Messages in this thread | | | Date | Wed, 3 Feb 2016 12:03:42 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH 2/5] cpufreq: governor: Create separate sysfs-ops |
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On 02-02-16, 17:01, Juri Lelli wrote: > Hi Rafael, > > On 02/02/16 17:35, Rafael J. Wysocki wrote: > > On Tue, Feb 2, 2016 at 4:47 PM, Juri Lelli <juri.lelli@arm.com> wrote:
> > > This patch cleans things up a lot, that's good. > > > > > > One thing I'm still concerned about, though: don't we need some locking > > > in place for some of the store operations on governors attributes? Are > > > store_{ignore_nice_load, sampling_down_fact, etc} safe without locking? > > > > That would require some investigation I suppose.
Yeah, that protection is required. Sorry about that.
> > > It seems that we can call them from different cpus concurrently. > > > > Yes, we can. > > > > One quick-and-dirty way of dealing with that might be to introduce a > > "sysfs lock" into struct dbs_data and hold that around the invocation > > of gattr->store() in the sysfs_ops's ->store callback.
s/dirty/sane ? :)
> Can't we actually try to use the policy->rwsem (or one of the core > locks) + wait_for_completion approach as we do in cpufreq core?
policy->rwsem will defeat the purpose of this change as it will reintroduce the ABBA issue.
-- viresh
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