Re: [PATCH] periodically scan redzone entries and slab controlstructures

[Andi Kleen]

Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> writes:

> The redzone words are only checked during alloc and free - thus objects
> that are never/rarely freed are not checked at all.
>
> The attached patch adds a periodic scan over all objects and checks for
> wrong redzone data or corrupted bufctl lists.
>
> Most changes are under #ifdef DEBUG, the only exception is a trivial
> correction for the initial timeout calculation: divide the cachep address
> by L1_CACHE_BYTES before the mod - the low order bits are always 0.

Very nice patch. One request: Can you global and EXPORT_SYMBOL
the scanning function?

There is a kernel testing technique called "thrashing" that relies
on doing some custom stress from a kernel module and then checking
all state very often to catch corruption early. Calling the slab check m
ore often from such a test module would be useful.

Also I would make the slab test interval a kernel parameter to 
force more regular checking during stress testing.

-Andi
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