Messages in this thread Patch in this message | | | Date | Tue, 16 Jun 2020 10:48:02 +0100 | From | Quentin Perret <> | Subject | Re: [PATCH 2/2] cpufreq: Specify default governor on command line |
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On Tuesday 16 Jun 2020 at 14:57:59 (+0530), Viresh Kumar wrote: > There is another problem here which we need to look at. Any governor > which is built as a module and isn't currently used, should be allowed > to unload. And this needs to be tested by you as well, should be easy > enough. > > With the current implementation, you take a reference to the default > governor when the driver is registered and drop it only when the > driver goes away. Which means we won't be able to unload the module of > the governor even if it isn't used. Which is wrong. The solution I > proposed had the same issue as well. > > You need to figure out a way where we don't need to keep holding the > module hostage even when it isn't used. I see two ways at least for > the same: > > - Do that from the existing place: cpufreq_init_policy(). > > - And I think this can be done from governor-register/unregister as > well. > > Second one sounds good, if it is feasible to do that.
Good point.
I'm thinking something along the lines of:
---8<--- diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 0f05caedc320..a9219404e07f 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -2340,6 +2340,11 @@ int cpufreq_register_governor(struct cpufreq_governor *governor) list_add(&governor->governor_list, &cpufreq_governor_list); } + if (!strncasecmp(cpufreq_param_governor, governor->name, CPUFREQ_NAME_LEN)) + default_governor = governor; + else if (!default_governor && cpufreq_default_governor() == governor) + default_governor = cpufreq_default_governor(); + mutex_unlock(&cpufreq_governor_mutex); return err; } @@ -2368,6 +2373,8 @@ void cpufreq_unregister_governor(struct cpufreq_governor *governor) mutex_lock(&cpufreq_governor_mutex); list_del(&governor->governor_list); + if (governor == default_governor) + default_governor = cpufreq_default_governor(); mutex_unlock(&cpufreq_governor_mutex); } EXPORT_SYMBOL_GPL(cpufreq_unregister_governor); --->8--- should do the trick. That removes the unnecessary reference count, and feels like a good place to hook things -- that is how cpuidle does it too IIRC.
I'll double check the locking/synchronization, but that shouldn't be too bad (famous last words).
Cheers, Quentin
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