Messages in this thread | | | From | Zhang Qiao <> | Subject | Re: [PATCH -next] sched: Dec __cfs_bandwith_used in destroy_cfs_bandwidth() | Date | Wed, 14 Jul 2021 19:20:39 +0800 |
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> On Tue, Jul 06, 2021 at 04:38:20PM +0800, Zhang Qiao wrote: >> __cfs_bandwith_uesd is a static_key to control cfs bandwidth >> feature. When adding a cfs_bandwidth group, we need increase >> the key, and decrease it when removing. But currently when we >> remove a cfs_bandwidth group, we don't decrease the key and >> this switch will always be on even if there is no cfs bandwidth >> group in the system. > > Yep, that's broken. > >> Therefore, when removing a cfs bandwidth group, we decrease >> __cfs_bandwith_used by calling cfs_bandwidth_usage_dec(). >> >> Fixes: 56f570e512ee ("sched: use jump labels to reduce overhead when bandwidth control is inactive") >> Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com> >> --- >> kernel/sched/fair.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 103e31e53e2b..857e8908b7f7 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -5344,6 +5344,9 @@ static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) >> if (!cfs_b->throttled_cfs_rq.next) >> return; >> >> + if (cfs_b->quota != RUNTIME_INF) >> + cfs_bandwidth_usage_dec(); > > This calls static_key_slow_dec_cpuslocked, but destroy_cfs_bandwidth > isn't holding the hotplug lock. > > The other caller of cfs_bandwidth_usage_dec needs to hold it for another > reason, so what about having both cfs_bandwidth_usage_dec() and > cfs_bandwidth_usage_dec_cpuslocked()? In that case, the _inc one could > be renamed similarly so this isn't a stumbling block later on. Hi Jordan, thanks for your comments.It is valuable to me.
And i have another thought is that we can hold the hotplug lock before calling cfs_bandwidth_usage_dec(). This way, fewer modifications are involved. What do you think about it?
thanks. > >> + >> hrtimer_cancel(&cfs_b->period_timer); >> hrtimer_cancel(&cfs_b->slack_timer); >> } >> -- >> 2.18.0.huawei.25 >>
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