initial_commit

1 files changed, 703 insertions, 0 deletions

diff --git a/kernel/smp.c b/kernel/smp.c
new file mode 100644
index 00000000..fb67dfa8
--- /dev/null
+++ b/kernel/smp.c
@@ -0,0 +1,703 @@
+/*
+ * Generic helpers for smp ipi calls
+ *
+ * (C) Jens Axboe <jens.axboe@oracle.com> 2008
+ */
+#include <linux/rcupdate.h>
+#include <linux/rculist.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/gfp.h>
+#include <linux/smp.h>
+#include <linux/cpu.h>
+
+#ifdef CONFIG_USE_GENERIC_SMP_HELPERS
+static struct {
+	struct list_head	queue;
+	raw_spinlock_t		lock;
+} call_function __cacheline_aligned_in_smp =
+	{
+		.queue		= LIST_HEAD_INIT(call_function.queue),
+		.lock		= __RAW_SPIN_LOCK_UNLOCKED(call_function.lock),
+	};
+
+enum {
+	CSD_FLAG_LOCK		= 0x01,
+};
+
+struct call_function_data {
+	struct call_single_data	csd;
+	atomic_t		refs;
+	cpumask_var_t		cpumask;
+};
+
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
+
+struct call_single_queue {
+	struct list_head	list;
+	raw_spinlock_t		lock;
+};
+
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue);
+
+static int
+hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
+{
+	long cpu = (long)hcpu;
+	struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
+
+	switch (action) {
+	case CPU_UP_PREPARE:
+	case CPU_UP_PREPARE_FROZEN:
+		if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
+				cpu_to_node(cpu)))
+			return notifier_from_errno(-ENOMEM);
+		break;
+
+#ifdef CONFIG_HOTPLUG_CPU
+	case CPU_UP_CANCELED:
+	case CPU_UP_CANCELED_FROZEN:
+
+	case CPU_DEAD:
+	case CPU_DEAD_FROZEN:
+		free_cpumask_var(cfd->cpumask);
+		break;
+#endif
+	};
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
+	.notifier_call		= hotplug_cfd,
+};
+
+void __init call_function_init(void)
+{
+	void *cpu = (void *)(long)smp_processor_id();
+	int i;
+
+	for_each_possible_cpu(i) {
+		struct call_single_queue *q = &per_cpu(call_single_queue, i);
+
+		raw_spin_lock_init(&q->lock);
+		INIT_LIST_HEAD(&q->list);
+	}
+
+	hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
+	register_cpu_notifier(&hotplug_cfd_notifier);
+}
+
+/*
+ * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
+ *
+ * For non-synchronous ipi calls the csd can still be in use by the
+ * previous function call. For multi-cpu calls its even more interesting
+ * as we'll have to ensure no other cpu is observing our csd.
+ */
+static void csd_lock_wait(struct call_single_data *data)
+{
+	while (data->flags & CSD_FLAG_LOCK)
+		cpu_relax();
+}
+
+static void csd_lock(struct call_single_data *data)
+{
+	csd_lock_wait(data);
+	data->flags = CSD_FLAG_LOCK;
+
+	/*
+	 * prevent CPU from reordering the above assignment
+	 * to ->flags with any subsequent assignments to other
+	 * fields of the specified call_single_data structure:
+	 */
+	smp_mb();
+}
+
+static void csd_unlock(struct call_single_data *data)
+{
+	WARN_ON(!(data->flags & CSD_FLAG_LOCK));
+
+	/*
+	 * ensure we're all done before releasing data:
+	 */
+	smp_mb();
+
+	data->flags &= ~CSD_FLAG_LOCK;
+}
+
+/*
+ * Insert a previously allocated call_single_data element
+ * for execution on the given CPU. data must already have
+ * ->func, ->info, and ->flags set.
+ */
+static
+void generic_exec_single(int cpu, struct call_single_data *data, int wait)
+{
+	struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);
+	unsigned long flags;
+	int ipi;
+
+	raw_spin_lock_irqsave(&dst->lock, flags);
+	ipi = list_empty(&dst->list);
+	list_add_tail(&data->list, &dst->list);
+	raw_spin_unlock_irqrestore(&dst->lock, flags);
+
+	/*
+	 * The list addition should be visible before sending the IPI
+	 * handler locks the list to pull the entry off it because of
+	 * normal cache coherency rules implied by spinlocks.
