Merge tag 'cpu-hotplug-3.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm (467a9e16) · Commits · 戴 / test

Documentation/cpu-hotplug.txt

+45 −0

Original line number	Diff line number	Diff line
		@@ -312,12 +312,57 @@ things will happen if a notifier in path sent a BAD notify code.
		Q: I don't see my action being called for all CPUs already up and running?
		A: Yes, CPU notifiers are called only when new CPUs are on-lined or offlined.
		If you need to perform some action for each cpu already in the system, then
		do this:

		for_each_online_cpu(i) {
		foobar_cpu_callback(&foobar_cpu_notifier, CPU_UP_PREPARE, i);
		foobar_cpu_callback(&foobar_cpu_notifier, CPU_ONLINE, i);
		}

		However, if you want to register a hotplug callback, as well as perform
		some initialization for CPUs that are already online, then do this:

		Version 1: (Correct)
		---------

		cpu_notifier_register_begin();

		for_each_online_cpu(i) {
		foobar_cpu_callback(&foobar_cpu_notifier,
		CPU_UP_PREPARE, i);
		foobar_cpu_callback(&foobar_cpu_notifier,
		CPU_ONLINE, i);
		}

		/* Note the use of the double underscored version of the API */
		__register_cpu_notifier(&foobar_cpu_notifier);

		cpu_notifier_register_done();

		Note that the following code is NOT the right way to achieve this,
		because it is prone to an ABBA deadlock between the cpu_add_remove_lock
		and the cpu_hotplug.lock.

		Version 2: (Wrong!)
		---------

		get_online_cpus();

		for_each_online_cpu(i) {
		foobar_cpu_callback(&foobar_cpu_notifier,
		CPU_UP_PREPARE, i);
		foobar_cpu_callback(&foobar_cpu_notifier,
		CPU_ONLINE, i);
		}

		register_cpu_notifier(&foobar_cpu_notifier);

		put_online_cpus();

		So always use the first version shown above when you want to register
		callbacks as well as initialize the already online CPUs.


		Q: If i would like to develop cpu hotplug support for a new architecture,
		what do i need at a minimum?
		A: The following are what is required for CPU hotplug infrastructure to work

arch/arm/kernel/hw_breakpoint.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -1073,6 +1073,8 @@ 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
		@@ -1089,6 +1091,7 @@ static int __init arch_hw_breakpoint_init(void)
		if (!cpumask_empty(&debug_err_mask)) {
		core_num_brps = 0;
		core_num_wrps = 0;
		cpu_notifier_register_done();
		return 0;
		}

		@@ -1108,7 +1111,10 @@ static int __init arch_hw_breakpoint_init(void)
		TRAP_HWBKPT, "breakpoint debug exception");

		/* Register hotplug and PM notifiers. */
		register_cpu_notifier(&dbg_reset_nb);
		__register_cpu_notifier(&dbg_reset_nb);

		cpu_notifier_register_done();

		pm_init();
		return 0;
		}

arch/arm/kvm/arm.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -1051,21 +1051,26 @@ int kvm_arch_init(void *opaque)
		}
		}

		cpu_notifier_register_begin();

		err = init_hyp_mode();
		if (err)
		goto out_err;

		err = register_cpu_notifier(&hyp_init_cpu_nb);
		err = __register_cpu_notifier(&hyp_init_cpu_nb);
		if (err) {
		kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
		goto out_err;
		}

		cpu_notifier_register_done();

		hyp_cpu_pm_init();

		kvm_coproc_table_init();
		return 0;
		out_err:
		cpu_notifier_register_done();
		return err;
		}

arch/arm64/kernel/debug-monitors.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -154,13 +154,17 @@ static struct notifier_block os_lock_nb = {

		static int debug_monitors_init(void)
		{
		cpu_notifier_register_begin();

		/* Clear the OS lock. */
		on_each_cpu(clear_os_lock, NULL, 1);
		isb();
		local_dbg_enable();

		/* Register hotplug handler. */
		register_cpu_notifier(&os_lock_nb);
		__register_cpu_notifier(&os_lock_nb);

		cpu_notifier_register_done();
		return 0;
		}
		postcore_initcall(debug_monitors_init);

arch/arm64/kernel/hw_breakpoint.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -913,6 +913,8 @@ static int __init arch_hw_breakpoint_init(void)
		pr_info("found %d breakpoint and %d watchpoint registers.\n",
		core_num_brps, core_num_wrps);

		cpu_notifier_register_begin();

		/*
		* Reset the breakpoint resources. We assume that a halting
		* debugger will leave the world in a nice state for us.
		@@ -927,7 +929,10 @@ static int __init arch_hw_breakpoint_init(void)
		TRAP_HWBKPT, "hw-watchpoint handler");

		/* Register hotplug notifier. */
		register_cpu_notifier(&hw_breakpoint_reset_nb);
		__register_cpu_notifier(&hw_breakpoint_reset_nb);

		cpu_notifier_register_done();

		/* Register cpu_suspend hw breakpoint restore hook */
		cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);

Admin message