5 files changed, 238 insertions, 198 deletions

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index ce0efc6b26dc..ee9c21602228 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -64,7 +64,7 @@ static int raise_blk_irq(int cpu, struct request *rq)
                 data->info = rq;
                 data->flags = 0;
 
-                __smp_call_function_single(cpu, data);
+                __smp_call_function_single(cpu, data, 0);
                 return 0;
         }
 
diff --git a/include/linux/smp.h b/include/linux/smp.h
index 715196b09d67..00866d7fdf34 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -82,7 +82,8 @@ smp_call_function_mask(cpumask_t mask, void(*func)(void *info), void *info,
         return 0;
 }
 
-void __smp_call_function_single(int cpuid, struct call_single_data *data);
+void __smp_call_function_single(int cpuid, struct call_single_data *data,
+                                int wait);
 
 /*
  * Generic and arch helpers
diff --git a/kernel/sched.c b/kernel/sched.c
index 8e2558c2ba67..f1cd71918240 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1093,7 +1093,7 @@ static void hrtick_start(struct rq *rq, u64 delay)
         if (rq == this_rq()) {
                 hrtimer_restart(timer);
         } else if (!rq->hrtick_csd_pending) {
-                __smp_call_function_single(cpu_of(rq), &rq->hrtick_csd);
+                __smp_call_function_single(cpu_of(rq), &rq->hrtick_csd, 0);
                 rq->hrtick_csd_pending = 1;
         }
 }
diff --git a/kernel/smp.c b/kernel/smp.c
index bbedbb7efe32..7ad2262d2eca 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -2,40 +2,81 @@
  * 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/rculist.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
 #include <linux/smp.h>
+#include <linux/cpu.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);
+
+static struct {
+        struct list_head        queue;
+        spinlock_t              lock;
+} call_function __cacheline_aligned_in_smp =
+        {
+                .queue          = LIST_HEAD_INIT(call_function.queue),
+                .lock           = __SPIN_LOCK_UNLOCKED(call_function.lock),
+        };
 
 enum {
-        CSD_FLAG_WAIT           = 0x01,
-        CSD_FLAG_ALLOC          = 0x02,
-        CSD_FLAG_LOCK           = 0x04,
+        CSD_FLAG_LOCK           = 0x01,
 };
 
 struct call_function_data {
-        struct call_single_data csd;
-        spinlock_t lock;
-        unsigned int refs;
-        struct rcu_head rcu_head;
-        unsigned long cpumask_bits[];
+        struct call_single_data csd;
+        spinlock_t              lock;
+        unsigned int            refs;
+        cpumask_var_t           cpumask;
 };
 
 struct call_single_queue {
-        struct list_head list;
-        spinlock_t lock;
+        struct list_head        list;
+        spinlock_t              lock;
+};
+
+static DEFINE_PER_CPU(struct call_function_data, cfd_data) = {
+        .lock                   = __SPIN_LOCK_UNLOCKED(cfd_data.lock),
+};
+
+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 (!alloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
+                                cpu_to_node(cpu)))
+                        return NOTIFY_BAD;
+                break;
+
+#ifdef CONFIG_CPU_HOTPLUG
+        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,
 };
 
 static int __cpuinit init_call_single_data(void)
 {
+        void *cpu = (void *)(long)smp_processor_id();
         int i;
 
         for_each_possible_cpu(i) {
@@ -44,29 +85,63 @@ static int __cpuinit init_call_single_data(void)
                 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);
 
-static void csd_flag_wait(struct call_single_data *data)
+/*
+ * 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)
 {
-        /* Wait for response */
-        do {
-                if (!(data->flags & CSD_FLAG_WAIT))
-                        break;
+        while (data->flags & CSD_FLAG_LOCK)
                 cpu_relax();
-        } while (1);
+}
+
+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.
+ * 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)
+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);
-        int wait = data->flags & CSD_FLAG_WAIT, ipi;
         unsigned long flags;
+        int ipi;
 
         spin_lock_irqsave(&dst->lock, flags);
         ipi = list_empty(&dst->list);
@@ -74,24 +149,21 @@ static void generic_exec_single(int cpu, struct call_single_data *data)
         spin_unlock_irqrestore(&dst->lock, flags);
 
         /*
-         * Make the list addition visible before sending the ipi.
+         * 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...
          */
-        smp_mb();
-
         if (ipi)
                 arch_send_call_function_single_ipi(cpu);
 
         if (wait)
-                csd_flag_wait(data);
-}
-
-static void rcu_free_call_data(struct rcu_head *head)
-{
-        struct call_function_data *data;
-
-        data = container_of(head, struct call_function_data, rcu_head);
-
-        kfree(data);
+                csd_lock_wait(data);
 }
 
 /*
@@ -104,99 +176,83 @@ void generic_smp_call_function_interrupt(void)
         int cpu = get_cpu();
 
