xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

posix-cpu-timers: Provide array based access to expiry cache

Browse Source 
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>
Link: https://lkml.kernel.org/r/20190821192921.105793824@linutronix.de
This commit is contained in:
Thomas Gleixner
2019-08-21 21:09:07 +02:00
parent 3a245c0f11
commit 11b8462f7e
3 changed files with 31 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/sched/types.h
View File

@@ -6,8 +6,8 @@
/**
* struct task_cputime - collected CPU time counts
* @utime: time spent in user mode, in nanoseconds
* @stime: time spent in kernel mode, in nanoseconds
* @utime: time spent in user mode, in nanoseconds
* @sum_exec_runtime: total time spent on the CPU, in nanoseconds
*
* This structure groups together three kinds of CPU time that are tracked for
@@ -15,8 +15,8 @@
* these counts together and treat all three of them in parallel.
*/
struct task_cputime {
u64 utime;
u64 stime;
u64 utime;
unsigned long long sum_exec_runtime;
};