Re: The pm80xx driver hangs in 3.10 with the Adaptec 71605H HBA

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi Anand,

On 07/12/2013 03:14 PM, Anand Kumar Santhanam wrote:
> Hans,
> 
> I reviewed the code changes and I did not see major differences except
> for the fact that in adaptec driver we have 64 interrupt handlers to
> handle 64 MSI-X.
> This was optimized in open src driver to use only 1 interrupt handler.
> Can you pls make this change to the open src driver (i.e have multiple
> interrupt handlers for multiple MSI-X) and check?

I've looked at this more closely, and I wonder whether there isn't a race condition
here. When an interrupt arrives you put the interrupt vector in pm8001_ha->int_vector,
then schedule the tasklet. But what if two interrupts with different vectors arrive
in quick succession before the tasklet got a chance to run? In that case the tasklet
will only see the second vector, not the first. Rather scary.

I have not actually seen any issues with this, but by definition race conditions are
hard to reproduce and I haven't done any serious testing with this card. For now I
will run with the quick and dirty msi.diff (http://hverkuil.home.xs4all.nl/msi.diff).

I see two solutions: either use the 64 interrupt handlers as done in the adaptec
driver, or you can change int_vector into a u64 and use it as a bitmask to record
all interrupt vectors that have arrived.

BTW, another difference between the linux kernel driver and the adaptec version are
several of the defines in pm8001_defs.h: e.g. MPI_QUEUE is 256 in the adaptec driver,
while it is 1024 in the kernel driver. There are other differences as well.

Are all the changes in the kernel correct? I would like to have a confirmation of
that before I am going to trust my data to this driver.

It clearly hasn't been tested with actual hardware :-(

Regards,

	Hans