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cpufreq: governor: Ensure sufficiently large sampling intervals
commit56026645e2
upstream. After commitaa7519af45
(cpufreq: Use transition_delay_us for legacy governors as well) the sampling_rate field of struct dbs_data may be less than the tick period which causes dbs_update() to produce incorrect results, so make the code ensure that the value of that field will always be sufficiently large. Fixes:aa7519af45
(cpufreq: Use transition_delay_us for legacy governors as well) Reported-by: Andy Tang <andy.tang@nxp.com> Reported-by: Doug Smythies <dsmythies@telus.net> Tested-by: Andy Tang <andy.tang@nxp.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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c43db1a3c7
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c83189edf4
1 changed files with 16 additions and 3 deletions
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@ -22,6 +22,8 @@
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#include "cpufreq_governor.h"
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#define CPUFREQ_DBS_MIN_SAMPLING_INTERVAL (2 * TICK_NSEC / NSEC_PER_USEC)
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static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs);
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static DEFINE_MUTEX(gov_dbs_data_mutex);
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@ -47,11 +49,15 @@ ssize_t store_sampling_rate(struct gov_attr_set *attr_set, const char *buf,
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{
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struct dbs_data *dbs_data = to_dbs_data(attr_set);
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struct policy_dbs_info *policy_dbs;
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unsigned int sampling_interval;
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int ret;
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ret = sscanf(buf, "%u", &dbs_data->sampling_rate);
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if (ret != 1)
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ret = sscanf(buf, "%u", &sampling_interval);
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if (ret != 1 || sampling_interval < CPUFREQ_DBS_MIN_SAMPLING_INTERVAL)
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return -EINVAL;
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dbs_data->sampling_rate = sampling_interval;
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/*
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* We are operating under dbs_data->mutex and so the list and its
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* entries can't be freed concurrently.
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@ -430,7 +436,14 @@ int cpufreq_dbs_governor_init(struct cpufreq_policy *policy)
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if (ret)
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goto free_policy_dbs_info;
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dbs_data->sampling_rate = cpufreq_policy_transition_delay_us(policy);
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/*
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* The sampling interval should not be less than the transition latency
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* of the CPU and it also cannot be too small for dbs_update() to work
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* correctly.
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*/
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dbs_data->sampling_rate = max_t(unsigned int,
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CPUFREQ_DBS_MIN_SAMPLING_INTERVAL,
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cpufreq_policy_transition_delay_us(policy));
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if (!have_governor_per_policy())
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gov->gdbs_data = dbs_data;
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