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

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Message-ID: <4CAF70CD.6020307@redhat.com>
Date:	Fri, 08 Oct 2010 21:28:13 +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 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.
>   
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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