         /*
-         * It's ok to use list_for_each_rcu() here even though we may delete
-         * 'pos', since list_del_rcu() doesn't clear ->next
+         * 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
          */
-        rcu_read_lock();
-        list_for_each_entry_rcu(data, &call_function_queue, csd.list) {
+        list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
                 int refs;
 
-                if (!cpumask_test_cpu(cpu, to_cpumask(data->cpumask_bits)))
+                spin_lock(&data->lock);
+                if (!cpumask_test_cpu(cpu, data->cpumask)) {
+                        spin_unlock(&data->lock);
                         continue;
+                }
+                cpumask_clear_cpu(cpu, data->cpumask);
+                spin_unlock(&data->lock);
 
                 data->csd.func(data->csd.info);
 
                 spin_lock(&data->lock);
-                cpumask_clear_cpu(cpu, to_cpumask(data->cpumask_bits));
                 WARN_ON(data->refs == 0);
-                data->refs--;
-                refs = data->refs;
+                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);
 
                 if (refs)
                         continue;
 
-                spin_lock(&call_function_lock);
-                list_del_rcu(&data->csd.list);
-                spin_unlock(&call_function_lock);
-
-                if (data->csd.flags & CSD_FLAG_WAIT) {
-                        /*
-                         * serialize stores to data with the flag clear
-                         * and wakeup
-                         */
-                        smp_wmb();
-                        data->csd.flags &= ~CSD_FLAG_WAIT;
-                }
-                if (data->csd.flags & CSD_FLAG_ALLOC)
-                        call_rcu(&data->rcu_head, rcu_free_call_data);
+                csd_unlock(&data->csd);
         }
-        rcu_read_unlock();
 
         put_cpu();
 }
 
 /*
- * Invoked by arch to handle an IPI for call function single. Must be called
- * from the arch with interrupts disabled.
+ * 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);
 
-        /*
-         * Need to see other stores to list head for checking whether
-         * list is empty without holding q->lock
-         */
-        smp_read_barrier_depends();
-        while (!list_empty(&q->list)) {
-                unsigned int data_flags;
-
-                spin_lock(&q->lock);
-                list_replace_init(&q->list, &list);
-                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);
-
-                        if (data_flags & CSD_FLAG_WAIT) {
-                                smp_wmb();
-                                data->flags &= ~CSD_FLAG_WAIT;
-                        } else if (data_flags & CSD_FLAG_LOCK) {
-                                smp_wmb();
-                                data->flags &= ~CSD_FLAG_LOCK;
-                        } else if (data_flags & CSD_FLAG_ALLOC)
-                                kfree(data);
-                }
+        spin_lock(&q->lock);
+        list_replace_init(&q->list, &list);
+        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);
+
                 /*
-                 * See comment on outer loop
+                 * Unlocked CSDs are valid through generic_exec_single():
                  */
-                smp_read_barrier_depends();
+                if (data_flags & CSD_FLAG_LOCK)
+                        csd_unlock(data);
         }
 }
 
@@ -215,65 +271,45 @@ static DEFINE_PER_CPU(struct call_single_data, csd_data);
 int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
                              int wait)
 {
-        struct call_single_data d;
+        struct call_single_data d = {
+                .flags = 0,
+        };
         unsigned long flags;
-        /* prevent preemption and reschedule on another processor,
-           as well as CPU removal */
-        int me = get_cpu();
+        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 */
         WARN_ON(irqs_disabled());
 
-        if (cpu == me) {
+        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;
+        } else {
+                if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
+                        struct call_single_data *data = &d;
+
+                        if (!wait)
+                                data = &__get_cpu_var(csd_data);
 
-                if (!wait) {
-                        /*
-                         * We are calling a function on a single CPU
-                         * and we are not going to wait for it to finish.
-                         * We first try to allocate the data, but if we
-                         * fail, we fall back to use a per cpu data to pass
-                         * the information to that CPU. Since all callers
-                         * of this code will use the same data, we must
-                         * synchronize the callers to prevent a new caller
-                         * from corrupting the data before the callee
-                         * can access it.
-                         *
-                         * The CSD_FLAG_LOCK is used to let us know when
-                         * the IPI handler is done with the data.
-                         * The first caller will set it, and the callee
-                         * will clear it. The next caller must wait for
-                         * it to clear before we set it again. This
-                         * will make sure the callee is done with the
-                         * data before a new caller will use it.
-                         */
-                        data = kmalloc(sizeof(*data), GFP_ATOMIC);
-                        if (data)
-                                data->flags = CSD_FLAG_ALLOC;
-                        else {
-                                data = &per_cpu(csd_data, me);
-                                while (data->flags & CSD_FLAG_LOCK)
-                                        cpu_relax();
-                                data->flags = CSD_FLAG_LOCK;
-                        }
+                        csd_lock(data);
+
+                        data->func = func;
+                        data->info = info;
+                        generic_exec_single(cpu, data, wait);
                 } else {
-                        data = &d;
-                        data->flags = CSD_FLAG_WAIT;
+                        err = -ENXIO;   /* CPU not online */
                 }
-
-                data->func = func;
-                data->info = info;
-                generic_exec_single(cpu, data);
-        } else {
-                err = -ENXIO;   /* CPU not online */
         }
 
