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. 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. -- 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>