linux-kernel - Re: PATCH 1/5] scsi: megaraid_sas - Add Online Controller Reset to MegaRAID SAS drive

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Message-ID: <4CB0D2AF.7080609@redhat.com>
Date:	Sat, 09 Oct 2010 22:38:07 +0200
From:	Tomas Henzl <thenzl@...hat.com>
To:	James Bottomley <James.Bottomley@...e.de>
CC:	bo yang <boyang1288@...il.com>, linux-scsi@...r.kernel.org,
	akpm@...l.org, linux-kernel@...r.kernel.org, bo.yang@....com
Subject: Re: PATCH 1/5] scsi: megaraid_sas - Add Online Controller Reset to
 MegaRAID SAS drive

On 10/08/2010 09:28 PM, Tomas Henzl wrote:
> On 10/08/2010 06:39 PM, James Bottomley wrote:
>   
>> On Fri, 2010-10-08 at 17:51 +0200, Tomas Henzl wrote:
>>   
>>     
>>> On 09/23/2010 04:36 AM, bo yang wrote:
>>>     
>>>       
>>>> This patch is too big.  I am using attachment to submit.  Please
>>>> use attached file to apply.  Also let me know if it can't be accepted.
>>>>
>>>> To add the Online controller reset support, driver need to do:
>>>> a). reset the controller chips -- Xscale and Gen2 which will change
>>>> the function calls and add the reset function related to this two
>>>> chips.
>>>> b). during the reset, driver will store the pending cmds which not
>>>> returned by FW to driver's pending queue.  Driver will re-issue those
>>>> pending cmds again to FW after the OCR finished.
>>>> c). In driver's timeout routine, driver will report to OS as reset.
>>>> Also driver's queue routine will block the cmds until the OCR
>>>> finished.
>>>> d). in Driver's ISR routine, if driver get the FW state as state
>>>> change, FW in Failure status and FW support online controller
>>>> reset (OCR), driver will start to do the controller reset.
>>>> e). In driver's IOCTL routine, the application cmds will wait for the
>>>> OCR to finish, then issue the cmds to FW.
>>>>
>>>> Signed-off-by Bo Yang<bo.yang@....com>
>>>>
>>>> ---
>>>>  drivers/scsi/megaraid/megaraid_sas.c |  756 ++++++++++++++++++++++++++++++++---
>>>>  drivers/scsi/megaraid/megaraid_sas.h |   88 +++-
>>>>  2 files changed, 787 insertions(+), 57 deletions(-)
>>>>       
>>>>         
>>> Hi Bo,
>>> in the workqueue function you sleep for 30s,
>>> it's scheduled here - schedule_work(&instance->work_init);
>>>
>>> +process_fw_state_change_wq(struct work_struct *work)
>>> +{
>>> ...
>>> +		/*waitting for about 20 second before start the second init*/
>>> +		for (wait = 0; wait < 30; wait++) {
>>> +			msleep(1000);
>>> +		}
>>>     
>>>       
>> this lot should be ssleep(20) if you want a 20 sec sleep.
>>   
>>     
> please do that on every place where you use the 
> "for (wait = 0; wait < n; wait++) msleep(1000);" construction
>
>   
>>> - this is not a good practice to sleep for a so long time I think
>>>     
>>>       
> this long sleep might might be ok, if the workqueue is used only rarely
> is it so?
>
>   
>>> - you should use in your exit function some synchronization 
>>>   for example 'cancel_work_sync', without that if someone rmmods your 
>>>   module, it could then lead to a memory corruption
>>>     
>>>       
>> Actually flush_scheduled_work() should be fine ... it will force the
>> module removal to wait for completion ... cancellation can be error
>> prone, so just forcing the wait sounds easier.
>>   
>>     
Another correction - flush_scheduled_work is already present in megass_detach_one
it only should be moved away from the if statement.


> someone told that cancel_work_sync is safer then flush_scheduled_work
> but I'm not an expert, so ok 
>
> Tomas
>
>   
>> James
>>
>>
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>>   
>>     
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