From: Jens Axboe <axboe@kernel.dk>
To: Nicholas Piggin <npiggin@gmail.com>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH] powerpc: don't try to copy ppc for task with NULL pt_regs
Date: Mon, 27 Mar 2023 06:42:28 -0600 [thread overview]
Message-ID: <1052468e-6b4e-16f2-a87e-fb403f0725f6@kernel.dk> (raw)
In-Reply-To: <CRGYHQ3C77DV.1PXS812TV997N@bobo>
[-- Attachment #1: Type: text/plain, Size: 1277 bytes --]
On 3/27/23 12:36?AM, Nicholas Piggin wrote:
> On Mon Mar 27, 2023 at 8:15 AM AEST, Jens Axboe wrote:
>> Powerpc sets up PF_KTHREAD and PF_IO_WORKER with a NULL pt_regs, which
>> from my (arguably very short) checking is not commonly done for other
>> archs. This is fine, except when PF_IO_WORKER's have been created and
>> the task does something that causes a coredump to be generated. Then we
>> get this crash:
>
> Hey Jens,
>
> Thanks for the testing and the patch.
>
> I think your patch would work, but I'd be inclined to give the IO worker
> a pt_regs so it looks more like other archs and a regular user thread.
Yep I think that'd be a better idea. No better way to get a good patch
than to send out a bad one :-)
> Your IO worker bug reminded me to resurrect some copy_thread patches I
> had and I think they should do that
>
> https://lists.ozlabs.org/pipermail/linuxppc-dev/2023-March/256271.html
>
> I wouldn't ask you to test it until I've at least tried, do you have a
> test case that triggers this?
I can test them pretty easily. I did write a test case that is 100%
reliable for me, attached. Just do:
$ gcc -Wall -o ppc-crash ppc-crash.c -luring
$ ulimit -c10000000
$ ./ppc-crash
and it'll bomb while trying to write that coredump.
--
Jens Axboe
[-- Attachment #2: ppc-crash.c --]
[-- Type: text/x-csrc, Size: 709 bytes --]
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <liburing.h>
int main(int argc, char *argv[])
{
struct io_uring_sqe *sqe;
struct io_uring ring;
unsigned long *ptr = NULL;
char buf[16384];
char fname[32];
int fd[4];
int i;
for (i = 0; i < 4; i++) {
sprintf(fname, "/dev/shm/test.%d", i);
fd[i] = open(fname, O_RDWR | O_CREAT, 0644);
if (fd[i] < 0) {
perror("open");
return 1;
}
}
io_uring_queue_init(32, &ring, 0);
for (i = 0; i < 32; i++) {
unsigned long off = 16384 * (i / 4);
int index = i & 3;
sqe = io_uring_get_sqe(&ring);
io_uring_prep_write(sqe, fd[index], buf, sizeof(buf), off);
}
io_uring_submit(&ring);
usleep(1000);
*ptr = 0x1234;
}
next prev parent reply other threads:[~2023-03-27 12:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-26 22:15 [PATCH] powerpc: don't try to copy ppc for task with NULL pt_regs Jens Axboe
2023-03-27 6:36 ` Nicholas Piggin
2023-03-27 10:26 ` Christophe Leroy
2023-03-28 6:16 ` Nicholas Piggin
2023-03-28 11:47 ` Michael Ellerman
2023-03-30 8:44 ` Christophe Leroy
2023-03-27 12:42 ` Jens Axboe [this message]
2023-03-27 13:54 ` Michael Ellerman
2023-03-27 16:10 ` Jens Axboe
2023-03-28 11:32 ` Michael Ellerman
2023-03-28 12:39 ` Jens Axboe
2023-04-06 0:26 ` Michael Ellerman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1052468e-6b4e-16f2-a87e-fb403f0725f6@kernel.dk \
--to=axboe@kernel.dk \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=npiggin@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.