lkml.org 
[lkml]   [2019]   [Aug]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch V2 20/38] posix-cpu-timers: Provide array based access to expiry cache
On Wed, Aug 21, 2019 at 09:09:07PM +0200, Thomas Gleixner wrote:
> Using struct task_cputime for the expiry cache is a pretty odd choice and
> comes with magic defines to rename the fields for usage in the expiry
> cache.
>
> struct task_cputime is basically a u64 array with 3 members, but it has
> distinct members.
>
> The expiry cache content is different than the content of task_cputime
> because
>
> expiry[PROF] = task_cputime.stime + task_cputime.utime
> expiry[VIRT] = task_cputime.utime
> expiry[SCHED] = task_cputime.sum_exec_runtime
>
> So there is no direct mapping between task_cputime and the expiry cache and
> the #define based remapping is just a horrible hack.
>
> Having the expiry cache array based allows further simplification of the
> expiry code.
>
> To avoid an all in one cleanup which is hard to review add a temporary
> anonymous union into struct task_cputime which allows array based access to
> it. That requires to reorder the members. Add a build time sanity check to
> validate that the members are at the same place.
>
> The union and the build time checks will be removed after conversion.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

\
 
 \ /
  Last update: 2019-08-23 19:35    [W:0.763 / U:30.272 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site