {
> > > -		/* Do not complete polled requests from interrupt context. */
> > > +	if (time_limit) {
> > > +		/* Do not complete polled requests from hardirq context. */
> > >   		ufshcd_clear_polled(hba, &completed_reqs);
> > >   	}
> > 
> > This if-statement and the code inside the if-statement probably can be
> > left out. This if-statement was introduced at a time when the block
> > layer did not support completing polled requests from interrupt context.
> > I think that commit b99182c501c3 ("bio: add pcpu caching for non-polling
> > bio_put") enabled support for completing polled requests from interrupt
> > context. Since this patch touches that if-statement, how about removing
> > it with a separate patch that comes before this patch? Polling can be
> > enabled by adding --hipri=1 to the fio command line and by using an I/O
> > engine that supports polling, e.g. pvsync2 or io_uring.
> 
> Bart, thank you for taking the time to explain and the background info on
> this, very helpful!
> 

Yeah, I realized it after hitting 'y' in mutt. Added now.

- Mani

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