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Subject[PATCH 1/5] Add generic helpers for arch IPI function calls
Date
This adds kernel/smp.c which contains helpers for IPI function calls. In
addition to supporting the existing smp_call_function() in a more efficient
manner, it also adds a more scalable variant called smp_call_function_single()
for calling a given function on a single CPU only.

The core of this is based on the x86-64 patch from Nick Piggin.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
include/linux/smp.h | 30 +++++-
kernel/Makefile | 2 +-
kernel/smp.c | 316 +++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 345 insertions(+), 3 deletions(-)
create mode 100644 kernel/smp.c

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 55232cc..19b217e 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -7,9 +7,19 @@
*/

#include <linux/errno.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/cpumask.h>

extern void cpu_idle(void);

+struct call_single_data {
+ struct list_head list;
+ void (*func) (void *info);
+ void *info;
+ unsigned int flags;
+};
+
#ifdef CONFIG_SMP

#include <linux/preempt.h>
@@ -50,12 +60,27 @@ extern int __cpu_up(unsigned int cpunum);
extern void smp_cpus_done(unsigned int max_cpus);

/*
- * Call a function on all other processors
+ * Call a function on all other processors - arch exported functions
*/
int smp_call_function(void(*func)(void *info), void *info, int retry, int wait);
-
int smp_call_function_single(int cpuid, void (*func) (void *info), void *info,
int retry, int wait);
+void __smp_call_function_single(int cpuid, struct call_single_data *data);
+
+/*
+ * Generic helpers
+ */
+int generic_smp_call_function_single(int cpuid, void (*func) (void *info),
+ void *info, int wait,
+ void (*send_ipi)(int cpu));
+int generic_smp_call_function(void (*func) (void *info), void *info, int wait,
+ cpumask_t mask, void (*send_ipi)(cpumask_t));
+void generic_exec_single(int cpu, struct call_single_data *data,
+ void (*send_ipi)(int cpu));
+void generic_smp_call_function_single_interrupt(void);
+void generic_smp_call_function_interrupt(void);
+
+extern spinlock_t call_function_lock;

