Messages in this thread | | | Date | Thu, 1 Sep 2022 15:03:11 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH v2 5/5] sched/fair: cleanup for SIS_PROP |
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On Thu, Sep 01, 2022 at 09:11:07PM +0800, Abel Wu wrote: > The sched-domain of this cpu is only used when SIS_PROP is enabled, > and it should be irrelevant whether the local sd_llc is valid or > not, since all we care about is target sd_llc if !SIS_PROP. > > Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
This could conceivably result in an uninitialised memory access if SIS_PROP was enabled while select_idle_cpu is running. I'm not sure if it can happen when jump labels are in use but I think it could happen for !CONFIG_JUMP_LABEL updating the sysctl_sched_features bitmap updated via sysctl.
The patch is still a good idea because it moves an unlikely rcu_deference out of the default path for sched features but either this_sd needs to be initialised to NULL and checked or the this_sd lookup needs to happen twice at a slight additional cost to the default-disabled SIS_PROP path.
-- Mel Gorman SUSE Labs
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