Re: panic in 8-CURRENT

Hiroki Sato wrote:
> Hiroki Sato <hrs_at_freebsd.org> wrote
>   in <20071019.021408.138664034.hrs_at_allbsd.org>:
>
> hr> Hiroki Sato <hrs_at_FreeBSD.org> wrote
> hr>   in <20071015.034121.120532311.hrs_at_allbsd.org>:
> hr>
> hr> hr> I got the following panic with the Oct 14 8-CURRENT kernel.  A 2-way
> hr> hr> (Opteron) box running GENERIC FreeBSD/i386 kernel with serial console
> hr> hr> access, and typing some keys just after "Trying to mount..." line
> hr> hr> appears seems to prevent this panic.  Without typing any keys the box
> hr> hr> remain stopped after displaying the line, and then typing a key will
> hr> hr> cause this panic.  Whether the panic occurs depends on the time
> hr> hr> between displaying the line and typing a key.
> hr> hr>
> hr> hr> ----(from here)
> hr> hr> WARNING: WITNESS option enabled, expect reduced performance.
> hr> hr> Trying to mount root from ufs:/dev/ad4s1a
> hr> hr> spin lock 0xc0c17a6c (sio) held by 0xc3f0d630 (tid 100004) too long
> hr> hr> panic: spin lock held too long
> hr> hr> cpuid = 0
> hr> hr> KDB: enter: panic
> hr> hr> [thread pid 46 tid 100056 ]
> hr> hr> Stopped at      kdb_enter+0x32: leave
> (snip)
>
> hr>  I found that this panic occurred only when "options [KDG]DB" were
> hr>  defined and reproducible on serial-console-enabled HP boxes such as
> hr>  DL140G3 and ML115.  With the options, the same panic occurs even on
> hr>  6.2R.
>
>  After some investigation, I found it occurs only when options
>  BREAK_TO_DEBUGGER (or ALT_BREAK_TO_DEBUGGER) is defined.  More
>  specifically, the box stops if the following line exists in sio.c:
>
>  |#if defined(KDB) && (defined(BREAK_TO_DEBUGGER) || \
>  |    defined(ALT_BREAK_TO_DEBUGGER))
>  |                /*
>  |                 * Enable interrupts for early break-to-debugger support
>  |                 * on the console.
>  |                 */
>  |                if (ret == 0 && unit == comconsole)
>  |                        outb(siocniobase + com_ier, IER_ERXRDY | IER_ERLS |
>  |                            IER_EMSC);
>  |#endif
>
>  If this line is removed, no hiccup just after "Trying to mount
>  root..." and no panic occur.  I guess enabling sio's interrupt
>  this early stage causes a deadlock, but I am not sure the details of
>  what happends there.
>
>  Anyone who can reproduce this problem?
>
> --
> | Hiroki SATO
>   
I can reproduce it at will on 7.0-BETA1 on my HP Pavillion dv9420us.  I
have to do the <spacebar> shuffle every time in order to boot.  I'm
going to try your patch and see if it helps.  I note that I don't have
sio installed as this laptop has no serial ports (just lots of usb ports).

jmc