On Fri, Jun 10, 2011 at 03:01:15PM -0700, David Rientjes wrote: > On Fri, 10 Jun 2011, Russell King - ARM Linux wrote: > > See Linus' reply. I quote again "on platforms where it doesn't matter it > > should be a no-op". If _you_ have a problem with that _you_ need to > > discuss it with _Linus_, not me. I'm not going to be a middle-man sitting > > between two people with different opinions. > > We're talking about two different things. Linus is saying that if GFP_DMA > should be a no-op if the hardware doesn't require DMA memory because the > kernel was correctly compiled without CONFIG_ZONE_DMA. I'm asking about a > kernel that was incorrectly compiled without CONFIG_ZONE_DMA and now we're > returning memory from anywhere even though we actually require GFP_DMA. How do you distinguish between the two states? Answer: you can't. > If you don't want to form an opinion of your own, then I have no problem > cc'ing Linus on it. I think I've made my position in this fairly clear with our previous discussions on this. The fact of the matter is that there are some drivers which use GFP_DMA because they need that on _some_ platforms but not all. Not all platforms are _broken_ with respect to DMA, and those which aren't broken don't provide a DMA zone. Therefore, it is _perfectly_ _legal_ to honor a GFP_DMA allocation on a kernel without CONFIG_ZONE_DMA set. That position appears to be reflected by Linus' response, so > I don't think he'd object to a > > #ifndef CONFIG_ZONE_DMA > WARN_ON_ONCE(1, "%s (%d): allocating DMA memory without DMA support -- " > "enable CONFIG_ZONE_DMA if needed.\n", > current->comm, current->pid); > #endif I think he will definitely object to this on the grounds that its adding useless noise for conditions which are _perfectly_ _valid_. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>