linux-kernel - Re: [PATCH] scsi: libsas: Grab the host lock in sas_ata_device_link

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Message-ID: <755d7a9c-427e-024a-8509-449ebc5a00e6@huawei.com>
Date:   Wed, 21 Dec 2022 14:35:08 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        John Garry <john.g.garry@...cle.com>,
        Xingui Yang <yangxingui@...wei.com>, <jejb@...ux.ibm.com>,
        <martin.petersen@...cle.com>, <niklas.cassel@....com>
CC:     <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>, <prime.zeng@...ilicon.com>,
        <kangfenglong@...wei.com>
Subject: Re: [PATCH] scsi: libsas: Grab the host lock in
 sas_ata_device_link_abort()

On 2022/12/21 11:59, Damien Le Moal wrote:
> On 2022/12/21 11:42, Jason Yan wrote:
>> On 2022/12/21 8:36, Damien Le Moal wrote:
>>> On 2022/12/20 23:59, John Garry wrote:
>>>> On 20/12/2022 12:53, Xingui Yang wrote:
>>>>> Grab the host lock in sas_ata_device_link_abort() before calling
>>>>
>>>> This is should be the ata port lock, right? I know that the ata comments
>>>> say differently.
>>>>
>>>>> ata_link_abort(), as the comment in ata_link_abort() mentions.
>>>>>
>>>>
>>>> Can you please add a fixes tag?
>>>>
>>>>> Signed-off-by: Xingui Yang <yangxingui@...wei.com>
>>>>
>>>> Reviewed-by: John Garry <john.g.garry@...cle.com>
>>>>
>>>>> ---
>>>>>     drivers/scsi/libsas/sas_ata.c | 3 +++
>>>>>     1 file changed, 3 insertions(+)
>>>>>
>>>>> diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
>>>>> index f7439bf9cdc6..4f2017b21e6d 100644
>>>>> --- a/drivers/scsi/libsas/sas_ata.c
>>>>> +++ b/drivers/scsi/libsas/sas_ata.c
>>>>> @@ -889,7 +889,9 @@ void sas_ata_device_link_abort(struct domain_device *device, bool force_reset)
>>>>>     {
>>>>>     	struct ata_port *ap = device->sata_dev.ap;
>>>>>     	struct ata_link *link = &ap->link;
>>>>> +	unsigned long flags;
>>>>>     
>>>>> +	spin_lock_irqsave(ap->lock, flags);
>>>>>     	device->sata_dev.fis[2] = ATA_ERR | ATA_DRDY; /* tf status */
>>>>>     	device->sata_dev.fis[3] = ATA_ABORTED; /* tf error */
>>>>>     
>>>>> @@ -897,6 +899,7 @@ void sas_ata_device_link_abort(struct domain_device *device, bool force_reset)
>>>>>     	if (force_reset)
>>>>>     		link->eh_info.action |= ATA_EH_RESET;
>>>>>     	ata_link_abort(link);
>>>
>>> Really need to add lockdep annotations in libata to avoid/catch such bugs...
>>> Will work on that.
>>
>> Actually in libata there are many places calling ata_link_abort() not
>> holding port lock. And some places are holding the real host
>> lock(ata_host->lock) while calling ata_link_abort(). So if you add the
>> lockdep annotations, there may be too many warnings. If these are real
>> issues, we should fix them first.
> 
> libata-EH does most of its work without the port lock held because by the time
> we get EH started, we are guaranteed to be idle with no commands in flight. That
> is why the calls you mention look like "bugs" but are not.

What about the interrupt handler such as ahci_error_intr()? I didn't see 
the callers hold the port lock too. Do they need the port lock?