+	 *
+	 * If IPIs can go out of order to the cache coherency protocol
+	 * in an architecture, sufficient synchronisation should be added
+	 * to arch code to make it appear to obey cache coherency WRT
+	 * locking and barrier primitives. Generic code isn't really
+	 * equipped to do the right thing...
+	 */
+	if (ipi)
+		arch_send_call_function_single_ipi(cpu);
+
+	if (wait)
+		csd_lock_wait(data);
+}
+
+/*
+ * Invoked by arch to handle an IPI for call function. Must be called with
+ * interrupts disabled.
+ */
+void generic_smp_call_function_interrupt(void)
+{
+	struct call_function_data *data;
+	int cpu = smp_processor_id();
+
+	/*
+	 * Shouldn't receive this interrupt on a cpu that is not yet online.
+	 */
+	WARN_ON_ONCE(!cpu_online(cpu));
+
+	/*
+	 * Ensure entry is visible on call_function_queue after we have
+	 * entered the IPI. See comment in smp_call_function_many.
+	 * If we don't have this, then we may miss an entry on the list
+	 * and never get another IPI to process it.
+	 */
+	smp_mb();
+
+	/*
+	 * It's ok to use list_for_each_rcu() here even though we may
+	 * delete 'pos', since list_del_rcu() doesn't clear ->next
+	 */
+	list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
+		int refs;
+		smp_call_func_t func;
+
+		/*
+		 * Since we walk the list without any locks, we might
+		 * see an entry that was completed, removed from the
+		 * list and is in the process of being reused.
+		 *
+		 * We must check that the cpu is in the cpumask before
+		 * checking the refs, and both must be set before
+		 * executing the callback on this cpu.
+		 */
+
+		if (!cpumask_test_cpu(cpu, data->cpumask))
+			continue;
+
+		smp_rmb();
+
+		if (atomic_read(&data->refs) == 0)
+			continue;
+
+		func = data->csd.func;		/* save for later warn */
+		func(data->csd.info);
+
+		/*
+		 * If the cpu mask is not still set then func enabled
+		 * interrupts (BUG), and this cpu took another smp call
+		 * function interrupt and executed func(info) twice
+		 * on this cpu.  That nested execution decremented refs.
+		 */
+		if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) {
+			WARN(1, "%pf enabled interrupts and double executed\n", func);
+			continue;
+		}
+
+		refs = atomic_dec_return(&data->refs);
+		WARN_ON(refs < 0);
+
+		if (refs)
+			continue;
+
+		WARN_ON(!cpumask_empty(data->cpumask));
+
+		raw_spin_lock(&call_function.lock);
+		list_del_rcu(&data->csd.list);
+		raw_spin_unlock(&call_function.lock);
+
+		csd_unlock(&data->csd);
+	}
+
+}
+
+/*
+ * Invoked by arch to handle an IPI for call function single. Must be
+ * called from the arch with interrupts disabled.
+ */
+void generic_smp_call_function_single_interrupt(void)
+{
+	struct call_single_queue *q = &__get_cpu_var(call_single_queue);
+	unsigned int data_flags;
+	LIST_HEAD(list);
+
+	/*
+	 * Shouldn't receive this interrupt on a cpu that is not yet online.
+	 */
+	WARN_ON_ONCE(!cpu_online(smp_processor_id()));
+
+	raw_spin_lock(&q->lock);
+	list_replace_init(&q->list, &list);
+	raw_spin_unlock(&q->lock);
+
+	while (!list_empty(&list)) {
+		struct call_single_data *data;
+
+		data = list_entry(list.next, struct call_single_data, list);
+		list_del(&data->list);
+
+		/*
+		 * 'data' can be invalid after this call if flags == 0
+		 * (when called through generic_exec_single()),
+		 * so save them away before making the call:
+		 */
+		data_flags = data->flags;
+
+		data->func(data->info);
+
+		/*
+		 * Unlocked CSDs are valid through generic_exec_single():
+		 */
+		if (data_flags & CSD_FLAG_LOCK)
+			csd_unlock(data);
+	}
+}
+
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
+
+/*
+ * smp_call_function_single - Run a function on a specific CPU
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait until function has completed on other CPUs.
