Merge "smp: Allow booting a specific subset of CPUs" (b60fa5d7) · Commits · e / devices / android_kernel_sony_msm8994

Documentation/kernel-parameters.txt

+4 −0

Original line number	Diff line number	Diff line
		@@ -429,6 +429,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
		Format: <io>,<irq>,<mode>
		See header of drivers/net/hamradio/baycom_ser_hdx.c.

		boot_cpus= [SMP]
		Rather than attempting to online all possible CPUs at
		boot time, only online the specified set of CPUs.

		boot_delay= Milliseconds to delay each printk during boot.
		Values larger than 10 seconds (10000) are changed to
		no delay (0).

kernel/smp.c

+35 −1

Original line number	Diff line number	Diff line
		@@ -32,6 +32,10 @@ struct call_single_queue {
		raw_spinlock_t lock;
		};

		/* CPU mask indicating which CPUs to bring online during smp_init() */
		static bool have_boot_cpu_mask;
		static cpumask_var_t boot_cpu_mask;

		static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue);

		static int
		@@ -523,6 +527,19 @@ static int __init maxcpus(char *str)

		early_param("maxcpus", maxcpus);

		static int __init boot_cpus(char *str)
		{
		alloc_bootmem_cpumask_var(&boot_cpu_mask);
		if (cpulist_parse(str, boot_cpu_mask) < 0) {
		pr_warn("SMP: Incorrect boot_cpus cpumask\n");
		return -EINVAL;
		}
		have_boot_cpu_mask = true;
		return 0;
		}

		early_param("boot_cpus", boot_cpus);

		/* Setup number of possible processor ids */
		int nr_cpu_ids __read_mostly = NR_CPUS;
		EXPORT_SYMBOL(nr_cpu_ids);
		@@ -533,6 +550,21 @@ void __init setup_nr_cpu_ids(void)
		nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
		}

		/* Should the given CPU be booted during smp_init() ? */
		static inline bool boot_cpu(int cpu)
		{
		if (!have_boot_cpu_mask)
		return true;

		return cpumask_test_cpu(cpu, boot_cpu_mask);
		}

		static inline void free_boot_cpu_mask(void)
		{
		if (have_boot_cpu_mask) /* Allocated from boot_cpus() */
		free_bootmem_cpumask_var(boot_cpu_mask);
		}

		/* Called by boot processor to activate the rest. */
		void __init smp_init(void)
		{
		@@ -544,10 +576,12 @@ void __init smp_init(void)
		for_each_present_cpu(cpu) {
		if (num_online_cpus() >= setup_max_cpus)
		break;
		if (!cpu_online(cpu))
		if (!cpu_online(cpu) && boot_cpu(cpu))
		cpu_up(cpu);
		}

		free_boot_cpu_mask();

		/* Any cleanup work */
		printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus());
		smp_cpus_done(setup_max_cpus);