arm: Convert VFP hotplug notifiers to state machine

Straight forward conversion plus commentary why code which is executed
in hotplug callbacks needs to be invoked before installing them.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153335.713612993@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 18 insertions, 11 deletions

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 73085d3482ed..da0b33deba6d 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -643,19 +643,19 @@ int vfp_restore_user_hwstate(struct user_vfp __user *ufp,
  * hardware state at every thread switch.  We clear our held state when
  * a CPU has been killed, indicating that the VFP hardware doesn't contain
  * a threads VFP state.  When a CPU starts up, we re-enable access to the
- * VFP hardware.
- *
- * Both CPU_DYING and CPU_STARTING are called on the CPU which
+ * VFP hardware. The callbacks below are called on the CPU which
  * is being offlined/onlined.
  */
-static int vfp_hotplug(struct notifier_block *b, unsigned long action,
-        void *hcpu)
+static int vfp_dying_cpu(unsigned int cpu)
 {
-        if (action == CPU_DYING || action == CPU_DYING_FROZEN)
-                vfp_current_hw_state[(long)hcpu] = NULL;
-        else if (action == CPU_STARTING || action == CPU_STARTING_FROZEN)
-                vfp_enable(NULL);
-        return NOTIFY_OK;
+        vfp_force_reload(cpu, current_thread_info());
+        return 0;
+}
+
+static int vfp_starting_cpu(unsigned int unused)
+{
+        vfp_enable(NULL);
+        return 0;
 }
 
 void vfp_kmode_exception(void)
@@ -732,6 +732,10 @@ static int __init vfp_init(void)
         unsigned int vfpsid;
         unsigned int cpu_arch = cpu_architecture();
 
+        /*
+         * Enable the access to the VFP on all online CPUs so the
+         * following test on FPSID will succeed.
+         */
         if (cpu_arch >= CPU_ARCH_ARMv6)
                 on_each_cpu(vfp_enable, NULL, 1);
 
@@ -794,7 +798,9 @@ static int __init vfp_init(void)
                 VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT;
         }
 
-        hotcpu_notifier(vfp_hotplug, 0);
+        cpuhp_setup_state_nocalls(CPUHP_AP_ARM_VFP_STARTING,
+                                  "AP_ARM_VFP_STARTING", vfp_starting_cpu,
+                                  vfp_dying_cpu);
 
         vfp_vector = vfp_support_entry;
 
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 3e719ba44fbe..4c63cb30aee6 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -34,6 +34,7 @@ enum cpuhp_state {
         CPUHP_AP_PERF_X86_CQM_STARTING,
         CPUHP_AP_PERF_X86_CSTATE_STARTING,
         CPUHP_AP_PERF_XTENSA_STARTING,
+        CPUHP_AP_ARM_VFP_STARTING,
         CPUHP_AP_NOTIFY_STARTING,
         CPUHP_AP_ONLINE,
         CPUHP_TEARDOWN_CPU,