[ofw] RE: Release IBA resources in DISPATCH_LEVEL ?

[Leonid Keller]

> The only reason waiting is needed is because the driver implementation
forces it.
Generally, you are right, but it's a bit more complicated then that. 
There are dependencies between the commands, which can cause problems in
fully asynchronous work with the card.
E.g., destroy_qp and destroy_cq: you have to check in driver whether you
may issue destroy_cq or you have to delay it till the completion of a
destroy_qp, which is still in the air.
That's why in Linux HCA drivers the command interface is also
synchronous.

> -----Original Message-----
> From: ofw-bounces at lists.openfabrics.org 
> [mailto:ofw-bounces at lists.openfabrics.org] On Behalf Of Fab Tillier
> Sent: Friday, June 13, 2008 12:28 AM
> To: Tzachi Dar; Sean Hefty; James Yang; ofw at lists.openfabrics.org
> Subject: RE: [ofw] RE: Release IBA resources in DISPATCH_LEVEL ?
> 
> > From: Tzachi Dar [mailto:tzachid at mellanox.co.il]
> > Sent: Thursday, June 12, 2008 2:22 PM
> >
> > If the user has to wait until the task is completed then we 
> are in a 
> > big trouble in any case.
> >
> > Releasing this resources means going to the command 
> interface and this 
> > means waiting for the HW in DPC level. This breaks the 
> entire module, 
> > and I hope that this is not how things are.
> 
> There is no waiting required - the HW will generate an 
> interrupt, which will queue the HCA driver's DPC, which will 
> invoke a callback.  The only reason waiting is needed is 
> because the driver implementation forces it.
> 
> So fixing the driver stack properly would require a new HCA 
> driver design, and appropriate changes to modules higher in 
> the stack.  That's a lot of work.
> 
> -Fab
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> ofw at lists.openfabrics.org
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> 


--
Leonid Keller
Mellanox Technologies LTD.
SW- Windows
Phone: +972 (4) 909 7200 (ext 372)
Mobile: +972 (54) 464 7702
E-mail: leonid at mellanox.co.il

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