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
929ebc9 ("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: 929ebc9 ("cpufreq: intel_pstate: Set asymmetric CPU capacity on hybrid systems")
Signed-off-by: Rafael J. Wysocki <[email protected]>
Reported-by: "Borah, Chaitanya Kumar" <[email protected]>
Link: https://patch.msgid.link/[email protected]
[ rjw: Changelog update ]
Signed-off-by: Rafael J. Wysocki <[email protected]>

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);
 }