From: Frans Klaver <fransklaver@gmail.com>
To: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>,
hpa@zytor.com, Frederic Weisbecker <fweisbec@gmail.com>,
torvalds@linux-foundation.org,
Thomas Gleixner <tglx@linutronix.de>,
wanpeng.li@hotmail.com,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Gustavo A. R. Silva" <garsilva@embeddedor.com>,
sgruszka@redhat.com, Peter Zijlstra <peterz@infradead.org>,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:sched/core] sched/cputime: Refactor the cputime_adjust() code
Date: Fri, 30 Jun 2017 16:41:50 +0200 [thread overview]
Message-ID: <CAH6sp9PbPt72HskuV+bLBz_sE9MS6EiXb0_n7K-JvRVrTe4J0g@mail.gmail.com> (raw)
In-Reply-To: <1498831200.6130.13.camel@redhat.com>
On Fri, Jun 30, 2017 at 4:00 PM, Rik van Riel <riel@redhat.com> wrote:
> On Fri, 2017-06-30 at 06:10 -0700, tip-bot for Gustavo A. R. Silva
> wrote:
>
>> +++ b/kernel/sched/cputime.c
>> @@ -615,19 +615,13 @@ static void cputime_adjust(struct task_cputime
>> *curr,
>> * userspace. Once a task gets some ticks, the monotonicy
>> code at
>> * 'update' will ensure things converge to the observed
>> ratio.
>> */
>> - if (stime == 0) {
>> - utime = rtime;
>> - goto update;
>> + if (stime != 0) {
>> + if (utime == 0)
>> + stime = rtime;
>> + else
>> + stime = scale_stime(stime, rtime, stime +
>> utime);
>> }
>>
>> - if (utime == 0) {
>> - stime = rtime;
>> - goto update;
>> - }
>> -
>> - stime = scale_stime(stime, rtime, stime + utime);
>> -
>> -update:
>
> Wait, what?
>
> This get rid of the utime = rtime assignment, when
> stime == 0. That could be a correctness issue.
The first time utime is used after that assignment, it is overwritten
with rtime - stime. The utime = rtime assignment is then pointless.
next prev parent reply other threads:[~2017-06-30 14:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-27 23:03 [kernel-sched-cputime] question about probable bug in cputime_adjust() Gustavo A. R. Silva
2017-06-28 5:35 ` Frans Klaver
2017-06-28 6:03 ` Frans Klaver
2017-06-28 23:57 ` Gustavo A. R. Silva
2017-06-29 4:51 ` Frans Klaver
2017-06-29 17:58 ` Gustavo A. R. Silva
2017-06-29 18:41 ` [PATCH] sched/cputime: code refactoring " Gustavo A. R. Silva
2017-06-30 13:10 ` [tip:sched/core] sched/cputime: Refactor the cputime_adjust() code tip-bot for Gustavo A. R. Silva
2017-06-30 14:00 ` Rik van Riel
2017-06-30 14:41 ` Frans Klaver [this message]
2017-06-30 15:46 ` Frederic Weisbecker
2017-06-30 16:17 ` Stanislaw Gruszka
2017-07-04 9:17 ` Peter Zijlstra
2017-07-04 10:01 ` Ingo Molnar
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