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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-05-04 15:01:10 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-05-04 15:09:16 +0300
commit6d45b719cbd51f014bb1b5dd8ed99068d78d36af (patch)
treec49822a308038696cbea7e1ea466a6b3248b1efd /drivers/cpufreq
parentba41e1bc28bd862089b0fc00e8136aa258a62b21 (diff)
downloadlinux-6d45b719cbd51f014bb1b5dd8ed99068d78d36af.tar.xz
intel_pstate: Fix intel_pstate_get()
After commit 8fa520af5081 "intel_pstate: Remove freq calculation from intel_pstate_calc_busy()" intel_pstate_get() calls get_avg_frequency() to compute the average frequency, which is problematic for two reasons. First, intel_pstate_get() may be invoked before the driver reads the CPU feedback registers for the first time and if that happens, get_avg_frequency() will attempt to divide by zero. Second, the get_avg_frequency() call in intel_pstate_get() is racy with respect to intel_pstate_sample() and it may end up returning completely meaningless values for this reason. Moreover, after commit 7349ec0470b6 "intel_pstate: Move intel_pstate_calc_busy() into get_target_pstate_use_performance()" sample.core_pct_busy is never computed on Atom, but it is used in intel_pstate_adjust_busy_pstate() in that case too. To address those problems notice that if sample.core_pct_busy was used in the average frequency computation carried out by get_avg_frequency(), both the divide by zero problem and the race with respect to intel_pstate_sample() would be avoided. Accordingly, move the invocation of intel_pstate_calc_busy() from get_target_pstate_use_performance() to intel_pstate_update_util(), which also will take care of the uninitialized sample.core_pct_busy on Atom, and modify get_avg_frequency() to use sample.core_pct_busy as per the above. Reported-by: kernel test robot <ying.huang@linux.intel.com> Link: http://marc.info/?l=linux-kernel&m=146226437623173&w=4 Fixes: 8fa520af5081 "intel_pstate: Remove freq calculation from intel_pstate_calc_busy()" Fixes: 7349ec0470b6 "intel_pstate: Move intel_pstate_calc_busy() into get_target_pstate_use_performance()" Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r--drivers/cpufreq/intel_pstate.c14
1 files changed, 8 insertions, 6 deletions
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 66f7f0071cab..b230ebaae66c 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1070,8 +1070,9 @@ static inline bool intel_pstate_sample(struct cpudata *cpu, u64 time)
static inline int32_t get_avg_frequency(struct cpudata *cpu)
{
- return div64_u64(cpu->pstate.max_pstate_physical * cpu->sample.aperf *
- cpu->pstate.scaling, cpu->sample.mperf);
+ return fp_toint(mul_fp(cpu->sample.core_pct_busy,
+ int_tofp(cpu->pstate.max_pstate_physical *
+ cpu->pstate.scaling / 100)));
}
static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu)
@@ -1114,8 +1115,6 @@ static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu)
int32_t core_busy, max_pstate, current_pstate, sample_ratio;
u64 duration_ns;
- intel_pstate_calc_busy(cpu);
-
/*
* core_busy is the ratio of actual performance to max
* max_pstate is the max non turbo pstate available
@@ -1199,8 +1198,11 @@ static void intel_pstate_update_util(struct update_util_data *data, u64 time,
if ((s64)delta_ns >= pid_params.sample_rate_ns) {
bool sample_taken = intel_pstate_sample(cpu, time);
- if (sample_taken && !hwp_active)
- intel_pstate_adjust_busy_pstate(cpu);
+ if (sample_taken) {
+ intel_pstate_calc_busy(cpu);
+ if (!hwp_active)
+ intel_pstate_adjust_busy_pstate(cpu);
+ }
}
}