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Date: Tue, 12 Oct 2010 16:28:45 +0200
From: Tomas Henzl <thenzl@...hat.com>
To: "Yang, Bo" <Bo.Yang@....com>
CC: James Bottomley <James.Bottomley@...e.de>,
bo yang <boyang1288@...il.com>,
"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
"akpm@...l.org" <akpm@...l.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Daftardar, Jayant" <Jayant.Daftardar@....com>
Subject: Re: PATCH 1/5] scsi: megaraid_sas - Add Online Controller Reset to
MegaRAID SAS drive
On 10/11/2010 05:37 PM, Yang, Bo wrote:
> Tomas,
>
> The reason the driver does flush_scheduled_work() is driver did cancel_delayed_work(). I am not sure driver need to call flush_scheduled_work() if the scheduled work already done, but I will test this changes and submit another patch as soon as it works fine.
>
Driver needs to call flush_scheduled_work() because you are adding in this patch a new workqueue:
INIT_WORK(&instance->work_init, process_fw_state_change_wq); so calling the flush_scheduled_work()
only if a certain condition is met is the problem. If the condition comes true for both workqueues
then it would be fine, but I think that it isn't so.
With this patch we could have a started workqueue (with a long 30 sec sleep) and when the module
is removed then probably a memory corruption etc.
> This change should not be the part of this patch, we would have the new patch submit after the verification.
>
I would prefer to have it in one patch, but if it is for you easier, then do it as you wish.
Tomas
> Regards,
>
> Bo Yang
>
> -----Original Message-----
> From: Tomas Henzl [mailto:thenzl@...hat.com]
> Sent: Monday, October 11, 2010 9:21 AM
> To: Yang, Bo
> Cc: James Bottomley; bo yang; linux-scsi@...r.kernel.org; akpm@...l.org; linux-kernel@...r.kernel.org
> Subject: Re: PATCH 1/5] scsi: megaraid_sas - Add Online Controller Reset to MegaRAID SAS drive
>
> On 10/11/2010 02:55 PM, Yang, Bo wrote:
>
>> Tomas,
>>
>>
>>
>>> Another correction - flush_scheduled_work is already present in megass_detach_one
>>> it only should be moved away from the if statement.
>>>
>>>
>> The flush_scheduled_work is for schedule_delayed_work(). We need to flush it and remove.
>>
>>
> I'm not saying it should be removed, I think a move outside from the 'if' block
> makes it work for ev->hotplug_work and for the newly added instance->work_init
>
>
> diff --git a/drivers/scsi/megaraid/megaraid_sas.c b/drivers/scsi/megaraid/megaraid_sas.c
> index 55951f4..7773707 100644
> --- a/drivers/scsi/megaraid/megaraid_sas.c
> +++ b/drivers/scsi/megaraid/megaraid_sas.c
> @@ -4088,9 +4088,9 @@ static void __devexit megasas_detach_one(struct pci_dev *pdev)
> struct megasas_aen_event *ev = instance->ev;
> cancel_delayed_work(
> (struct delayed_work *)&ev->hotplug_work);
> - flush_scheduled_work();
> - instance->ev = NULL;
> }
> + flush_scheduled_work();
> + instance->ev = NULL;
>
> tasklet_kill(&instance->isr_tasklet);
>
> --
>
>
>> -----Original Message-----
>> From: Tomas Henzl [mailto:thenzl@...hat.com]
>> Sent: Saturday, October 09, 2010 4:38 PM
>> To: James Bottomley
>> Cc: bo yang; linux-scsi@...r.kernel.org; akpm@...l.org; linux-kernel@...r.kernel.org; Yang, Bo
>> 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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