Re: New USB stack on FreeBSD w/Linux emulation layer coming

Am Montag, 21. Mai 2007 23:36 schrieb David Brownell:
> On Monday 21 May 2007, Oliver Neukum wrote:
> > Am Mittwoch, 16. Mai 2007 16:41 schrieb David Brownell:
> > > > in that when you have  
> > > > pre-allocated all buffers and all USB host controller descriptors, you will 
> > > > never get in the situation of not being able to allocate transfer descriptors 
> > > > on the fly, like done on Linux.
> > > 
> > > That's not a failure mode that's been often observed on Linux.  (Never,
> > > in my own experience... which I admit has not focussed on that particular
> > > type of stress load.)  So it's hard to argue that it should motivate a
> > > redesign of core APIs.
> > 
> > We are seeing report of the networking stack exhausting the atomic
> > pool. They are rare these days, but do exist.
> 
> But transfer descriptors don't come from there.

Never, ever, even if the pool is exhausted?

static struct uhci_td *uhci_alloc_td(struct uhci_hcd *uhci)
{
	dma_addr_t dma_handle;
	struct uhci_td *td;

	td = dma_pool_alloc(uhci->td_pool, GFP_ATOMIC, &dma_handle);
	if (!td)
		return NULL;

Admittedly unlikely, but impossible?

	Regards
		Oliver

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