+ *
+ * Returns 0 on success, else a negative status code.
+ */
+int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
+			     int wait)
+{
+	struct call_single_data d = {
+		.flags = 0,
+	};
+	unsigned long flags;
+	int this_cpu;
+	int err = 0;
+
+	/*
+	 * prevent preemption and reschedule on another processor,
+	 * as well as CPU removal
+	 */
+	this_cpu = get_cpu();
+
+	/*
+	 * Can deadlock when called with interrupts disabled.
+	 * We allow cpu's that are not yet online though, as no one else can
+	 * send smp call function interrupt to this cpu and as such deadlocks
+	 * can't happen.
+	 */
+	WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
+		     && !oops_in_progress);
+
+	if (cpu == this_cpu) {
+		local_irq_save(flags);
+		func(info);
+		local_irq_restore(flags);
+	} else {
+		if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
+			struct call_single_data *data = &d;
+
+			if (!wait)
+				data = &__get_cpu_var(csd_data);
+
+			csd_lock(data);
+
+			data->func = func;
+			data->info = info;
+			generic_exec_single(cpu, data, wait);
+		} else {
+			err = -ENXIO;	/* CPU not online */
+		}
+	}
+
+	put_cpu();
+
+	return err;
+}
+EXPORT_SYMBOL(smp_call_function_single);
+
+/*
+ * smp_call_function_any - Run a function on any of the given cpus
+ * @mask: The mask of cpus it can run on.
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait until function has completed.
+ *
+ * Returns 0 on success, else a negative status code (if no cpus were online).
+ * Note that @wait will be implicitly turned on in case of allocation failures,
+ * since we fall back to on-stack allocation.
+ *
+ * Selection preference:
+ *	1) current cpu if in @mask
+ *	2) any cpu of current node if in @mask
+ *	3) any other online cpu in @mask
+ */
+int smp_call_function_any(const struct cpumask *mask,
+			  smp_call_func_t func, void *info, int wait)
+{
+	unsigned int cpu;
+	const struct cpumask *nodemask;
+	int ret;
+
+	/* Try for same CPU (cheapest) */
+	cpu = get_cpu();
+	if (cpumask_test_cpu(cpu, mask))
+		goto call;
+
+	/* Try for same node. */
+	nodemask = cpumask_of_node(cpu_to_node(cpu));
+	for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
+	     cpu = cpumask_next_and(cpu, nodemask, mask)) {
+		if (cpu_online(cpu))
+			goto call;
+	}
+
+	/* Any online will do: smp_call_function_single handles nr_cpu_ids. */
+	cpu = cpumask_any_and(mask, cpu_online_mask);
+call:
+	ret = smp_call_function_single(cpu, func, info, wait);
+	put_cpu();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(smp_call_function_any);
+
+/**
+ * __smp_call_function_single(): Run a function on a specific CPU
+ * @cpu: The CPU to run on.
+ * @data: Pre-allocated and setup data structure
+ * @wait: If true, wait until function has completed on specified CPU.
+ *
+ * Like smp_call_function_single(), but allow caller to pass in a
+ * pre-allocated data structure. Useful for embedding @data inside
+ * other structures, for instance.
+ */
+void __smp_call_function_single(int cpu, struct call_single_data *data,
+				int wait)
+{
+	unsigned int this_cpu;
+	unsigned long flags;
+
+	this_cpu = get_cpu();
+	/*
+	 * Can deadlock when called with interrupts disabled.
+	 * We allow cpu's that are not yet online though, as no one else can
+	 * send smp call function interrupt to this cpu and as such deadlocks
+	 * can't happen.
+	 */
+	WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled()
+		     && !oops_in_progress);
+
+	if (cpu == this_cpu) {
+		local_irq_save(flags);
+		data->func(data->info);
+		local_irq_restore(flags);
+	} else {
+		csd_lock(data);
+		generic_exec_single(cpu, data, wait);
+	}
+	put_cpu();
+}
+
+/**
+ * smp_call_function_many(): Run a function on a set of other CPUs.
+ * @mask: The set of cpus to run on (only runs on online subset).
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait (atomically) until function has completed
+ *        on other CPUs.
