#include <linux/rcupdate.h>
#include <linux/rculist.h>
#include <linux/kernel.h>
-#include <linux/module.h>
+#include <linux/export.h>
#include <linux/percpu.h>
#include <linux/init.h>
+#include <linux/gfp.h>
#include <linux/smp.h>
#include <linux/cpu.h>
-static DEFINE_PER_CPU(struct call_single_queue, call_single_queue);
-
+#ifdef CONFIG_USE_GENERIC_SMP_HELPERS
static struct {
struct list_head queue;
- spinlock_t lock;
+ raw_spinlock_t lock;
} call_function __cacheline_aligned_in_smp =
{
.queue = LIST_HEAD_INIT(call_function.queue),
- .lock = __SPIN_LOCK_UNLOCKED(call_function.lock),
+ .lock = __RAW_SPIN_LOCK_UNLOCKED(call_function.lock),
};
enum {
struct call_function_data {
struct call_single_data csd;
- spinlock_t lock;
- unsigned int refs;
+ 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;
- spinlock_t lock;
+ raw_spinlock_t lock;
};
-static DEFINE_PER_CPU(struct call_function_data, cfd_data) = {
- .lock = __SPIN_LOCK_UNLOCKED(cfd_data.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)
case CPU_UP_PREPARE_FROZEN:
if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
cpu_to_node(cpu)))
- return NOTIFY_BAD;
+ return notifier_from_errno(-ENOMEM);
break;
-#ifdef CONFIG_CPU_HOTPLUG
+#ifdef CONFIG_HOTPLUG_CPU
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
.notifier_call = hotplug_cfd,
};
-static int __cpuinit init_call_single_data(void)
+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);
- spin_lock_init(&q->lock);
+ 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);
-
- return 0;
}
-early_initcall(init_call_single_data);
/*
* csd_lock/csd_unlock used to serialize access to per-cpu csd resources
unsigned long flags;
int ipi;
- spin_lock_irqsave(&dst->lock, flags);
+ raw_spin_lock_irqsave(&dst->lock, flags);
ipi = list_empty(&dst->list);
list_add_tail(&data->list, &dst->list);
- spin_unlock_irqrestore(&dst->lock, flags);
+ raw_spin_unlock_irqrestore(&dst->lock, flags);
/*
* The list addition should be visible before sending the IPI
void generic_smp_call_function_interrupt(void)
{
struct call_function_data *data;
- int cpu = get_cpu();
+ 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
*/
list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
int refs;
+ smp_call_func_t func;
- spin_lock(&data->lock);
- if (!cpumask_test_cpu(cpu, data->cpumask)) {
- spin_unlock(&data->lock);
+ /*
+ * 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;
}
- cpumask_clear_cpu(cpu, data->cpumask);
- spin_unlock(&data->lock);
-
- data->csd.func(data->csd.info);
-
- spin_lock(&data->lock);
- WARN_ON(data->refs == 0);
- refs = --data->refs;
- if (!refs) {
- spin_lock(&call_function.lock);
- list_del_rcu(&data->csd.list);
- spin_unlock(&call_function.lock);
- }
- spin_unlock(&data->lock);
+
+ 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);
}
- put_cpu();
}
/*
unsigned int data_flags;
LIST_HEAD(list);
- spin_lock(&q->lock);
+ /*
+ * 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);
- spin_unlock(&q->lock);
+ raw_spin_unlock(&q->lock);
while (!list_empty(&list)) {
struct call_single_data *data;
}
}
-static DEFINE_PER_CPU(struct call_single_data, csd_data);
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
/*
* smp_call_function_single - Run a function on a specific CPU
* @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. Note that @wait
- * will be implicitly turned on in case of allocation failures, since
- * we fall back to on-stack allocation.
+ * Returns 0 on success, else a negative status code.
*/
-int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
+int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
int wait)
{
struct call_single_data d = {
*/
this_cpu = get_cpu();
- /* Can deadlock when called with interrupts disabled */
- WARN_ON_ONCE(irqs_disabled() && !oops_in_progress);
+ /*
+ * 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);
}
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 another CPU
+ * __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
void __smp_call_function_single(int cpu, struct call_single_data *data,
int wait)
{
- csd_lock(data);
+ unsigned int this_cpu;
+ unsigned long flags;
- /* Can deadlock when called with interrupts disabled */
- WARN_ON_ONCE(wait && irqs_disabled() && !oops_in_progress);
+ 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);
- generic_exec_single(cpu, data, wait);
+ 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();
}
-/* Deprecated: shim for archs using old arch_send_call_function_ipi API. */
-
-#ifndef arch_send_call_function_ipi_mask
-# define arch_send_call_function_ipi_mask(maskp) \
- arch_send_call_function_ipi(*(maskp))
-#endif
-
/**
* 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).
* @wait: If true, wait (atomically) until function has completed
* on other CPUs.
*
- * If @wait is true, then returns once @func has returned. Note that @wait
- * will be implicitly turned on in case of allocation failures, since
- * we fall back to on-stack allocation.
+ * 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,
- void (*func)(void *), void *info, bool wait)
+ smp_call_func_t func, void *info, bool wait)
{
struct call_function_data *data;
unsigned long flags;
- int cpu, next_cpu, this_cpu = smp_processor_id();
+ int refs, cpu, next_cpu, this_cpu = smp_processor_id();
- /* Can deadlock when called with interrupts disabled */
- WARN_ON_ONCE(irqs_disabled() && !oops_in_progress);
+ /*
+ * 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);
- /* So, what's a CPU they want? Ignoring this one. */
+ /* 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);
data = &__get_cpu_var(cfd_data);
csd_lock(&data->csd);
- spin_lock_irqsave(&data->lock, flags);
+ /* 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);
- data->refs = cpumask_weight(data->cpumask);
+ refs = cpumask_weight(data->cpumask);
- spin_lock(&call_function.lock);
+ /* 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);
- spin_unlock(&call_function.lock);
-
- spin_unlock_irqrestore(&data->lock, flags);
+ /*
+ * 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.
* Returns 0.
*
* If @wait is true, then returns once @func has returned; otherwise
- * it returns just before the target cpu calls @func. In case of allocation
- * failure, @wait will be implicitly turned on.
+ * 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(void (*func)(void *), void *info, int wait)
+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);
void ipi_call_lock(void)
{
- spin_lock(&call_function.lock);
+ raw_spin_lock(&call_function.lock);
}
void ipi_call_unlock(void)
{
- spin_unlock(&call_function.lock);
+ raw_spin_unlock(&call_function.lock);
}
void ipi_call_lock_irq(void)
{
- spin_lock_irq(&call_function.lock);
+ raw_spin_lock_irq(&call_function.lock);
}
void ipi_call_unlock_irq(void)
{
- spin_unlock_irq(&call_function.lock);
+ 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);
projects / linux-flexiantxendom0-3.2.10.git / blobdiff