container_of

[Simon Brand]

Am Sat, 17 Jan 2015 08:58:13 -0800
schrieb Manish Katiyar <mkatiyar at gmail.com>:

> Have you searched through archives. Exactly 7 years ago, I had the
> same question.
> 
> http://comments.gmane.org/gmane.linux.kernel.kernelnewbies/24141
> 

No, sorry, I missed that :-x
Thank you.

To get this straight: it is only to produce a warning at compile time,
when it is misused?


I compiled the kernel two times, one time with the original code and
one time with
#define container_of(ptr, type, member) ({			\
	(type *)( (char *)ptr - offsetof(type,member) );})


The secound kernel does not work proberly. 
First there is a kernel BUG at include/drm/drm_mm.h:145 at every boot:
http://sprunge.us/MdDa

Secound the kernel hangs on reboot and poweroff:
reboot:
http://picpaste.de/pics/8a041c11f3f5e24faebc1abb41b1db3f.1421523345.png
poweroff:
http://picpaste.de/pics/b1ab5225f37572a31b43e2fb8526e890.1421523472.png

Third for example startx only produces the output:
waiting for X server to begin accepting connections

There is no further output in dmesg.

The X server starts correctly with the first/original kernel.

I compiled both kernels with following config:
https://projects.archlinux.org/svntogit/packages.git/plain/trunk/config.x86_64?h=packages/linux
and following patches:
https://projects.archlinux.org/svntogit/packages.git/plain/trunk/0001-drm-i915-Disallow-pin-ioctl-completely-for-kms-drive.patch?h=packages/linux
https://projects.archlinux.org/svntogit/packages.git/plain/trunk/change-default-console-loglevel.patch?h=packages/linux


I compiled a little c code with both defines and gcc is producing
another binary, but both are working as they should.


Thank you for your reply.
Simon