+ *
+ * If @wait is true, then returns once @func has returned.
+ *
+ * You must not call this function with disabled interrupts or from a
+ * hardware interrupt handler or from a bottom half handler. Preemption
+ * must be disabled when calling this function.
+ */
+void smp_call_function_many(const struct cpumask *mask,
+			    smp_call_func_t func, void *info, bool wait)
+{
+	struct call_function_data *data;
+	unsigned long flags;
+	int refs, cpu, next_cpu, this_cpu = smp_processor_id();
+
+	/*
+	 * Can deadlock when called with interrupts disabled.
+	 * We allow cpu's that are not yet online though, as no one else can
+	 * send smp call function interrupt to this cpu and as such deadlocks
+	 * can't happen.
+	 */
+	WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
+		     && !oops_in_progress && !early_boot_irqs_disabled);
+
+	/* Try to fastpath.  So, what's a CPU they want? Ignoring this one. */
+	cpu = cpumask_first_and(mask, cpu_online_mask);
+	if (cpu == this_cpu)
+		cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
+
+	/* No online cpus?  We're done. */
+	if (cpu >= nr_cpu_ids)
+		return;
+
+	/* Do we have another CPU which isn't us? */
+	next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
+	if (next_cpu == this_cpu)
+		next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
+
+	/* Fastpath: do that cpu by itself. */
+	if (next_cpu >= nr_cpu_ids) {
+		smp_call_function_single(cpu, func, info, wait);
+		return;
+	}
+
+	data = &__get_cpu_var(cfd_data);
+	csd_lock(&data->csd);
+
+	/* This BUG_ON verifies our reuse assertions and can be removed */
+	BUG_ON(atomic_read(&data->refs) || !cpumask_empty(data->cpumask));
+
+	/*
+	 * The global call function queue list add and delete are protected
+	 * by a lock, but the list is traversed without any lock, relying
+	 * on the rcu list add and delete to allow safe concurrent traversal.
+	 * We reuse the call function data without waiting for any grace
+	 * period after some other cpu removes it from the global queue.
+	 * This means a cpu might find our data block as it is being
+	 * filled out.
+	 *
+	 * We hold off the interrupt handler on the other cpu by
+	 * ordering our writes to the cpu mask vs our setting of the
+	 * refs counter.  We assert only the cpu owning the data block
+	 * will set a bit in cpumask, and each bit will only be cleared
+	 * by the subject cpu.  Each cpu must first find its bit is
+	 * set and then check that refs is set indicating the element is
+	 * ready to be processed, otherwise it must skip the entry.
+	 *
+	 * On the previous iteration refs was set to 0 by another cpu.
+	 * To avoid the use of transitivity, set the counter to 0 here
+	 * so the wmb will pair with the rmb in the interrupt handler.
+	 */
+	atomic_set(&data->refs, 0);	/* convert 3rd to 1st party write */
+
+	data->csd.func = func;
+	data->csd.info = info;
+
+	/* Ensure 0 refs is visible before mask.  Also orders func and info */
+	smp_wmb();
+
+	/* We rely on the "and" being processed before the store */
+	cpumask_and(data->cpumask, mask, cpu_online_mask);
+	cpumask_clear_cpu(this_cpu, data->cpumask);
+	refs = cpumask_weight(data->cpumask);
+
+	/* Some callers race with other cpus changing the passed mask */
+	if (unlikely(!refs)) {
+		csd_unlock(&data->csd);
+		return;
+	}
+
+	raw_spin_lock_irqsave(&call_function.lock, flags);
+	/*
+	 * Place entry at the _HEAD_ of the list, so that any cpu still
+	 * observing the entry in generic_smp_call_function_interrupt()
+	 * will not miss any other list entries:
+	 */
+	list_add_rcu(&data->csd.list, &call_function.queue);
+	/*
+	 * We rely on the wmb() in list_add_rcu to complete our writes
+	 * to the cpumask before this write to refs, which indicates
+	 * data is on the list and is ready to be processed.
+	 */
+	atomic_set(&data->refs, refs);
+	raw_spin_unlock_irqrestore(&call_function.lock, flags);
+
+	/*
+	 * Make the list addition visible before sending the ipi.
+	 * (IPIs must obey or appear to obey normal Linux cache
+	 * coherency rules -- see comment in generic_exec_single).
