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From: | Linus Torvalds |
Subject: | Re: [Qemu-devel] [PATCH 1/7] userfaultfd: require UFFDIO_API before other ioctls |
Date: | Mon, 15 Jun 2015 11:55:38 -1000 |
On Jun 15, 2015 11:43 AM, "Andrea Arcangeli" <address@hidden> wrote:
>
> Several times I got very hardly reproducible bugs noticed purely
> because of BUG_ON (not VM_BUG_ON)
Feel free to use them while developing. Don't send me patches with your broken debug code, though.
For users, a dead machine means that it is less likely you will ever get a bug report. People set "reboot on oops", and when running X is not always something that can be seen anyway. They'll just see a rebooting or a dead machine, and not send you any debug output.
This is not negotiable. Seriously. Get rid of the BUG_ON if you expect your patches to be merged mainline.
Also, even for debugging, using something like
if (WARN_ON_ONCE(...))
return -EINVAL;
is the right thing to do. Then you can unwind locks etc, and return cleanly, and you'll only get one warning rather than a stream of them etc.
So stop making excuses for your bad BUG_ON use. Do it in private where nobody can see your perversions, or do it right.
Linus
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