Re: panic: biodone2 already

[Jaromír Doleček <jaromir.dolecek%gmail.com@localhost>]

This is always a bug, driver processes same buf twice. It can do harm.
If the buf is reused for some other I/O, system can fail to store
data, or claim to read data when it didn't.

Can you give full backtrace?

Jaromir

2018-08-06 17:56 GMT+02:00 Emmanuel Dreyfus <manu%netbsd.org@localhost>:
> Hello
>
> I have a Xen domU that now frequently panics with "biodone2 already". I
> suspect it started after upgrading to NetBSD 8.0.
>
> The offending code is in src/sys/kern/vfs_bio.c (see below). I wonder if
> we could not just release the mutex and exit in that case. Can it make
> some harm?
>
> static void
> biodone2(buf_t *bp)
> {
>         void (*callout)(buf_t *);
>
>         SDT_PROBE1(io, kernel, ,done, bp);
>
>         BIOHIST_FUNC(__func__);
>         BIOHIST_CALLARGS(biohist, "bp=%#jx", (uintptr_t)bp, 0, 0, 0);
>
>         mutex_enter(bp->b_objlock);
>         /* Note that the transfer is done. */
>         if (ISSET(bp->b_oflags, BO_DONE))
>                 panic("biodone2 already");
>
> Cou
>
> --
> Emmanuel Dreyfus
> http://hcpnet.free.fr/pubz
> manu%netbsd.org@localhost