cpufreq: intel_pstate: Always read hwp_cap_cached with READ_ONCE()

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>
Tested-by: Chen Yu <yu.c.chen@intel.com>

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index be05e03..74bf54e 100644 (file)
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -914,7 +914,7 @@ static void intel_pstate_hwp_offline(struct cpudata *cpu)
        }
 
        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 * NSEC_PER_MSEC;
 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_boost_up(struct cpudata *cpu)
                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;