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SubjectRe: [PATCH] sched: fair-group: fix a Div0 error of the fair group scheduler

* Miao Xie <miaox@cn.fujitsu.com> wrote:

> When I echoed 0 into the "cpu.shares" file, a Div0 error occured.
>
> We found it is caused by the following calling.
>
> sched_group_set_shares(tg, shares)
> set_se_shares(tg->se[i], shares/nr_cpu_ids)
> __set_se_shares(se, shares)
> div64_64((1ULL<<32), shares)
>
> When the echoed value was less than the number of processores, the
> result of the sentence "shares/nr_cpu_ids" was 0, and then the system
> called div64() to divide the result, the Div0 error occured.
>
> It is unnecessary that the shares value is divided by nr_cpu_ids, I
> think. Because in the function __update_group_shares_cpu() and
> init_tg_cfs_entry(), the shares value isn't divided by nr_cpu_ids when
> setting shares of the sched entity.
>
> This patch fixes this bug. And echoing ULONG_MAX value into cpu.shares
> also causes Div0 error, so we set a macro MAX_SHARES to limit the max
> value of shares.

thanks, applied.

Ingo


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