[PATCH] kernel/sched/cputime: Fix unused value in cputime_adjust()

[PATCH] kernel/sched/cputime: Fix unused value in cputime_adjust()

[zengjx95]

From: Zeng Jingxiang <linuszeng@tencent.com>

Coverity warns uf an unused value:

assigned_value: Assign the value of the variable rtime to utime here,
but that stored value is overwritten before it can be used.
568	if (stime == 0) {
569		utime = rtime;
570		goto update;
571	}

value_overwrite: Overwriting previous write to utime with
the value of expression rtime - stime.
592	utime = rtime - stime;

Signed-off-by: Zeng Jingxiang <linuszeng@tencent.com>
---
 kernel/sched/cputime.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 78a233d43757..531df8b29e6d 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -565,10 +565,8 @@ void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
 	 * Once a task gets some ticks, the monotonicity code at 'update:'
 	 * will ensure things converge to the observed ratio.
 	 */
-	if (stime == 0) {
-		utime = rtime;
+	if (stime == 0)
 		goto update;
-	}
 
 	if (utime == 0) {
 		stime = rtime;
-- 
2.27.0

Re: [PATCH] kernel/sched/cputime: Fix unused value in cputime_adjust()

[Peter Zijlstra]

On Wed, Jul 20, 2022 at 06:29:56PM +0800, zengjx95@gmail.com wrote:
> From: Zeng Jingxiang <linuszeng@tencent.com>
> 
> Coverity warns uf an unused value:
> 
> assigned_value: Assign the value of the variable rtime to utime here,
> but that stored value is overwritten before it can be used.
> 568	if (stime == 0) {
> 569		utime = rtime;
> 570		goto update;
> 571	}
> 
> value_overwrite: Overwriting previous write to utime with
> the value of expression rtime - stime.
> 592	utime = rtime - stime;

Coverity is being daft, the compiler has a dead-store-elimination pass.

This way the code is more consistent / easier to ready.

Re: [PATCH] kernel/sched/cputime: Fix unused value in cputime_adjust()

[jingxiang zeng]

Peter Zijlstra <peterz@infradead.org> 于2022年7月20日周三 19:33写道：
>
> On Wed, Jul 20, 2022 at 06:29:56PM +0800, zengjx95@gmail.com wrote:
> > From: Zeng Jingxiang <linuszeng@tencent.com>
> >
> > Coverity warns uf an unused value:
> >
> > assigned_value: Assign the value of the variable rtime to utime here,
> > but that stored value is overwritten before it can be used.
> > 568   if (stime == 0) {
> > 569           utime = rtime;
> > 570           goto update;
> > 571   }
> >
> > value_overwrite: Overwriting previous write to utime with
> > the value of expression rtime - stime.
> > 592   utime = rtime - stime;
>
> Coverity is being daft, the compiler has a dead-store-elimination pass.
>
> This way the code is more consistent / easier to ready.


Thank you for your suggestion, I will try it.