ARM/hw_breakpoint: Use cpuhp_setup_state_cpuslocked()

arch_hw_breakpoint_init() holds get_online_cpus() while registerring the
hotplug callbacks.

cpuhp_setup_state() invokes get_online_cpus() as well. This is correct, but
prevents the conversion of the hotplug locking to a percpu rwsem.

Use cpuhp_setup_state_cpuslocked() to avoid the nested call. Convert
*_online_cpus() to the new interfaces while at it.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/20170524081548.170940729@linutronix.de

diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index be3b3fb..63cb4c7 100644 (file)
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -1090,7 +1090,7 @@ static int __init arch_hw_breakpoint_init(void)
         * driven low on this core and there isn't an architected way to
         * determine that.
         */
-       get_online_cpus();
+       cpus_read_lock();
        register_undef_hook(&debug_reg_hook);
 
        /*
@@ -1098,15 +1098,16 @@ static int __init arch_hw_breakpoint_init(void)
         * assume that a halting debugger will leave the world in a nice state
         * for us.
         */
-       ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "arm/hw_breakpoint:online",
-                               dbg_reset_online, NULL);
+       ret = cpuhp_setup_state_cpuslocked(CPUHP_AP_ONLINE_DYN,
+                                          "arm/hw_breakpoint:online",
+                                          dbg_reset_online, NULL);
        unregister_undef_hook(&debug_reg_hook);
        if (WARN_ON(ret < 0) || !cpumask_empty(&debug_err_mask)) {
                core_num_brps = 0;
                core_num_wrps = 0;
                if (ret > 0)
                        cpuhp_remove_state_nocalls(ret);
-               put_online_cpus();
+               cpus_read_unlock();
                return 0;
        }
 
@@ -1124,7 +1125,7 @@ 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();
+       cpus_read_unlock();
 
        /* Register PM notifiers. */
        pm_init();