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

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Message-ID: <2e7c2be8-dc58-4e18-9297-e8690565583b@acm.org>
Date: Thu, 24 Jul 2025 09:02:54 -0700
From: Bart Van Assche <bvanassche@....org>
To: André Draszik <andre.draszik@...aro.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>
Cc: Peter Griffin <peter.griffin@...aro.org>,
 Tudor Ambarus <tudor.ambarus@...aro.org>,
 Will McVicker <willmcvicker@...gle.com>,
 Manivannan Sadhasivam <mani@...nel.org>, 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 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.

Thanks,

Bart.