/*
* Call a function on all processors
@@ -92,6 +117,7 @@ static inline int up_smp_call_function(void (*func)(void *), void *info)
}
#define smp_call_function(func, info, retry, wait) \
(up_smp_call_function(func, info))
+
#define on_each_cpu(func,info,retry,wait) \
({ \
local_irq_disable(); \
diff --git a/kernel/Makefile b/kernel/Makefile
index 6c584c5..a805976 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -27,7 +27,7 @@ obj-$(CONFIG_RT_MUTEXES) += rtmutex.o
obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o
obj-$(CONFIG_RT_MUTEX_TESTER) += rtmutex-tester.o
obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
-obj-$(CONFIG_SMP) += cpu.o spinlock.o
+obj-$(CONFIG_SMP) += cpu.o spinlock.o smp.o
obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
obj-$(CONFIG_UID16) += uid16.o
diff --git a/kernel/smp.c b/kernel/smp.c
new file mode 100644
index 0000000..ab2da5c
--- /dev/null
+++ b/kernel/smp.c
@@ -0,0 +1,316 @@
+/*
+ * Generic helpers for smp ipi calls
+ *
+ * (C) Jens Axboe <jens.axboe@oracle.com> 2008
+ *
+ */
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/rcupdate.h>
+#include <linux/smp.h>
+
+static DEFINE_PER_CPU(struct call_single_queue, call_single_queue);
+static LIST_HEAD(call_function_queue);
+__cacheline_aligned_in_smp DEFINE_SPINLOCK(call_function_lock);
+
+enum {
+ CSD_FLAG_WAIT = 0x01,
+ CSD_FLAG_ALLOC = 0x02,
+ CSD_FLAG_FALLBACK = 0x04,
+};
+
+struct call_function_data {
+ struct call_single_data csd;
+ spinlock_t lock;
+ unsigned int refs;
+ cpumask_t cpumask;
+ struct rcu_head rcu_head;
+};
+
+struct call_single_queue {
+ struct list_head list;
+ spinlock_t lock;
+ int activated;
+};
+
+/*
+ * Fallback data to use, if the dyn allocation fails
+ */
+static struct call_function_data call_data_fallback;
+static unsigned long call_fallback_used;
+
+static int __cpuinit init_call_single_data(void)
+{
+ int i;
+
+ for_each_cpu_mask(i, cpu_possible_map) {
+ struct call_single_queue *q = &per_cpu(call_single_queue, i);
+
+ spin_lock_init(&q->lock);
+ INIT_LIST_HEAD(&q->list);
+ q->activated = 0;
+ }
+ return 0;
+}
+core_initcall(init_call_single_data);
+
+/*
+ * Insert a previously allocated call_single_data element for execution
+ * on the given CPU. data must already have ->func, ->info, and ->flags set.
+ */
+void generic_exec_single(int cpu, struct call_single_data *data,
+ void (*send_ipi)(int cpu))
+{
+ struct call_single_queue *dst;
+ unsigned long flags;
+ int wait = data->flags & CSD_FLAG_WAIT, ipi = 0;
+
+ INIT_LIST_HEAD(&data->list);
+
+ dst = &per_cpu(call_single_queue, cpu);
+ spin_lock_irqsave(&dst->lock, flags);
+ list_add_tail(&data->list, &dst->list);
+
+ smp_rmb();
+ if (!dst->activated) {
+ dst->activated = 1;
+ ipi = 1;
+ }
+
+ spin_unlock_irqrestore(&dst->lock, flags);
+
+ if (ipi)
+ send_ipi(cpu);
+
+ if (wait) {
+ /* Wait for response */
+ smp_rmb();
+ while (data->flags) {
+ cpu_relax();
+ smp_rmb();
+ }
+ }
+}
+
+/*
+ * Execute func(info) on the given cpu
+ */
+int generic_smp_call_function_single(int cpu, void (*func) (void *info),
+ void *info, int wait,
+ void (*send_ipi)(int cpu))
+{
+ unsigned long flags;
+ /* prevent preemption and reschedule on another processor */
+ int me = get_cpu();
+ int ret = 0;
+
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(wait && irqs_disabled());
+
+ if (cpu == me) {
+ local_irq_save(flags);
+ func(info);
+ local_irq_restore(flags);
+ } else {
+ struct call_single_data d;
+ struct call_single_data *data;
+
+ if (!wait) {
+ data = kmalloc(sizeof(*data), GFP_ATOMIC);
+ if (unlikely(!data)) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ data->flags = CSD_FLAG_ALLOC;
+ } else {
+ data = &d;
+ data->flags = CSD_FLAG_WAIT;
+ }
+
+ data->func = func;
+ data->info = info;
+ generic_exec_single(cpu, data, send_ipi);
+ }
+out:
+ put_cpu();
+ return ret;
+}
+
+static void rcu_free_call_data(struct rcu_head *head)
+{
