Re: [PATCH v3 00/16] Avoid MAP_FIXED gap exposure

[Bert Karwatzki <spasswolf@web.de>]

Am Freitag, dem 05.07.2024 um 11:06 -0400 schrieb Liam R. Howlett:
> * Bert Karwatzki <spasswolf@web.de> [240704 17:53]:
> > I just did test the v3 patchset on top of linux-next-20240703 with
> > `stress-ng --vm-segv 16`. In about 5 minutes of testing no errors occured.
> > This seems to be a good sign especially since testing the v2 patchset yielded
> > more than a million errors in 30 seconds.
> >
>
> Thanks.  I am still concerned about the group task exit issue you saw in
> v2 and how count could be out of sync with the mm struct map count.  I
> wonder if it was this set or something else that was in linux-next at
> the time of your testing.
>
> Were you closing a window in firefox when that happened?  Maybe I can
> attempt to recreate the issue again.
>
> Regards,
> Liam

I don't think I was closing a window when the issue happened, but right before
the freeze happened there was a segfault in a firefox process:

[ T8516] show_signal_msg: 16 callbacks suppressed
[ T8516] Isolated Web Co[8516]: segfault at 0 ip 00007f8c1f55fbe5 sp
00007ffcc2b97660 error 6 in libxul.so[4f98be5,7f8c1a686000+5f96000] likely on
CPU 14 (core 7, socket 0)
[ T8516] Code: 48 8d 0d 63 a3 3c 01 48 89 08 c7 04 25 00 00 00 00 00 00 00 00 0f
0b 48 8b 05 47 1a e2 03 48 8d 0d 38 99 30 01 48 89 08 31 c0 <89> 04 25 00 00 00
00 0f 0b e8 7d 7a 12 fb 66 2e 0f 1f 84 00 00 00
[ T8521] ------------[ cut here ]------------
[ T8521] kernel BUG at mm/mmap.c:3521!

so perhaps exit_group was called by a signal handler

Bert Karwatzki