On Friday, May 30, 2014 11:39:24 am Attilio Rao wrote: > On Fri, May 30, 2014 at 5:03 PM, John Baldwin <j...@freebsd.org> wrote: > > On Friday, May 30, 2014 10:54:06 am Attilio Rao wrote: > >> On Tue, May 27, 2014 at 11:31 PM, Scott Long <sco...@freebsd.org> wrote: > >> > Author: scottl > >> > Date: Tue May 27 21:31:11 2014 > >> > New Revision: 266775 > >> > URL: http://svnweb.freebsd.org/changeset/base/266775 > >> > > >> > Log: > >> > Eliminate the fake contig_dmamap and replace it with a new flag, > >> > BUS_DMA_KMEM_ALLOC. They serve the same purpose, but using the flag > >> > means that the map can be NULL again, which in turn enables significant > >> > optimizations for the common case of no bouncing. > >> > >> While I think this is in general a good idea, unfortunately our > >> drivers do so many dumb things when freeing DMA allocated buffers that > >> having a NULL map is going to cause some "turbolence" and make such > >> bugs more visible. > >> An example is with ATA, where I think this fix is needed: > >> http://www.freebsd.org/~attilio/dmamem_free-ata.patch > >> > >> Otherwise, what can happen with bounce buffers, is that the allocated > >> memory via contig malloc was not going to be freed anytime. > >> > >> I tried to look around and I found questionable (read broken) code in > >> basically every driver which allocates DMA buffers, so I really don't > >> feel I want to fix the majority of our drivers. I just think such > >> paths are not excercised enough to be seen in practice often or the > >> bugs just get unnoticed. > > > > Eh, many maps for static allocations were already NULL and have been for a > > long time. This is nothign new. Plus, the diff you posted has a bug > > regardless of explicitly destroying a map created by bus_dmamem_alloc(). > > Did you notice that I *removed* the destroy not *added*?
Yes, my point was that that bug in the original code you are fixing was there regardless of Scott's change. -- John Baldwin _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
