cpufreq: intel_pstate: Rearrange locking in hybrid_init_cpu_capacity_scaling()

Notice that hybrid_init_cpu_capacity_scaling() only needs to hold
hybrid_capacity_lock around __hybrid_init_cpu_capacity_scaling()
calls, so introduce a "locked" wrapper around the latter and call
it from the former.  This allows to drop a local variable and a
label that are not needed any more.

Also, rename __hybrid_init_cpu_capacity_scaling() to
__hybrid_refresh_cpu_capacity_scaling() for consistency.

Interestingly enough, this fixes a locking issue introduced by commit
929ebc93ccaa ("cpufreq: intel_pstate: Set asymmetric CPU capacity on
hybrid systems") that put an arch_enable_hybrid_capacity_scale() call
under hybrid_capacity_lock, which was a mistake because the latter is
acquired in CPU hotplug paths and so it cannot be held around
cpus_read_lock() calls.

Link: https://lore.kernel.org/linux-pm/SJ1PR11MB6129EDBF22F8A90FC3A3EDC8B9582@SJ1PR11MB6129.namprd11.prod.outlook.com/
Fixes: 929ebc93ccaa ("cpufreq: intel_pstate: Set asymmetric CPU capacity on hybrid systems")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reported-by: "Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com>
Link: https://patch.msgid.link/12554508.O9o76ZdvQC@rjwysocki.net
[ rjw: Changelog update ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index cd2ac1ba53d2a33d8d4310e76a04b2dca77e8f95..400337f3b572daba4285e9befa66a6e192fc548c 100644 (file)
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1028,26 +1028,29 @@ static void hybrid_update_cpu_capacity_scaling(void)
        }
 }
 
-static void __hybrid_init_cpu_capacity_scaling(void)
+static void __hybrid_refresh_cpu_capacity_scaling(void)
 {
        hybrid_max_perf_cpu = NULL;
        hybrid_update_cpu_capacity_scaling();
 }
 
-static void hybrid_init_cpu_capacity_scaling(bool refresh)
+static void hybrid_refresh_cpu_capacity_scaling(void)
 {
-       bool disable_itmt = false;
+       guard(mutex)(&hybrid_capacity_lock);
 
-       mutex_lock(&hybrid_capacity_lock);
+       __hybrid_refresh_cpu_capacity_scaling();
+}
 
+static void hybrid_init_cpu_capacity_scaling(bool refresh)
+{
        /*
         * If hybrid_max_perf_cpu is set at this point, the hybrid CPU capacity
         * scaling has been enabled already and the driver is just changing the
         * operation mode.
         */
        if (refresh) {
-               __hybrid_init_cpu_capacity_scaling();
-               goto unlock;
+               hybrid_refresh_cpu_capacity_scaling();
+               return;
        }
 
        /*
@@ -1056,19 +1059,13 @@ static void hybrid_init_cpu_capacity_scaling(bool refresh)
         * do not do that when SMT is in use.
         */
        if (hwp_is_hybrid && !sched_smt_active() && arch_enable_hybrid_capacity_scale()) {
-               __hybrid_init_cpu_capacity_scaling();
-               disable_itmt = true;
-       }
-
-unlock:
-       mutex_unlock(&hybrid_capacity_lock);
-
-       /*
-        * Disabling ITMT causes sched domains to be rebuilt to disable asym
-        * packing and enable asym capacity.
-        */
-       if (disable_itmt)
+               hybrid_refresh_cpu_capacity_scaling();
+               /*
+                * Disabling ITMT causes sched domains to be rebuilt to disable asym
+                * packing and enable asym capacity.
+                */
                sched_clear_itmt_support();
+       }
 }
 
 static bool hybrid_clear_max_perf_cpu(void)
@@ -1404,7 +1401,7 @@ static void intel_pstate_update_limits_for_all(void)
        mutex_lock(&hybrid_capacity_lock);
 
        if (hybrid_max_perf_cpu)
-               __hybrid_init_cpu_capacity_scaling();
+               __hybrid_refresh_cpu_capacity_scaling();
 
        mutex_unlock(&hybrid_capacity_lock);
 }