ARM/hw_breakpoint: Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

smp_call_function_single() has been removed because the function is already
invoked on the target CPU.

[ tglx: Added protection agaist hotplug back according to discussion with Will ]

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: rt@linuxtronix.de
Cc: Will Deacon <will.deacon@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/20161117183541.8588-16-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index b8df45883cf78e36aab24522d0da348335801695..188180b5523de09f55647d2d31547684c450a8c7 100644 (file)
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -925,9 +925,9 @@ static bool core_has_os_save_restore(void)
        }
 }
 
-static void reset_ctrl_regs(void *unused)
+static void reset_ctrl_regs(unsigned int cpu)
 {
-       int i, raw_num_brps, err = 0, cpu = smp_processor_id();
+       int i, raw_num_brps, err = 0;
        u32 val;
 
        /*
@@ -1020,25 +1020,20 @@ out_mdbgen:
                cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
 }
 
-static int dbg_reset_notify(struct notifier_block *self,
-                                     unsigned long action, void *cpu)
+static int dbg_reset_online(unsigned int cpu)
 {
-       if ((action & ~CPU_TASKS_FROZEN) == CPU_ONLINE)
-               smp_call_function_single((int)cpu, reset_ctrl_regs, NULL, 1);
-
-       return NOTIFY_OK;
+       local_irq_disable();
+       reset_ctrl_regs(cpu);
+       local_irq_enable();
+       return 0;
 }
 
-static struct notifier_block dbg_reset_nb = {
-       .notifier_call = dbg_reset_notify,
-};
-
 #ifdef CONFIG_CPU_PM
 static int dbg_cpu_pm_notify(struct notifier_block *self, unsigned long action,
                             void *v)
 {
        if (action == CPU_PM_EXIT)
-               reset_ctrl_regs(NULL);
+               reset_ctrl_regs(smp_processor_id());
 
        return NOTIFY_OK;
 }
@@ -1059,6 +1054,8 @@ static inline void pm_init(void)
 
 static int __init arch_hw_breakpoint_init(void)
 {
+       int ret;
+
        debug_arch = get_debug_arch();
 
        if (!debug_arch_supported()) {
@@ -1072,25 +1069,28 @@ static int __init arch_hw_breakpoint_init(void)
        core_num_brps = get_num_brps();
        core_num_wrps = get_num_wrps();
 
-       cpu_notifier_register_begin();
-
        /*
         * We need to tread carefully here because DBGSWENABLE may be
         * driven low on this core and there isn't an architected way to
         * determine that.
         */
+       get_online_cpus();
        register_undef_hook(&debug_reg_hook);
 
        /*
-        * Reset the breakpoint resources. We assume that a halting
-        * debugger will leave the world in a nice state for us.
+        * Register CPU notifier which resets the breakpoint resources. We
+        * assume that a halting debugger will leave the world in a nice state
+        * for us.
         */
-       on_each_cpu(reset_ctrl_regs, NULL, 1);
+       ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "arm/hw_breakpoint:online",
+                               dbg_reset_online, NULL);
        unregister_undef_hook(&debug_reg_hook);
-       if (!cpumask_empty(&debug_err_mask)) {
+       if (WARN_ON(ret < 0) || !cpumask_empty(&debug_err_mask)) {
                core_num_brps = 0;
                core_num_wrps = 0;
-               cpu_notifier_register_done();
+               if (ret > 0)
+                       cpuhp_remove_state_nocalls(ret);
+               put_online_cpus();
                return 0;
        }
 
@@ -1108,12 +1108,9 @@ static int __init arch_hw_breakpoint_init(void)
                        TRAP_HWBKPT, "watchpoint debug exception");
        hook_ifault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
                        TRAP_HWBKPT, "breakpoint debug exception");
+       put_online_cpus();
 
-       /* Register hotplug and PM notifiers. */
-       __register_cpu_notifier(&dbg_reset_nb);
-
-       cpu_notifier_register_done();
-
+       /* Register PM notifiers. */
        pm_init();
        return 0;
 }