Thanks Jack for your response.
'process_oq' is called at two places.
pm8001_8001_dispatch = {
.......
.isr = pm8001_chip_isr --> process_oq, // 1st place
.isr_process_oq = process_oq, //
2nd place
.....
}
regards
santosh
On Mon, Feb 27, 2012 at 10:18 AM, Jack Wang <jack_wang@xxxxxxxxx> wrote:
> Infact , process_oq is only called in pm8001_chip_isr, but this patch looks
> OK for me. Move down the lock to process_oq is OK.
>
> Thanks for fix.
> Acked-by : Jack Wang <jack_wang@xxxxxxxxx>
>
>> From: Santosh Nayak <santoshprasadnayak@xxxxxxxxx>
>>
>> There is a possble racing scenario.
>>
>> 'process_oq' is called by two routines, as shown below.
>>
>> pm8001_8001_dispatch = {
>> .......
>>
>> .isr = pm8001_chip_isr --> process_oq,// A
>> .isr_process_oq = process_oq, // B
>> .....
>> }
>>
>> process_oq() --> process_one_iomb() --> mpi_sata_completion()
>>
>> In 'mpi_sata_completion', "pm8001_ha->lock" is first released.
>> It means lock is taken before, which is true for
>> the context A, as 'pm8001_ha->lock' is taken in 'pm8001_chip_isr()'
>>
>> But for context B there is no lock taken before and pm8001_ha->lock
>> is unlocked in 'mpi_sata_completion()'. This may unlock the lock
>> taken in context A. Possible racing ??
>>
>> If 'pm8001_ha->lock' is taken in 'process_oq()' instead of
>> 'pm8001_chip_isr' then the above issue can be avoided.
>>
>> Signed-off-by: Santosh Nayak <santoshprasadnayak@xxxxxxxxx>
>> ---
>> drivers/scsi/pm8001/pm8001_hwi.c | 6 +++---
>> 1 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/scsi/pm8001/pm8001_hwi.c
>> b/drivers/scsi/pm8001/pm8001_hwi.c
>> index 838e3e2..6d9973b 100644
>> --- a/drivers/scsi/pm8001/pm8001_hwi.c
>> +++ b/drivers/scsi/pm8001/pm8001_hwi.c
>> @@ -3663,7 +3663,9 @@ static int process_oq(struct pm8001_hba_info
> *pm8001_ha)
>> void *pMsg1 = NULL;
>> u8 uninitialized_var(bc);
>> u32 ret = MPI_IO_STATUS_FAIL;
>> + unsigned long flags;
>>
>> + spin_lock_irqsave(&pm8001_ha->lock, flags);
>> circularQ = &pm8001_ha->outbnd_q_tbl[0];
>> do {
>> ret = mpi_msg_consume(pm8001_ha, circularQ, &pMsg1, &bc);
>> @@ -3682,6 +3684,7 @@ static int process_oq(struct pm8001_hba_info
> *pm8001_ha)
>> break;
>> }
>> } while (1);
>> + spin_unlock_irqrestore(&pm8001_ha->lock, flags);
>> return ret;
>> }
>>
>> @@ -4087,12 +4090,9 @@ static u32 pm8001_chip_is_our_interupt(struct
>> pm8001_hba_info *pm8001_ha)
>> static irqreturn_t
>> pm8001_chip_isr(struct pm8001_hba_info *pm8001_ha)
>> {
>> - unsigned long flags;
>> - spin_lock_irqsave(&pm8001_ha->lock, flags);
>> pm8001_chip_interrupt_disable(pm8001_ha);
>> process_oq(pm8001_ha);
>> pm8001_chip_interrupt_enable(pm8001_ha);
>> - spin_unlock_irqrestore(&pm8001_ha->lock, flags);
>> return IRQ_HANDLED;
>> }
>>
>> --
>> 1.7.4.4
>>
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