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SubjectRe: [PATCH 1/2] [SCSI] pm8001: Fix bogus interrupt state flag issue.
From
Hi Mark,

Thanks for your review.

Few queries:

1. Similar changes have been made in mpi_sata_completion() surrounding
spin_*lock_irq*(&t->task->state_lock)
Should those changes also need to revert back ?

>
> The change you did was not inert, and result in the IRQ being disabled upon exit should a
> SAS_TASK_STATE_ABORTED task state condition occur then following block will enable IRQ.

2. I could not get this point.
If "SAS_TASK_STATE_ABORTED" task state condition occurs then following
block will enable IRQ.

if (unlikely((t->task_state_flags & SAS_TASK_STATE_ABORTED))) {
spin_unlock_irq(&t->task_state_lock);
// HERE IRQ will be enabled.
.......
pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
}
3. How bad will be "spin_lock_irq / spin_unlock_irq" in this case compared to
"spin_lock_irqsave / spin_unlock_irqrestore "



Regards
Santosh

>
> I propose (annotated below) you leave the flags automatic variable, but uninitialized. The changes surrounding spin_*lock_irq*(&pm8001_ha->lock, flags) are OK, but revert back the changes surrounding the spin_*lock_irq*(&t->task->state_lock,flags) so that lock would be properly nested.
>
> To be pedantic, and to be more correct, this code should have spawned a work queue task to perform the t->task_done(t) operation in a separate thread rather than inline and precariously unlocked; but that would be beyond the scope of these changes and should be left for future work to decide if it is even necessary. Not sure how such a change would affect performance (using the work queue) ... so I am 'afraid' of pushing such a change in any case given the relatively reliable operation of this driver (and the dynamic nature of the changes Dan is making to the SATA side of things for instance ;-} ).
>
> I am sorry for taking so long to get to the task of reviewing this (and the previous) code. I look forward to your comments.
>
> Sincerely -- Mark Salyzyn
>
> On Feb 26, 2012, at 8:33 AM, santosh nayak wrote:
>
>> @@ -2207,7 +2206,6 @@ mpi_sata_completion(struct pm8001_hba_info *pm8001_ha, void *piomb)
>> static void mpi_sata_event(struct pm8001_hba_info *pm8001_ha , void *piomb)
>> {
>>       struct sas_task *t;
>> -     unsigned long flags = 0;
> MGS>    unsigned long flags;
>>       struct task_status_struct *ts;
>>       struct pm8001_ccb_info *ccb;
>>       struct pm8001_device *pm8001_dev;
>> @@ -2287,9 +2285,9 @@ static void mpi_sata_event(struct pm8001_hba_info *pm8001_ha , void *piomb)
>>                       ts->stat = SAS_QUEUE_FULL;
>>                       pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
>>                       mb();/*ditto*/
>> -                     spin_unlock_irqrestore(&pm8001_ha->lock, flags);
>> +                     spin_unlock_irq(&pm8001_ha->lock);
>>                       t->task_done(t);
>> -                     spin_lock_irqsave(&pm8001_ha->lock, flags);
>> +                     spin_lock_irq(&pm8001_ha->lock);
>>                       return;
>>               }
>>               break;
>> @@ -2387,31 +2385,31 @@ static void mpi_sata_event(struct pm8001_hba_info *pm8001_ha , void *piomb)
>>               ts->stat = SAS_OPEN_TO;
>>               break;
>>       }
>> -     spin_lock_irqsave(&t->task_state_lock, flags);
>> +     spin_lock_irq(&t->task_state_lock);
> MGS>    spin_lock_irqsave(&t->task_state_lock, flags);
>>       t->task_state_flags &= ~SAS_TASK_STATE_PENDING;
>>       t->task_state_flags &= ~SAS_TASK_AT_INITIATOR;
>>       t->task_state_flags |= SAS_TASK_STATE_DONE;
>>       if (unlikely((t->task_state_flags & SAS_TASK_STATE_ABORTED))) {
>> -             spin_unlock_irqrestore(&t->task_state_lock, flags);
>> +             spin_unlock_irq(&t->task_state_lock);
> MGS>            spin_unlock_irqrestore(&t->task_state_lock, flags);
>>               PM8001_FAIL_DBG(pm8001_ha,
>>                       pm8001_printk("task 0x%p done with io_status 0x%x"
>>                       " resp 0x%x stat 0x%x but aborted by upper layer!\n",
>>                       t, event, ts->resp, ts->stat));
>>               pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
>>       } else if (t->uldd_task) {
>> -             spin_unlock_irqrestore(&t->task_state_lock, flags);
>> +             spin_unlock_irq(&t->task_state_lock);
>>               pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
>>               mb();/* ditto */
>> -             spin_unlock_irqrestore(&pm8001_ha->lock, flags);
>> +             spin_unlock_irq(&pm8001_ha->lock);
>>               t->task_done(t);
>> -             spin_lock_irqsave(&pm8001_ha->lock, flags);
>> +             spin_lock_irq(&pm8001_ha->lock);
>>       } else if (!t->uldd_task) {
>> -             spin_unlock_irqrestore(&t->task_state_lock, flags);
>> +             spin_unlock_irq(&t->task_state_lock);
>>               pm8001_ccb_task_free(pm8001_ha, t, ccb, tag);
>>               mb();/*ditto*/
>> -             spin_unlock_irqrestore(&pm8001_ha->lock, flags);
>> +             spin_unlock_irq(&pm8001_ha->lock);
>>               t->task_done(t);
>> -             spin_lock_irqsave(&pm8001_ha->lock, flags);
>> +             spin_lock_irq(&pm8001_ha->lock);
>>       }
>> }
>
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