Driver patch to look at...

[Randall Stewart]

Hmm

That would trade off a stack pointer + a compare
vs always doing the move.

Thats fine until I have to add the _mc() version, then the put
back would be an atomic, and most of the time the return from
this is probably not changed…

I really would prefer not to since the compare and maybe store vs
the always store.. though the same now, would be far more expensive
in the _mc version.. if we do a _mc version of course ;-)

But I am willing to do whatever .. since this really needs to be fixed.

R
On Feb 5, 2013, at 1:52 PM, John Baldwin wrote:

> On Tuesday, February 05, 2013 12:44:01 pm Randall Stewart wrote:
>> Actually, no it is used.
>> 
>> If you look in if_var.h int he drbr_putback() function, it does
>> a buf_ring_swap when the old mbuf pointer does not equal the
>> new mbuf pointer. This *does* happen, I crashed at least once
>> yesterday when the igb driver did something to free the original
>> mbuf and return a new mbuf with the data (prepend or some such).
>> 
>> I also have found several issues that I have fixed this morning.. its been
>> crash city on my test beds..
>> 
>> Here is the latest patch with all fixes and suggested changes from emaste 
> (thanks Ed)
> 
> Actually, one more suggestion then (since you have to keep putback).  It
> would be nice to not have to require 'snext' in all the callers.  How
> about replace buf_ring_swap() with a buf_ring_putback_sc() that accepts the
> mbuf and just stores it at the head unconditionally and have drbr_putback()
> use that?
> 
> -- 
> John Baldwin
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------------------------------
Randall Stewart
803-317-4952 (cell)