From cd59b4bed9d11a2aefc4bb44eed9de0e6c1eea06 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Wed, 1 Mar 2017 00:07:36 +0100 Subject: [PATCH] cpufreq: intel_pstate: Fix global settings in active mode Commit 111b8b3fe4fa (cpufreq: intel_pstate: Always keep all limits settings in sync) changed intel_pstate to invoke cpufreq_update_policy() for every registered CPU on global sysfs attributes updates, but that led to undesirable effects in the active mode if the "performance" P-state selection algorithm is configufred for one CPU and the "powersave" one is chosen for all of the other CPUs. Namely, in that case, the following is possible: # cd /sys/devices/system/cpu/ # cat intel_pstate/max_perf_pct 100 # cat intel_pstate/min_perf_pct 26 # echo performance > cpufreq/policy0/scaling_governor # cat intel_pstate/max_perf_pct 100 # cat intel_pstate/min_perf_pct 100 # echo 94 > intel_pstate/min_perf_pct # cat intel_pstate/min_perf_pct 26 The reason why this happens is because intel_pstate attempts to maintain two sets of global limits in the active mode, one for the "performance" P-state selection algorithm and one for the "powersave" P-state selection algorithm, but the P-state selection algorithms are set per policy, so the global limits cannot reflect all of them at the same time if they are different for different policies. In the particular situation above, the attempt to change min_perf_pct to 94 caused cpufreq_update_policy() to be run for a CPU with the "powersave" P-state selection algorithm and intel_pstate_set_policy() called by it silently switched the global limits to the "powersave" set which finally was reflected by the sysfs interface. To prevent that from happening, modify intel_pstate_update_policies() to always switch back to the set of limits that was used right before it has been invoked. Fixes: 111b8b3fe4fa (cpufreq: intel_pstate: Always keep all limits settings in sync) Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/intel_pstate.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 5e066b3..436a4c5 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -973,11 +973,20 @@ static int intel_pstate_resume(struct cpufreq_policy *policy) } static void intel_pstate_update_policies(void) + __releases(&intel_pstate_limits_lock) + __acquires(&intel_pstate_limits_lock) { + struct perf_limits *saved_limits = limits; int cpu; + mutex_unlock(&intel_pstate_limits_lock); + for_each_possible_cpu(cpu) cpufreq_update_policy(cpu); + + mutex_lock(&intel_pstate_limits_lock); + + limits = saved_limits; } /************************** debugfs begin ************************/ @@ -1185,10 +1194,10 @@ static ssize_t store_no_turbo(struct kobject *a, struct attribute *b, limits->no_turbo = clamp_t(int, input, 0, 1); - mutex_unlock(&intel_pstate_limits_lock); - intel_pstate_update_policies(); + mutex_unlock(&intel_pstate_limits_lock); + mutex_unlock(&intel_pstate_driver_lock); return count; @@ -1222,10 +1231,10 @@ static ssize_t store_max_perf_pct(struct kobject *a, struct attribute *b, limits->max_perf_pct); limits->max_perf = div_ext_fp(limits->max_perf_pct, 100); - mutex_unlock(&intel_pstate_limits_lock); - intel_pstate_update_policies(); + mutex_unlock(&intel_pstate_limits_lock); + mutex_unlock(&intel_pstate_driver_lock); return count; @@ -1259,10 +1268,10 @@ static ssize_t store_min_perf_pct(struct kobject *a, struct attribute *b, limits->min_perf_pct); limits->min_perf = div_ext_fp(limits->min_perf_pct, 100); - mutex_unlock(&intel_pstate_limits_lock); - intel_pstate_update_policies(); + mutex_unlock(&intel_pstate_limits_lock); + mutex_unlock(&intel_pstate_driver_lock); return count; -- 2.7.4