On Mon, 23 Jul 2012, Glauber Costa wrote: > >> worth including unconditionally. Furthermore, the size related checks > >> certainly make sense and I don't see any harm in having them as well. > > > > There is a WARN_ON() there and then it returns NULL!!! Crazy. Causes a > > NULL pointer dereference later in the caller? > > > > It obviously depends on the caller.
This is a violation of the calling convention to say the least. This means if you have SLAB_PANIC set and accidentally set the name to NULL the function will return despite the error and not panic! > Although most of the calls to kmem_cache_create are made from static > data, we can't assume that. Of course whoever is using static data > should do those very same tests from the outside to be safe, but in case > they do not, this seems to fall in the category of things that make > debugging easier - even if we later on get to a NULL pointer dereference. > > Your mentioned bias towards minimum code size, however, is totally > valid, IMHO. But I doubt those checks would introduce a huge footprint. > I would imagine you being much more concerned about being able to wipe > out entire subsystems like memcg, which will give you a lot more. They are useless checks since any use of the name will also cause a NULL pointer dereference. Same is true for interrupt checks. Checks like that indicate a deterioration of the code base. People are afraid that something goes wrong because they no longer understand the code so they build a embroidery around it instead of relying on the already existing checks at vital places. The embroidery can be useful for debugging thats why I left it in for the CONFIG_DEBUG_VM but certainly should not be included in production kernels. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
