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Date: Fri, 26 Jul 2013 14:36:08 +0200 From: "Rafael J. Wysocki" <rjw@...k.pl> To: Lukasz Majewski <l.majewski@...sung.com> Cc: Viresh Kumar <viresh.kumar@...aro.org>, Zhang Rui <rui.zhang@...el.com>, Eduardo Valentin <eduardo.valentin@...com>, "cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>, Linux PM list <linux-pm@...r.kernel.org>, Jonghwa Lee <jonghwa3.lee@...sung.com>, Lukasz Majewski <l.majewski@...ess.pl>, linux-kernel <linux-kernel@...r.kernel.org>, Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>, Daniel Lezcano <daniel.lezcano@...aro.org>, Kukjin Kim <kgene.kim@...sung.com>, Myungjoo Ham <myungjoo.ham@...sung.com>, durgadoss.r@...el.com, Lists linaro-kernel <linaro-kernel@...ts.linaro.org> Subject: Re: [PATCH v6 2/8] cpufreq: Add boost frequency support in core On Friday, July 26, 2013 10:33:21 AM Lukasz Majewski wrote: > On Fri, 26 Jul 2013 12:47:15 +0530 Viresh Kumar wrote, > > On 25 July 2013 22:03, Lukasz Majewski <l.majewski@...sung.com> wrote: > > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > > > > > /********************************************************************* > > > + * > > > BOOST * > > > + > > > *********************************************************************/ > > > +static int cpufreq_boost_set_sw(int state) +{ > > > + struct cpufreq_frequency_table *freq_table; > > > + struct cpufreq_policy *policy; > > > + int ret = -EINVAL; > > > + > > > + list_for_each_entry(policy, &cpufreq_policy_list, > > > policy_list) { > > > + freq_table = > > > cpufreq_frequency_get_table(policy->cpu); > > > + if (freq_table) { > > > + ret = > > > cpufreq_frequency_table_cpuinfo(policy, > > > + freq_table); > > > + if (!ret) { > > > + policy->user_policy.max = > > > policy->max; > > > + __cpufreq_governor(policy, > > > CPUFREQ_GOV_LIMITS); > > > + } > > > + } > > > + } > > > + > > > + return ret; > > > +} > > > + > > > +int cpufreq_boost_trigger_state(int state) > > > +{ > > > + unsigned long flags; > > > + int ret = 0; > > > + > > > + if (cpufreq_driver->boost_enabled == state) > > > + return 0; > > > + > > > + write_lock_irqsave(&cpufreq_driver_lock, flags); > > > + cpufreq_driver->boost_enabled = state; > > > + write_unlock_irqrestore(&cpufreq_driver_lock, flags); > ^^^^^^^^^^^^^^^^^^^^ [*] > > > > Not sure if we should leave the lock at this point of time, as we > > haven't enabled boost until now. > > The problem here is with the cpufreq_driver->set_boost() call. > > I tried to avoid acquiring lock at one function and release it at > another (in this case cpufreq_boost_set_sw), especially since the > __cpufreq_governor() acquires its own lock - good place for deadlock. > > Is it OK for you to grab lock at one function > (cpufreq_boost_trigger_state()) and then at other function > (cpufreq_boost_set_sw) release it before calling __cpufreq_governor() > and grab it again after its completion? It generally is better to avoid doing that, although it is not unheard of. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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