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

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Date:   Sun, 15 Dec 2019 06:24:43 +0800
From:   cang@...eaurora.org
To:     Bart Van Assche <bvanassche@....org>
Cc:     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 2019-12-15 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,

Thanks for pointing it out. I noticed that you are changing this
path too in below 2 changes.
https://marc.info/?l=linux-scsi&m=157591520015924&w=2
https://marc.info/?l=linux-scsi&m=157591519915923&w=2

Actually the async works you pointed may also affect your change,
because you may tear down the hba->cmd_queue too early, as there can be
devm commands sent by clock gating, eeh_work and eh_work after that 
point,
meaning when blk_get_request is called in exec_dev_cmd(), hba->cmd_queue
may have been released already.

@@ -8263,6 +8232,7 @@ void ufshcd_remove(struct ufs_hba *hba)
  {
      ufs_bsg_remove(hba);
      ufs_sysfs_remove_nodes(hba->dev);
+    blk_cleanup_queue(hba->cmd_queue);
      scsi_remove_host(hba->host);
      /* disable interrupts */
      ufshcd_disable_intr(hba, hba->intr_mask);

How do you think if I replace my patch with below one?
In this way, you can also move blk_cleanup_queue() behind
cancel_work_sync(eh_work).

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index b5966fa..bd4ae75 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -8251,15 +8251,17 @@ void ufshcd_remove(struct ufs_hba *hba)
         ufs_bsg_remove(hba);
         ufs_sysfs_remove_nodes(hba->dev);
         scsi_remove_host(hba->host);
-       /* disable interrupts */
-       ufshcd_disable_intr(hba, hba->intr_mask);
-       ufshcd_hba_stop(hba, true);
-
         ufshcd_exit_clk_scaling(hba);
         ufshcd_exit_clk_gating(hba);
         if (ufshcd_is_clkscaling_supported(hba))
                 device_remove_file(hba->dev, 
&hba->clk_scaling.enable_attr);
+       cancel_work_sync(&hba->eeh_work);
+       cancel_work_sync(&hba->eh_work);
+       /* disable interrupts */
+       ufshcd_disable_intr(hba, hba->intr_mask);
+       ufshcd_hba_stop(hba, true);
         ufshcd_hba_exit(hba);
+       ufshcd_dealloc_host(hba);
  }
  EXPORT_SYMBOL_GPL(ufshcd_remove);

-- 

Thanks,

Can Guo.