[PATCH v1 1/3] cpufreq: intel_pstate: Always read hwp_cap_cached with READ_ONCE()

Rafael J. Wysocki
2021-01-07T18:45:35Z

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Because intel_pstate_get_hwp_max() which updates hwp_cap_cached
may run in parallel with the readers of it, annotate all of the
read accesses to it with READ_ONCE().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/cpufreq/intel_pstate.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -914,7 +914,7 @@ static void intel_pstate_hwp_offline(str
}

value &= ~GENMASK_ULL(31, 0);
- min_perf = HWP_LOWEST_PERF(cpu->hwp_cap_cached);
+ min_perf = HWP_LOWEST_PERF(READ_ONCE(cpu->hwp_cap_cached));

/* Set hwp_max = hwp_min */
value |= HWP_MAX_PERF(min_perf);
@@ -1750,6 +1750,7 @@ static int hwp_boost_hold_time_ns = 3 *
static inline void intel_pstate_hwp_boost_up(struct cpudata *cpu)
{
u64 hwp_req = READ_ONCE(cpu->hwp_req_cached);
+ u64 hwp_cap = READ_ONCE(cpu->hwp_cap_cached);
u32 max_limit = (hwp_req & 0xff00) >> 8;
u32 min_limit = (hwp_req & 0xff);
u32 boost_level1;
@@ -1776,14 +1777,14 @@ static inline void intel_pstate_hwp_boos
cpu->hwp_boost_min = min_limit;

/* level at half way mark between min and guranteed */
- boost_level1 = (HWP_GUARANTEED_PERF(cpu->hwp_cap_cached) + min_limit) >> 1;
+ boost_level1 = (HWP_GUARANTEED_PERF(hwp_cap) + min_limit) >> 1;

if (cpu->hwp_boost_min < boost_level1)
cpu->hwp_boost_min = boost_level1;
- else if (cpu->hwp_boost_min < HWP_GUARANTEED_PERF(cpu->hwp_cap_cached))
- cpu->hwp_boost_min = HWP_GUARANTEED_PERF(cpu->hwp_cap_cached);
- else if (cpu->hwp_boost_min == HWP_GUARANTEED_PERF(cpu->hwp_cap_cached) &&
- max_limit != HWP_GUARANTEED_PERF(cpu->hwp_cap_cached))
+ else if (cpu->hwp_boost_min < HWP_GUARANTEED_PERF(hwp_cap))
+ cpu->hwp_boost_min = HWP_GUARANTEED_PERF(hwp_cap);
+ else if (cpu->hwp_boost_min == HWP_GUARANTEED_PERF(hwp_cap) &&
+ max_limit != HWP_GUARANTEED_PERF(hwp_cap))
cpu->hwp_boost_min = max_limit;
else
return;