Re: [PATCH] RDMA/cxgb4: Unblock reads on comp_channel

[Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

On 10/20/2011 12:25 PM, Parav.Pandit-iH1Dq9VlAzfQT0dZR+AlfA@public.gmane.org wrote:
> You are right, cq_lock will result into dead lock.
> Should there be a additional compl_handler spin_lock?
> I was measuring performance impact for adding it, and, irq_save() and irq_restore() variant showed additional 200 cycles, which I believe should be o.k.?
>
> Parav
>

Yea, I think adding a comp_handler spin lock would do the trick.  I'll let Kumar come up with this change.



> -----Original Message-----
> From: Steve Wise [mailto:swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org]
> Sent: Thursday, October 20, 2011 9:52 PM
> To: Roland Dreier
> Cc: Pandit, Parav; kumaras-ut6Up61K2wZBDgjK7y7TUQ@public.gmane.org; linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; divy-ut6Up61K2wZBDgjK7y7TUQ@public.gmane.org
> Subject: Re: [PATCH] RDMA/cxgb4: Unblock reads on comp_channel
>
> On 10/20/2011 11:06 AM, Roland Dreier wrote:
>> On Thu, Oct 20, 2011 at 2:11 AM,<Parav.Pandit-laKkSmNT4hbQT0dZR+AlfA@public.gmane.org>   wrote:
>>> http://lxr.linux.no/#linux+v3.0.4/Documentation/infiniband/core_locking.txt
>>>
>>> Line no 66 to 97 states that - at a given point of time, there should be only one callback per CQ should be active.
>>> Is this ensured?
>>>
>>> compl_handler() is invoked from multiple places flush_qp() and post_qp_event() to my mind.
>> Yes, does look like an issue with this patch :(
>>
> And I think this bug exists in the T3 driver too.
>

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