linux-kernel - Re: [PATCH v2 1/3] scsi: ufs: core: Remove redundant host

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Message-ID: <8e1ec6a0-38db-414e-90da-4d04ea8d6be2@acm.org>
Date: Tue, 22 Oct 2024 09:51:26 -0700
From: Bart Van Assche <bvanassche@....org>
To: Avri Altman <avri.altman@....com>,
 "Martin K . Petersen" <martin.petersen@...cle.com>
Cc: linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] scsi: ufs: core: Remove redundant host_lock calls
 around UTMRLDBR.

On 10/22/24 12:43 AM, Avri Altman wrote:
> @@ -6877,13 +6874,13 @@ static irqreturn_t ufshcd_check_errors(struct ufs_hba *hba, u32 intr_status)
>    */
>   static irqreturn_t ufshcd_tmc_handler(struct ufs_hba *hba)
>   {
> -	unsigned long flags, pending, issued;
> +	unsigned long flags;
> +	unsigned long pending = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL);
> +	unsigned long issued = hba->outstanding_tasks & ~pending;
>   	irqreturn_t ret = IRQ_NONE;
>   	int tag;
>   
>   	spin_lock_irqsave(hba->host->host_lock, flags);
> -	pending = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL);
> -	issued = hba->outstanding_tasks & ~pending;

Please keep the 'pending' and 'issued' assignments in the function body. 
Initializing variables in the declaration block is fine but adding code 
in the declaration block that has side effects is a bit controversial.

>   	for_each_set_bit(tag, &issued, hba->nutmrs) {
>   		struct request *req = hba->tmf_rqs[tag];
>   		struct completion *c = req->end_io_data;

Would it be sufficient to hold the SCSI host lock around the 
hba->outstanding_tasks read only? I don't think that the
for_each_set_bit() loop needs to be protected with the SCSI host lock.

Otherwise this patch looks good to me.

Thanks,

Bart.