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Re: workqueue in if_bnx: static struct work * seems wrong
On Friday 02 March 2012 10:00:44 Manuel Bouyer wrote:
> On Fri, Mar 02, 2012 at 09:57:00AM -0700, Sverre Froyen wrote:
> > Sorry, I was following up to the latest message on the thread and doing a
> > poor job of quoting.
> > I was really thinking about the change that prompted this discussion
> > (if_bnx.c rev 1.44). In particular the replacement of
> > bnx_alloc_pkts(sc)
> > with
> > workqueue_enqueue(sc->bnx_wq, &bnx_wk, NULL);
> > SET(sc->bnx_flags, BNX_ALLOC_PKTS_FLAG);
> > which was made in order to avoid memory allocation in interrupt context.
> > It seems to me that this could be handled by the pool code instead.
> > Perhaps as follows:
> > 1) Create pool_caches of header structures (one per buffer size).
> > 2) Use a custom allocator that does the bus_dma dance and attaches the
> > resulting memory pointers to the header structure.
> The problem is actually in bus_dma, so using pool_cache here won't help.
> The problematic bus_dma routine (I don't remmeber which one, sorry) could
> still be called from interrupt context.
It's bus_dmamem_map which is using a pool with IPL_NONE. This is one of the
issues I was referring to. I think the trick might be to
1) allow pool_cache_get to return existing items for an IPL_NONE cache even
when called in interrupt context (this will require changes to the pool /
pool_cache locking code).
2) fix the code that manages the low water mark so that it does not run in
interrupt context (perhaps use a separate thread to grow the pools).
The idea is that the low water mark would guarantee available buffers for the
drivers, most of the time.
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