On 01/27/2016 01:59 AM, Joonsoo Kim wrote: > On Tue, Jan 26, 2016 at 04:36:11PM -0800, David Rientjes wrote: >> On Wed, 27 Jan 2016, Joonsoo Kim wrote: >> >>>> I'd agree if CONFIG_DEBUG_PAGEALLOC only did anything when >>>> debug_pagealloc_enabled() is true, but that doesn't seem to be the case. >>>> When CONFIG_DEBUG_SLAB is enabled, for instance, CONFIG_DEBUG_PAGEALLOC >>>> also enables stackinfo storing and poisoning and it's not guarded by >>>> debug_pagealloc_enabled(). >>>> >>>> It seems like CONFIG_DEBUG_PAGEALLOC enables debugging functionality >>>> outside the scope of the debug_pagealloc=on kernel parameter, so >>>> DEBUG_PAGEALLOC(disabled) actually does mean something. >>> >>> Hello, David. >>> >>> I tried to fix CONFIG_DEBUG_SLAB case on 04/16 of following patchset. >>> >>> http://thread.gmane.org/gmane.linux.kernel.mm/144527 >>> >>> I found that there are more sites to fix but not so many. >>> We can do it. >>> >> >> For the slab case, sure, this can be fixed, but there is other code that >> uses CONFIG_DEBUG_PAGEALLOC to suggest debugging is always enabled and is >> indifferent to debug_pagealloc_enabled(). I find this in powerpc and >> sparc arch code as well as generic vmalloc code. > > Yes, I also found it. > >> >> If we can convert existing users that only check for >> CONFIG_DEBUG_PAGEALLOC to rather check for debug_pagealloc_enabled() and >> agree that it is only enabled for debug_pagealloc=on, then this would seem >> fine. However, I think we should at least consult with those users before >> removing an artifact from the kernel log that could be useful in debugging >> why a particular BUG() happened. > > Yes, at least, non-architecture dependent code (vmalloc, SLAB, SLUB) should > be changed first. If Christian doesn't mind, I will try to fix above 3 > things. Ok. So I will change this as Heiko and Thomas suggested for s390 and x86 and resend these 3 patches. Feel free to work on the other areas. Christian -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>