linux-kernel - Re: [PATCH] scsi: pm8001: Fix data race in sysfs SAS address read

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Message-ID: <2c210e30-e7bd-4b70-ad4e-cc7a1bbb5309@acm.org>
Date: Thu, 15 Jan 2026 09:24:34 -0800
From: Bart Van Assche <bvanassche@....org>
To: Chengfeng Ye <dg573847474@...il.com>,
 "James E . J . Bottomley" <James.Bottomley@...senPartnership.com>,
 "Martin K . Petersen" <martin.petersen@...cle.com>
Cc: Jack Wang <jinpu.wang@...ud.ionos.com>, linux-scsi@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: pm8001: Fix data race in sysfs SAS address read

On 1/15/26 9:11 AM, Chengfeng Ye wrote:
> diff --git a/drivers/scsi/pm8001/pm8001_ctl.c b/drivers/scsi/pm8001/pm8001_ctl.c
> index cbfda8c04e95..e49f11969b3b 100644
> --- a/drivers/scsi/pm8001/pm8001_ctl.c
> +++ b/drivers/scsi/pm8001/pm8001_ctl.c
> @@ -311,8 +311,15 @@ static ssize_t pm8001_ctl_host_sas_address_show(struct device *cdev,
>   	struct Scsi_Host *shost = class_to_shost(cdev);
>   	struct sas_ha_struct *sha = SHOST_TO_SAS_HA(shost);
>   	struct pm8001_hba_info *pm8001_ha = sha->lldd_ha;
> -	return sysfs_emit(buf, "0x%016llx\n",
> -			be64_to_cpu(*(__be64 *)pm8001_ha->sas_addr));
> +	unsigned long flags;
> +	ssize_t ret;
> +
> +	spin_lock_irqsave(&pm8001_ha->lock, flags);
> +	ret = sysfs_emit(buf, "0x%016llx\n",
> +			 be64_to_cpu(*(__be64 *)pm8001_ha->sas_addr));
> +	spin_unlock_irqrestore(&pm8001_ha->lock, flags);
> +
> +	return ret;
>   }
>   static DEVICE_ATTR(host_sas_address, S_IRUGO,
>   		   pm8001_ctl_host_sas_address_show, NULL);

Why isn't READ_ONCE() sufficient? And why explicit spin_lock_irqsave() 
and spin_unlock_irqrestore() calls instead of using scoped_guard()?

Bart.