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

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wyso...@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.wyso...@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;