Messages in this thread | | | Subject | Re: [PATCH] thermal: cpufreq_cooling: freq_qos_update_request() returns < 0 on error | From | Lukasz Luba <> | Date | Wed, 17 Feb 2021 10:45:53 +0000 |
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On 2/17/21 10:39 AM, Viresh Kumar wrote: > On 17-02-21, 10:29, Lukasz Luba wrote: >> On 2/17/21 5:48 AM, Viresh Kumar wrote: >>> freq_qos_update_request() returns 1 if the effective constraint value >>> has changed, 0 if the effective constraint value has not changed, or a >>> negative error code on failures. >>> >>> The frequency constraints for CPUs can be set by different parts of the >>> kernel. If the maximum frequency constraint set by other parts of the >>> kernel are set at a lower value than the one corresponding to cooling >>> state 0, then we will never be able to cool down the system as >>> freq_qos_update_request() will keep on returning 0 and we will skip >>> updating cpufreq_state and thermal pressure. >> >> To be precised, thermal pressure signal is not so important in this >> mechanism and the 'cpufreq_state' has changed recently: > > Right, I wasn't concerned only about no thermal cooling, but both > thermal cooling and pressure. > >> 236761f19a4f373354 thermal/drivers/cpufreq_cooling: Update cpufreq_state >> only if state has changed > > This moved the assignment to a more logical place for me, i.e. not to > do that on errors, just that the block in which it landed may not get > called at all :( > >>> Fix that by doing the updates even in the case where >>> freq_qos_update_request() returns 0, as we have effectively set the >>> constraint to a new value even if the consolidated value of the >>> actual constraint is unchanged because of external factors. >>> >>> Cc: v5.7+ <stable@vger.kernel.org> # v5.7+ >>> Reported-by: Thara Gopinath <thara.gopinath@linaro.org> >>> Fixes: f12e4f66ab6a ("thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping") >> >> I'm not sure if that f12e4f is the root cause. > > Hmm, depends on how we define the problem :) > > If this was just about thermal-cooling not happening, then may be yes, > but to me it is rather about mishandled return value of > freq_qos_update_request() which has more than one side effects and so > I went for the main commit. > > This is also important as f12e4f66ab6a got merged in 5.7 and 236761f19 > merged in 5.11 and this patch needs to get applied in stable kernels > since 5.7 to fix it all. >
'to fix it all' - I agree
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