Re: [PATCH -mm] Taskstats fix the structure members alignment issue

[Balbir Singh <balbir@linux.vnet.ibm.com>]

Andrew Morton wrote:
> On Fri, 20 Apr 2007 22:13:41 +0530
> Balbir Singh <balbir@in.ibm.com> wrote:
>
> > We broke the the alignment of members of taskstats to the 8 byte boundary
> > with the CSA patches. In the current kernel, the taskstats structure is
> > not suitable for use by 32 bit applications in a 64 bit kernel.
>
> ugh, that was bad of us.

Yes :-)

> > ...
> > The patch adds an __attribute__((aligned(8))) to the
> > taskstats structure members so that 32 bit applications using taskstats
> > can work with a 64 bit kernel.
>
> But there might be 32-bit applications out there which are using the
> present wrong structure?
>
> otoh, I assume that those applications would be using taskstats.h and would
> hence encounter this bug and we would have heard about it, is that correct?

Yes, correct.

> otoh^2, 32-bit applications running under 32-bit kernels will presently be
> functioning correctly, and your change will require that those applications
> be recompiled, I think?

Yes, correct. They would be broken with this fix. We could  bump up the
version TASKSTATS_VERSION to 4. Would you like a new patch the version
bumped up?

> This patch looks like 2.6.20 and 2.6.21 material, but very carefully...

Yes, 2.6.20 and 2.6.21 sound correct.

--
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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