+	 */
+	smp_mb();
+
+	/* Send a message to all CPUs in the map */
+	arch_send_call_function_ipi_mask(data->cpumask);
+
+	/* Optionally wait for the CPUs to complete */
+	if (wait)
+		csd_lock_wait(&data->csd);
+}
+EXPORT_SYMBOL(smp_call_function_many);
+
+/**
+ * smp_call_function(): Run a function on all other CPUs.
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait (atomically) until function has completed
+ *        on other CPUs.
+ *
+ * Returns 0.
+ *
+ * If @wait is true, then returns once @func has returned; otherwise
+ * it returns just before the target cpu calls @func.
+ *
+ * You must not call this function with disabled interrupts or from a
+ * hardware interrupt handler or from a bottom half handler.
+ */
+int smp_call_function(smp_call_func_t func, void *info, int wait)
+{
+	preempt_disable();
+	smp_call_function_many(cpu_online_mask, func, info, wait);
+	preempt_enable();
+
+	return 0;
+}
+EXPORT_SYMBOL(smp_call_function);
+
+void ipi_call_lock(void)
+{
+	raw_spin_lock(&call_function.lock);
+}
+
+void ipi_call_unlock(void)
+{
+	raw_spin_unlock(&call_function.lock);
+}
+
+void ipi_call_lock_irq(void)
+{
+	raw_spin_lock_irq(&call_function.lock);
+}
+
+void ipi_call_unlock_irq(void)
+{
+	raw_spin_unlock_irq(&call_function.lock);
+}
+#endif /* USE_GENERIC_SMP_HELPERS */
+
+/* Setup configured maximum number of CPUs to activate */
+unsigned int setup_max_cpus = NR_CPUS;
+EXPORT_SYMBOL(setup_max_cpus);
+
+
+/*
+ * Setup routine for controlling SMP activation
+ *
+ * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
+ * activation entirely (the MPS table probe still happens, though).
+ *
+ * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
+ * greater than 0, limits the maximum number of CPUs activated in
+ * SMP mode to <NUM>.
+ */
+
+void __weak arch_disable_smp_support(void) { }
+
+static int __init nosmp(char *str)
+{
+	setup_max_cpus = 0;
+	arch_disable_smp_support();
+
+	return 0;
+}
+
+early_param("nosmp", nosmp);
+
+/* this is hard limit */
+static int __init nrcpus(char *str)
+{
+	int nr_cpus;
+
+	get_option(&str, &nr_cpus);
+	if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
+		nr_cpu_ids = nr_cpus;
+
+	return 0;
+}
+
+early_param("nr_cpus", nrcpus);
+
+static int __init maxcpus(char *str)
+{
+	get_option(&str, &setup_max_cpus);
+	if (setup_max_cpus == 0)
+		arch_disable_smp_support();
+
+	return 0;
+}
+
+early_param("maxcpus", maxcpus);
+
+/* Setup number of possible processor ids */
+int nr_cpu_ids __read_mostly = NR_CPUS;
+EXPORT_SYMBOL(nr_cpu_ids);
+
+/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
+void __init setup_nr_cpu_ids(void)
+{
+	nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
+}
+
+/* Called by boot processor to activate the rest. */
+void __init smp_init(void)
+{
+	unsigned int cpu;
+
+	/* FIXME: This should be done in userspace --RR */
+	for_each_present_cpu(cpu) {
+		if (num_online_cpus() >= setup_max_cpus)
+			break;
+		if (!cpu_online(cpu))
+			cpu_up(cpu);
+	}
+
+	/* Any cleanup work */
+	printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus());
+	smp_cpus_done(setup_max_cpus);
+}
+
+/*
+ * Call a function on all processors.  May be used during early boot while
+ * early_boot_irqs_disabled is set.  Use local_irq_save/restore() instead
+ * of local_irq_disable/enable().
+ */
+int on_each_cpu(void (*func) (void *info), void *info, int wait)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	preempt_disable();
+	ret = smp_call_function(func, info, wait);
+	local_irq_save(flags);
+	func(info);
+	local_irq_restore(flags);
+	preempt_enable();
+	return ret;
+}
+EXPORT_SYMBOL(on_each_cpu);