linux-kernel - Re: [PATCH 1/2] scsi: ufs: Put SCSI host after remove it

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Date:   Tue, 17 Dec 2019 08:50:08 +0800
From:   cang@...eaurora.org
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Bart Van Assche <bvanassche@....org>, asutoshd@...eaurora.org,
        nguyenb@...eaurora.org, rnayak@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        saravanak@...gle.com, salyzyn@...gle.com,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        Tomas Winkler <tomas.winkler@...el.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] scsi: ufs: Put SCSI host after remove it

On 2019-12-17 02:05, Greg KH wrote:
> On Mon, Dec 16, 2019 at 10:31:29PM +0800, cang@...eaurora.org wrote:
>> On 2019-12-15 02:32, Bart Van Assche wrote:
>> > On 12/14/19 8:03 AM, Can Guo wrote:
>> > > In ufshcd_remove(), after SCSI host is removed, put it once so that
>> > > its
>> > > resources can be released.
>> > >
>> > > Signed-off-by: Can Guo <cang@...eaurora.org>
>> > >
>> > > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> > > index b5966fa..a86b0fd 100644
>> > > --- a/drivers/scsi/ufs/ufshcd.c
>> > > +++ b/drivers/scsi/ufs/ufshcd.c
>> > > @@ -8251,6 +8251,7 @@ void ufshcd_remove(struct ufs_hba *hba)
>> > >   	ufs_bsg_remove(hba);
>> > >   	ufs_sysfs_remove_nodes(hba->dev);
>> > >   	scsi_remove_host(hba->host);
>> > > +	scsi_host_put(hba->host);
>> > >   	/* disable interrupts */
>> > >   	ufshcd_disable_intr(hba, hba->intr_mask);
>> > >   	ufshcd_hba_stop(hba, true);
>> >
>> > Hi Can,
>> >
>> > The UFS driver may queue work asynchronously and that asynchronous
>> > work may refer to the SCSI host, e.g. ufshcd_err_handler(). Is it
>> > guaranteed that all that asynchronous work has finished before
>> > scsi_host_put() is called?
>> >
>> > Thanks,
>> >
>> > Bart.
>> 
>> Hi Bart,
>> 
>> As SCSI host is allocated in ufshcd_platform_init() during platform
>> drive probe, it is much more appropriate if platform driver calls
>> ufshcd_dealloc_host() in their own drv->remove() path. How do you
>> think if I change it as below? If it is OK to you, please ignore my
>> previous mails.
>> 
>> diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
>> index 3d4582e..ea45756 100644
>> --- a/drivers/scsi/ufs/ufs-qcom.c
>> +++ b/drivers/scsi/ufs/ufs-qcom.c
>> @@ -3239,6 +3239,7 @@ static int ufs_qcom_remove(struct 
>> platform_device
>> *pdev)
>> 
>>         pm_runtime_get_sync(&(pdev)->dev);
>>         ufshcd_remove(hba);
>> +       ufshcd_dealloc_host(hba);
>>         return 0;
>>  }
> 
> Wait, why is this a platform device?  Don't you hang off of a pci
> device?  Or am I missing something earlier in this patchset?
> 
> thanks,
> 
> greg k-h

Hi Greg,

I am not saying someone is a platform device here. My point is
whoever allocates the SCSI host in its drv->probe(), should
de-allocate it in its own drv->remove(), just like what ufshcd-pci.c
does.

Thanks,

Can Guo.