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Subject[tip:smp/hotplug] ARM/hw_breakpoint: Convert to hotplug state machine
Commit-ID:  3b341295030a327d7c763630f865fbf20a1df1c8
Gitweb: http://git.kernel.org/tip/3b341295030a327d7c763630f865fbf20a1df1c8
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Thu, 17 Nov 2016 19:35:36 +0100
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 21 Nov 2016 16:37:08 +0100

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>

---
arch/arm/kernel/hw_breakpoint.c | 47 +++++++++++++++++++----------------------
1 file changed, 22 insertions(+), 25 deletions(-)

diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index b8df458..188180b 100644
--- 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;
}
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