[LTP] [PATCH] madvise07: Increase probability of testing a supported page type

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> We were attempting to poison page types which do not support it (e.g. the
> zero
> page) due to our usage of mmap. Now we map some anonymous memory and write to
> it. Hopefully ensuring the underlying page is of a supported type.
> + * If the underlying page type of the memory we have mapped does not support
> + * poisoning then the test will fail. We try to map and write to the memory
> in
> + * such a way that by the time madvise is called the virtual memory address
> + * points to a supported page. However there may be some rare circumstances
> + * where the test produces the wrong result because we have somehow obtained
> + * an unsupported page.

Hi,

Can you elaborate please? If we always do mmap+touch anonymous memory,
how would we sometime end up with different page type?

I don't have objections to patch, but I'm thinking if we should go
further if there's possibility the test still won't be reliable.
We could relax the condition, for example by FAILing only if
child dies unexpectedly (signal != SIGBUS).

Regards,
Jan