+ struct call_function_data *cfd;
+
+ cfd = container_of(head, struct call_function_data, rcu_head);
+ kfree(cfd);
+}
+
+static void call_func_data_free(struct call_function_data *data)
+{
+ if (data->csd.flags & CSD_FLAG_ALLOC)
+ call_rcu(&data->rcu_head, rcu_free_call_data);
+ else
+ clear_bit_unlock(0, &call_fallback_used);
+}
+
+static struct call_function_data *call_func_data_alloc(gfp_t gfp, int wait_done)
+{
+ struct call_function_data *data;
+
+ data = kmalloc(sizeof(*data), gfp);
+ if (likely(data))
+ data->csd.flags = CSD_FLAG_ALLOC;
+ else {
+ while (test_and_set_bit_lock(0, &call_fallback_used))
+ cpu_relax();
+
+ data = &call_data_fallback;
+ data->csd.flags = CSD_FLAG_FALLBACK;
+ }
+
+ if (wait_done)
+ data->csd.flags |= CSD_FLAG_WAIT;
+
+ spin_lock_init(&data->lock);
+ return data;
+}
+
+/*
+ * Execute func(info) on the specified mask of CPUs
+ */
+int generic_smp_call_function(void (*func)(void *info), void *info, int wait,
+ cpumask_t mask,
+ void (*send_ipi)(cpumask_t mask))
+{
+ struct call_function_data *data;
+ cpumask_t allbutself;
+ int num_cpus;
+
+ /* Can deadlock when called with interrupts disabled */
+ WARN_ON(wait && irqs_disabled());
+
+ allbutself = cpu_online_map;
+ cpu_clear(smp_processor_id(), allbutself);
+ cpus_and(mask, mask, allbutself);
+ num_cpus = cpus_weight(mask);
+
+ if (!num_cpus)
+ return 0;
+
+ data = call_func_data_alloc(GFP_ATOMIC, wait);
+ data->csd.func = func;
+ data->csd.info = info;
+ data->refs = num_cpus;
+ data->cpumask = mask;
+
+ local_irq_disable();
+ while (!spin_trylock(&call_function_lock)) {
+ local_irq_enable();
+ cpu_relax();
+ local_irq_disable();
+ }
+
+ list_add_tail_rcu(&data->csd.list, &call_function_queue);
+ spin_unlock(&call_function_lock);
+ local_irq_enable();
+
+ /* Send a message to all CPUs in the map */
+ send_ipi(mask);
+
+ /* optionally wait for the CPUs to complete */
+ if (wait) {
+ smp_rmb();
+ while (data->csd.flags) {
+ cpu_relax();
+ smp_rmb();
+ }
+ call_func_data_free(data);
+ }
+
+ return 0;
+}
+
+/*
+ * Invoked by arch to handle an IPI for call function
+ */
+void generic_smp_call_function_interrupt(void)
+{
+ int cpu = smp_processor_id();
+ struct list_head *pos, *tmp;
+
+ list_for_each_safe_rcu(pos, tmp, &call_function_queue) {
+ struct call_function_data *data;
+ int refs;
+
+ data = list_entry(pos, struct call_function_data, csd.list);
+ if (!cpu_isset(cpu, data->cpumask))
+ continue;
+
+ data->csd.func(data->csd.info);
+ spin_lock(&data->lock);
+ WARN_ON(!cpu_isset(cpu, data->cpumask));
+ cpu_clear(cpu, data->cpumask);
+ WARN_ON(data->refs == 0);
+ data->refs--;
+ refs = data->refs;
+ spin_unlock(&data->lock);
+
+ if (refs)
+ continue;
+
+ WARN_ON(cpus_weight(data->cpumask));
+ spin_lock(&call_function_lock);
+ list_del_rcu(&data->csd.list);
+ spin_unlock(&call_function_lock);
+
+ if (data->csd.flags & CSD_FLAG_WAIT) {
+ smp_wmb();
+ data->csd.flags = 0;
+ } else
+ call_func_data_free(data);
+ }
+}
+
+/*
+ * Invoked by arch to handle an IPI for call function single
+ */
+void generic_smp_call_function_single_interrupt(void)
+{
+ struct call_single_queue *q = &__get_cpu_var(call_single_queue);
+ LIST_HEAD(list);
+
+ /*
+ * make sure list update is seen
+ */
+ smp_mb();
+ while (!list_empty(&q->list)) {
+ unsigned long flags;
+
+ spin_lock_irqsave(&q->lock, flags);
+ list_replace_init(&q->list, &list);
+ spin_unlock_irqrestore(&q->lock, flags);
+
+ while (!list_empty(&list)) {
+ struct call_single_data *data;
+
+ data = list_entry(list.next, struct call_single_data,
+ list);
+ list_del(&data->list);
+
+ data->func(data->info);
+ if (data->flags & CSD_FLAG_WAIT) {
+ smp_wmb();
+ data->flags = 0;
+ } else if (data->flags & CSD_FLAG_ALLOC)
+ kfree(data);
+ }
+
+ /*
+ * make sure list update is seen
+ */
+ smp_mb();
+ }
+
+ smp_wmb();
+ q->activated = 0;
+}
--
1.5.4.GIT


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