Messages in this thread | | | Date | Thu, 24 Sep 2020 10:27:51 -0400 | From | Tejun Heo <> | Subject | Re: sched: rq->nr_iowait transiently going negative after the recent p->on_cpu optimization |
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Hello,
On Thu, Sep 24, 2020 at 01:50:42PM +0200, Peter Zijlstra wrote: > Hurmph.. I suppose you're right :/ And this is an actual problem?
Yeah, this got exposed to userspace as a full 64bit number which overflowed u32 conversion in the rust procfs library which aborted a program I was working on multiple times over several months.
On a more theoretical side, it might also surprise nr_iowait_cpu() users. However, a real problem that may be.
> I think the below should cure that, but blergh, not nice. If you could > confirm, I'll try and think of something nicer.
Rik suggested that it'd be sufficient to return 0 on underflow especially given that 0 is actually the right number to describe the state. So, maybe that can be a nicer code-wise?
Thanks.
-- tejun
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