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sched: fair-group: fix a Div0 error of the fair group scheduler
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. Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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1 changed files with 11 additions and 6 deletions
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@ -321,7 +321,13 @@ static DEFINE_SPINLOCK(task_group_lock);
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# define INIT_TASK_GROUP_LOAD NICE_0_LOAD
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#endif
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/*
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* A weight of 0, 1 or ULONG_MAX can cause arithmetics problems.
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* (The default weight is 1024 - so there's no practical
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* limitation from this.)
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*/
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#define MIN_SHARES 2
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#define MAX_SHARES (ULONG_MAX - 1)
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static int init_task_group_load = INIT_TASK_GROUP_LOAD;
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#endif
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@ -1804,6 +1810,8 @@ __update_group_shares_cpu(struct task_group *tg, struct sched_domain *sd,
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if (shares < MIN_SHARES)
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shares = MIN_SHARES;
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else if (shares > MAX_SHARES)
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shares = MAX_SHARES;
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__set_se_shares(tg->se[tcpu], shares);
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}
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@ -8785,13 +8793,10 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
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if (!tg->se[0])
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return -EINVAL;
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/*
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* A weight of 0 or 1 can cause arithmetics problems.
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* (The default weight is 1024 - so there's no practical
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* limitation from this.)
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*/
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if (shares < MIN_SHARES)
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shares = MIN_SHARES;
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else if (shares > MAX_SHARES)
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shares = MAX_SHARES;
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mutex_lock(&shares_mutex);
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if (tg->shares == shares)
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@ -8816,7 +8821,7 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
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* force a rebalance
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*/
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cfs_rq_set_shares(tg->cfs_rq[i], 0);
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set_se_shares(tg->se[i], shares/nr_cpu_ids);
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set_se_shares(tg->se[i], shares);
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}
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/*
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