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Message-ID: <3a70280b-8cc4-9f22-92b7-088fa9cb45df@linaro.org> Date: Mon, 23 Oct 2023 20:23:49 +0200 From: Daniel Lezcano <daniel.lezcano@...aro.org> To: Lukasz Luba <lukasz.luba@....com>, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, rafael@...nel.org Cc: dietmar.eggemann@....com, rui.zhang@...el.com, amit.kucheria@...durent.com, amit.kachhap@...il.com, viresh.kumar@...aro.org, len.brown@...el.com, pavel@....cz, mhiramat@...nel.org, qyousef@...alina.io, wvw@...gle.com Subject: Re: [PATCH v4 06/18] PM: EM: Check if the get_cost() callback is present in em_compute_costs() On 25/09/2023 10:11, Lukasz Luba wrote: > The em_compute_cost() is going to be re-used in runtime modified EM > code path. Thus, make sure that this common code is safe and won't > try to use the NULL pointer. The former em_compute_cost() didn't have to > care about runtime modification code path. The upcoming changes introduce > such option, but with different callback. Those two paths which use > get_cost() (during first EM registration) or update_power() (during > runtime modification) need to be safely handled in em_compute_costs(). > > Signed-off-by: Lukasz Luba <lukasz.luba@....com> > --- > kernel/power/energy_model.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c > index 7ea882401833..35e07933b34a 100644 > --- a/kernel/power/energy_model.c > +++ b/kernel/power/energy_model.c > @@ -116,7 +116,7 @@ static int em_compute_costs(struct device *dev, struct em_perf_state *table, > for (i = nr_states - 1; i >= 0; i--) { > unsigned long power_res, cost; > > - if (flags & EM_PERF_DOMAIN_ARTIFICIAL) { > + if (flags & EM_PERF_DOMAIN_ARTIFICIAL && cb->get_cost) { > ret = cb->get_cost(dev, table[i].frequency, &cost); > if (ret || !cost || cost > EM_MAX_POWER) { > dev_err(dev, "EM: invalid cost %lu %d\n", I do believe & operator has lower precedence than && operator, thus the test is actually: (flags & (EM_PERF_DOMAIN_ARTIFICIAL && cb->get_cost)) but it should be ((flags & EM_PERF_DOMAIN_ARTIFICIAL) && cb->get_cost) Right ? -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
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