pfind_locked(pid) fails when in a jail?

[Mateusz Guzik]

On Tue, Oct 17, 2017 at 12:24 AM, Rick Macklem <rmacklem at uoguelph.ca> wrote:

> Hi,
>
> A problem w.r.t. the NFSv4 client's renew thread (nfscl) running up a lot
> of CPU
> when the NFSv4 mount is in a jail has been reported to the freebsd-stable@
> mailing list.
>
> I know nothing about jails, but when looking at the code, the most obvious
> cause of this would be "pfind_locked(pid)" failing to find a process.
> - Will a jail affect how pfind_locked() behaves?
> - If the answer is "yes", then I need to know how to either...
>    1 - Make pfind_locked() work the same as when no jail exists.
>    OR
>    2 - A way for the Renew thread can determine that a jail will affect
> pfind_locked()
>      behaviour, so it can avoid this problem.
> #1 is preferred, since #2 may not be 100% correct, although #2 would allow
> the
> code to behave well for most cases. (The exception is a case where a file
> remains
> open for a long period of time, with different processes doing byte range
> locks on
> the file.)
>

pfind* does not do any filtering.

The real question though is why are you calling it in the first place. The
calls
I grepped in nfscl_procdoesntexist are highly suspicious - there is no
guarantee
the process you found here is the same you had at the time you were saving
the pid.

There is no usable process exit notification right now, but it can be added
if necessary.

-- 
Mateusz Guzik <mjguzik gmail.com>