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| author | Miao Xie <miaox@cn.fujitsu.com> | 2008-04-28 12:54:56 +0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-05-05 23:56:18 +0200 |
| commit | cb4ad1ffc7c0d8ea7dc8cd8ba303d83551716d46 (patch) | |
| tree | 79f6b1fe971a270e5e009d695d2bf998936197c8 /kernel/sched.c | |
| parent | 712555ee4f873515612f89554ad1a3fda5fa887e (diff) | |
| download | lwn-cb4ad1ffc7c0d8ea7dc8cd8ba303d83551716d46.tar.gz lwn-cb4ad1ffc7c0d8ea7dc8cd8ba303d83551716d46.zip | |
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>
Diffstat (limited to 'kernel/sched.c')
| -rw-r--r-- | kernel/sched.c | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 561b3b39bdb8..f98f75f3c708 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -321,7 +321,13 @@ static DEFINE_SPINLOCK(task_group_lock); # define INIT_TASK_GROUP_LOAD NICE_0_LOAD #endif +/* + * A weight of 0, 1 or ULONG_MAX can cause arithmetics problems. + * (The default weight is 1024 - so there's no practical + * limitation from this.) + */ #define MIN_SHARES 2 +#define MAX_SHARES (ULONG_MAX - 1) static int init_task_group_load = INIT_TASK_GROUP_LOAD; #endif @@ -1804,6 +1810,8 @@ __update_group_shares_cpu(struct task_group *tg, struct sched_domain *sd, if (shares < MIN_SHARES) shares = MIN_SHARES; + else if (shares > MAX_SHARES) + shares = MAX_SHARES; __set_se_shares(tg->se[tcpu], shares); } @@ -8785,13 +8793,10 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares) if (!tg->se[0]) return -EINVAL; - /* - * A weight of 0 or 1 can cause arithmetics problems. - * (The default weight is 1024 - so there's no practical - * limitation from this.) - */ if (shares < MIN_SHARES) shares = MIN_SHARES; + else if (shares > MAX_SHARES) + shares = MAX_SHARES; mutex_lock(&shares_mutex); if (tg->shares == shares) @@ -8816,7 +8821,7 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares) * force a rebalance */ cfs_rq_set_shares(tg->cfs_rq[i], 0); - set_se_shares(tg->se[i], shares/nr_cpu_ids); + set_se_shares(tg->se[i], shares); } /* |