         put_cpu();
+
         return err;
 }
 EXPORT_SYMBOL(smp_call_function_single);
@@ -283,23 +319,26 @@ EXPORT_SYMBOL(smp_call_function_single);
  * @cpu: The CPU to run on.
  * @data: Pre-allocated and setup data structure
  *
- * 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.
- *
+ * 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)
+void __smp_call_function_single(int cpu, struct call_single_data *data,
+                                int wait)
 {
+        csd_lock(data);
+
         /* Can deadlock when called with interrupts disabled */
-        WARN_ON((data->flags & CSD_FLAG_WAIT) && irqs_disabled());
+        WARN_ON(wait && irqs_disabled());
 
-        generic_exec_single(cpu, data);
+        generic_exec_single(cpu, data, wait);
 }
 
-/* FIXME: Shim for archs using old arch_send_call_function_ipi API. */
+/* 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))
+# define arch_send_call_function_ipi_mask(maskp) \
+         arch_send_call_function_ipi(*(maskp))
 #endif
 
 /**
@@ -307,7 +346,8 @@ void __smp_call_function_single(int cpu, struct call_single_data *data)
  * @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.
+ * @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
@@ -318,27 +358,27 @@ void __smp_call_function_single(int cpu, struct call_single_data *data)
  * must be disabled when calling this function.
  */
 void smp_call_function_many(const struct cpumask *mask,
-                            void (*func)(void *), void *info,
-                            bool wait)
+                            void (*func)(void *), void *info, bool wait)
 {
         struct call_function_data *data;
         unsigned long flags;
-        int cpu, next_cpu;
+        int cpu, next_cpu, this_cpu = smp_processor_id();
 
         /* Can deadlock when called with interrupts disabled */
         WARN_ON(irqs_disabled());
 
-        /* So, what's a CPU they want?  Ignoring this one. */
+        /* So, what's a CPU they want? Ignoring this one. */
         cpu = cpumask_first_and(mask, cpu_online_mask);
-        if (cpu == smp_processor_id())
+        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 == smp_processor_id())
+        if (next_cpu == this_cpu)
                 next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
 
         /* Fastpath: do that cpu by itself. */
@@ -347,43 +387,40 @@ void smp_call_function_many(const struct cpumask *mask,
                 return;
         }
 
-        data = kmalloc(sizeof(*data) + cpumask_size(), GFP_ATOMIC);
-        if (unlikely(!data)) {
-                /* Slow path. */
-                for_each_online_cpu(cpu) {
-                        if (cpu == smp_processor_id())
-                                continue;
-                        if (cpumask_test_cpu(cpu, mask))
-                                smp_call_function_single(cpu, func, info, wait);
-                }
-                return;
-        }
+        data = &__get_cpu_var(cfd_data);
+        csd_lock(&data->csd);
 
-        spin_lock_init(&data->lock);
-        data->csd.flags = CSD_FLAG_ALLOC;
-        if (wait)
-                data->csd.flags |= CSD_FLAG_WAIT;
+        spin_lock_irqsave(&data->lock, flags);
         data->csd.func = func;
         data->csd.info = info;
-        cpumask_and(to_cpumask(data->cpumask_bits), mask, cpu_online_mask);
-        cpumask_clear_cpu(smp_processor_id(), to_cpumask(data->cpumask_bits));
-        data->refs = cpumask_weight(to_cpumask(data->cpumask_bits));
+        cpumask_and(data->cpumask, mask, cpu_online_mask);
+        cpumask_clear_cpu(this_cpu, data->cpumask);
+        data->refs = cpumask_weight(data->cpumask);
 
-        spin_lock_irqsave(&call_function_lock, flags);
-        list_add_tail_rcu(&data->csd.list, &call_function_queue);
-        spin_unlock_irqrestore(&call_function_lock, flags);
+        spin_lock(&call_function.lock);
+        /*
+         * 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);
 
         /*
          * 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(to_cpumask(data->cpumask_bits));
+        arch_send_call_function_ipi_mask(data->cpumask);
 
-        /* optionally wait for the CPUs to complete */
+        /* Optionally wait for the CPUs to complete */
         if (wait)
-                csd_flag_wait(&data->csd);
+                csd_lock_wait(&data->csd);
 }
 EXPORT_SYMBOL(smp_call_function_many);
 
@@ -391,7 +428,8 @@ 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.
+ * @wait: If true, wait (atomically) until function has completed
+ *        on other CPUs.
  *
  * