Commit 1a1030d1 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

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
929ebc93 ("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: 929ebc93 ("cpufreq: intel_pstate: Set asymmetric CPU capacity on hybrid systems")
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reported-by: default avatar"Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com>
Link: https://patch.msgid.link/12554508.O9o76ZdvQC@rjwysocki.net


[ rjw: Changelog update ]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 92447aa5

drivers/cpufreq/intel_pstate.c

+16 −19
Original line number Diff line number Diff line
@@ -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;

	}



	/*
@@ -1056,20 +1059,14 @@ 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);



		hybrid_refresh_cpu_capacity_scaling();

		/*

		 * Disabling ITMT causes sched domains to be rebuilt to disable asym

		 * packing and enable asym capacity.

		 */

	if (disable_itmt)

		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);

}