From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Pali Rohár" <pali@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: pktcdvd
Date: Sat, 28 Jan 2023 11:43:46 -0800 [thread overview]
Message-ID: <CAHk-=whfor49J0YTYi6zauiJ_MWwF-XwhSty+HvD4CzxFQ_ZGA@mail.gmail.com> (raw)
In-Reply-To: <20230128193458.ukl35ev4mwbjmu6b@pali>
On Sat, Jan 28, 2023 at 11:35 AM Pali Rohár <pali@kernel.org> wrote:
>
> Hello! Sorry for a longer delay. Now I have started testing it with
> Linux 6.2.0-rc5. Adding mapping works fine. Reading also works. Mounting
> filesystem also works, reading mounted fs also. But after writing some
> data to fs and calling sync cause kernel oops. Below is the dmesg log.
> "sync" freezes and never finish.
>
> [ 1284.701497] pktcdvd: pktcdvd0: writer mapped to sr0
> [ 1321.432589] pktcdvd: pktcdvd0: Fixed packets, 32 blocks, Mode-2 disc
> [ 1321.437543] pktcdvd: pktcdvd0: maximum media speed: 10
> [ 1321.437546] pktcdvd: pktcdvd0: write speed 10x
> [ 1327.098955] pktcdvd: pktcdvd0: 590528kB available on disc
> [ 1329.737263] UDF-fs: INFO Mounting volume 'LinuxUDF', timestamp 2023/01/28 19:16 (103c)
> [ 1435.627449] ------------[ cut here ]------------
> [ 1435.627466] kernel BUG at drivers/block/pktcdvd.c:2434!
Well, this is very much an example of one of the BUG_ON() cases I
absolutely hate - not only did it cause the traceback (which can be
interesting), it also effectively killed the machine in the process.
So that BUG_ON() most definitely shouldn't be a BUG_ON().
Turning it into a WARN_ON() (possibly even of the "ONCE" variety)
together with then finishing the IO with a bio_io_error() would have
been a better option for debugging.
Of course, the real fix is to fix whatever causes it, and I don't know
what that is.
So I'm just piping up to once more highlight my hatred of using
BUG_ON() for "this shouldn't happen" debug code. It's basically never
the right thing to do unless you are in core code that would kill the
machine anyway.
Linus
next prev parent reply other threads:[~2023-01-28 19:44 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-25 22:07 Linux 6.2-rc1 Linus Torvalds
2022-12-26 19:52 ` Guenter Roeck
2022-12-26 20:56 ` Linus Torvalds
2022-12-26 21:03 ` Kees Cook
2022-12-26 22:10 ` Guenter Roeck
2022-12-27 0:29 ` Guenter Roeck
2022-12-27 1:32 ` Kees Cook
2022-12-27 5:52 ` Guenter Roeck
2022-12-28 3:40 ` Kees Cook
2022-12-28 14:44 ` Guenter Roeck
2023-01-07 0:06 ` Jaegeuk Kim
2022-12-26 22:41 ` Vlastimil Babka
2022-12-26 21:10 ` Max Filippov
2022-12-26 22:08 ` Guenter Roeck
2022-12-27 8:29 ` Build regressions/improvements in v6.2-rc1 Geert Uytterhoeven
2022-12-27 8:35 ` Geert Uytterhoeven
2023-01-01 1:33 ` Rob Landley
2023-01-01 12:24 ` Geert Uytterhoeven
2023-01-04 6:32 ` Michael Ellerman
2023-01-06 15:10 ` John Paul Adrian Glaubitz
2023-01-06 15:17 ` Geert Uytterhoeven
2023-01-06 15:18 ` Geert Uytterhoeven
2023-01-17 16:42 ` Calculating array sizes in C - was: " John Paul Adrian Glaubitz
2023-01-17 17:01 ` Geert Uytterhoeven
2023-01-17 17:06 ` John Paul Adrian Glaubitz
2023-01-17 20:05 ` Geert Uytterhoeven
2023-01-17 20:37 ` John Paul Adrian Glaubitz
2023-01-19 22:11 ` Michael.Karcher
2023-01-20 3:31 ` Rob Landley
2023-01-20 10:53 ` Segher Boessenkool
2023-01-20 18:29 ` Michael.Karcher
2023-01-20 8:49 ` John Paul Adrian Glaubitz
2023-01-20 19:29 ` Michael Karcher
2023-01-21 21:26 ` John Paul Adrian Glaubitz
2023-01-06 15:39 ` Alex Deucher
2023-01-04 19:01 ` Linux 6.2-rc1 Pali Rohár
2023-01-04 19:25 ` Linus Torvalds
2023-01-04 20:56 ` Pali Rohár
2023-01-04 21:27 ` Pali Rohár
2023-01-04 21:32 ` Linus Torvalds
2023-01-04 21:43 ` Jens Axboe
2023-01-05 11:25 ` Greg Kroah-Hartman
2023-01-05 15:26 ` Jens Axboe
2023-01-05 17:42 ` Pali Rohár
2023-01-05 17:45 ` Jens Axboe
2023-01-05 19:06 ` Linus Torvalds
2023-01-05 19:22 ` Pali Rohár
2023-01-05 19:40 ` Jens Axboe
2023-01-05 20:03 ` Linus Torvalds
2023-01-05 20:33 ` Jens Axboe
2023-01-06 16:58 ` Pali Rohár
2023-01-06 17:04 ` Jens Axboe
2023-01-28 19:34 ` pktcdvd Pali Rohár
2023-01-28 19:43 ` Linus Torvalds [this message]
2023-01-29 21:53 ` pktcdvd Jens Axboe
2023-01-29 21:55 ` pktcdvd Jens Axboe
2023-01-29 22:21 ` pktcdvd Pali Rohár
2023-01-29 22:34 ` pktcdvd Jens Axboe
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