From: Jens Axboe <axboe@kernel.dk>
To: "Linus Torvalds" <torvalds@linux-foundation.org>,
"Pali Rohár" <pali@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: pktcdvd
Date: Sun, 29 Jan 2023 14:53:41 -0700 [thread overview]
Message-ID: <f8bac3d8-4167-f9cc-5549-ff87a27f2155@kernel.dk> (raw)
In-Reply-To: <CAHk-=whfor49J0YTYi6zauiJ_MWwF-XwhSty+HvD4CzxFQ_ZGA@mail.gmail.com>
On 1/28/23 12:43 PM, Linus Torvalds wrote:
> 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.
To be fair, this code is 20 years old... It should not be using
BUG_ON(), totally agree, but that it was quite common back in those
days.
--
Jens Axboe
next prev parent reply other threads:[~2023-01-29 21:54 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 ` pktcdvd Linus Torvalds
2023-01-29 21:53 ` Jens Axboe [this message]
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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