linux-kernel - Re: [PATCH v2 4/6] scsi: pm8001: Use sas_task_find

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Date:   Fri, 30 Sep 2022 12:05:59 +0100
From:   John Garry <john.garry@...wei.com>
To:     Jinpu Wang <jinpu.wang@...os.com>, <damien.lemoal@....com>
CC:     <jejb@...ux.ibm.com>, <martin.petersen@...cle.com>, <hare@...e.de>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>, <ipylypiv@...gle.com>,
        <changyuanl@...gle.com>, <hch@....de>, <yanaijie@...wei.com>
Subject: Re: [PATCH v2 4/6] scsi: pm8001: Use sas_task_find_rq() for tagging

On 30/09/2022 11:20, John Garry wrote:
> BTW, I do notice that we still have this global lock in delivery path 
> which should be removed at some stage:
> > int mvs_queue_command(struct sas_task *task, gfp_t gfp_flags)
> {
>      ...
> 
>      spin_lock_irqsave(&mvi->lock, flags);
>      rc = mvs_task_prep(task, mvi, is_tmf, tmf, &pass);
>      ...
>      spin_unlock_irqrestore(&mvi->lock, flags);
> }
> 

oops... that's mvsas. But pm8001 does still use a big lock (which we 
should get rid off):

int pm8001_queue_command(struct sas_task *task, gfp_t gfp_flags)
{
	...
	pm8001_dbg(pm8001_ha, IO, "pm8001_task_exec device\n");

	spin_lock_irqsave(&pm8001_ha->lock, flags);


Thanks,
John

> That really will affect performance...