On 08/13/2014 04:33 PM, Anish Bhatt wrote:
Adding Casey who's actually incharge of this code and missing from the CC list
Thanks Anish!
As I mentioned to Anish, there are fundamentally two problems here in
the time being consumed by the cxgb4 PCI probe() function:
1. When various firmware files aren't present, request_firmware()
can take a very long time. This is easily solved by using
request_firmware_direct() and I certainly have no objection to that.
2. When there are multiple adapters present in a system which
need firmware downloaded, each one individually may not take
a ton of time but together they can exceed simple Module Load
Timeouts. There's not a simple answer here.
Part of the problem here is that it's a Module Load Timeout instead
of a per-device Probe Timeout. Part of the problem is that the current
architecture has Device Probe happening out of the Module Initialization
when we call pci_register_driver() with our PCI Device ID Table.
Running the Device Probes asynchronously has been discussed but that
has the problem that it's then impossible to return the Device Probe
Status. This is a problem for Driver Fallback and, if the probe fails,
we're not supposed to call the Device Remove function. To make this
work, the synchronous/asynchronous boundary would really need to be up
in the PCI Infrastructure layer so the Device Probe status could be
captured in the normal logic. This would be a moderately large change
there ...
Deferring the Device Initialization till the first "ifup" has also
been discussed and is certainly possible, though a moderately large
architectural change to every driver which needs it. It also has the
unfortunate effect of introducing random large delays directly on user
commands. From a User Experience perspective I would tend to want such
large delays in the Device Probe. But that's something that really
deserves a real User Interaction study rather than throwing a dart.
On the whole, I think that introducing these Module Load Timeouts
hasn't been well thought out with respect to the repercussions and I'd
be more inclined to back that out till a well thought out design is
developed. But I'm here for the discussion.
Casey
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