svn commit: r332957 - head/sys/kern

[Mateusz Guzik]

On Tue, Apr 24, 2018 at 8:41 PM, Conrad Meyer <cem at freebsd.org> wrote:

> Author: cem
> Date: Tue Apr 24 18:41:14 2018
> New Revision: 332957
> URL: https://svnweb.freebsd.org/changeset/base/332957
>
> Log:
>   lockmgr: Add missed neutering during panic
>
>   r313683 introduced new lockmgr APIs that missed the panic-time neutering
>   present in the rest of our locks.  Correct that by adding the usual
> check.
>
>   Additionally, move the __lockmgr_args neutering above the assertions at
> the
>   top of the function.  Drop the interlock unlock because we shouldn't have
>   an unneutered interlock either.  No point trying to unlock it.
>
>   PR:           227749
>   Reported by:  jtl
>   Sponsored by: Dell EMC Isilon
>
> Modified:
>   head/sys/kern/kern_lock.c
>
> Modified: head/sys/kern/kern_lock.c
> ============================================================
> ==================
> --- head/sys/kern/kern_lock.c   Tue Apr 24 18:19:30 2018        (r332956)
> +++ head/sys/kern/kern_lock.c   Tue Apr 24 18:41:14 2018        (r332957)
> @@ -918,6 +918,9 @@ lockmgr_lock_fast_path(struct lock *lk, u_int flags, s
>         u_int op;
>         bool locked;
>
> +       if (__predict_false(panicstr != NULL))
> +               return (0);
> +
>
>
This only further pollutes the slowpath. I mean fastpath. All the fallback
funcs check for panic, so there is no need to do it in regular kernels at
this level.

Instead, the firing assertion should also see if perhaps the kernel
already has panicked.

Alternatively, the checks added here can be conditional on INVARIANTS.

-- 
Mateusz Guzik <mjguzik gmail.com>