On Wed, Sep 8, 2021 at 10:16 AM Shuah Khan [off-list ref] wrote:

On 9/8/21 11:05 AM, Arnd Bergmann wrote:

quoted

On Wed, Sep 8, 2021 at 4:12 PM Shuah Khan [off-list ref] wrote:

quoted

On 9/7/21 5:14 PM, Linus Torvalds wrote:

quoted

The KUNIT macros create all these individually reasonably small
initialized structures on stack, and when you have more than a small
handful of them the KUNIT infrastructure just makes the stack space
explode. Sometimes the compiler will be able to re-use the stack
slots, but it seems to be an iffy proposition to depend on it - it
seems to be a combination of luck and various config options.

I have been concerned about these macros creeping in for a while.
I will take a closer look and work with Brendan to come with a plan
to address it.

I've previously sent patches to turn off the structleak plugin for
any kunit test file to work around this, but only a few of those patches
got merged and new files have been added since. It would
definitely help to come up with a proper fix, but my structleak-disable
hack should be sufficient as a quick fix.

Looks like these are RFC patches and the discussion went cold. Let's pick
this back up and we can make progress.

https://lore.kernel.org/lkml/CAFd5g45+JqKDqewqz2oZtnphA-_0w62FdSTkRs43K_NJUgnLBg@mail.gmail.com/ (local)

I can try to get the patch reapplying and send it out (I just figured
that Arnd or Kees would want to send it out :-)  since it was your
idea).

I definitely agree that in the cases where KUnit is not actually
contributing to blowing the stack - struct leak just thinks it is,
this is fine; however, it sounds like Linus' concerns with KUnit's
macros go deeper than this. Arnd, I think you sketched out a way to
make the KUNIT_* macros take up less space, but after some
investigation we found that it was pretty inflexible.

Ideally test cases should never get big enough for KUNIT_* macros to
be a problem (when they do it is usually an indication that your test
case is trying to do too many things); nevertheless, we are still in
this situation.

I think I will need to dust off some cobwebs out of my brain to
remember why I didn't like the idea of making the KUNIT_* macros take
up less stack space.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel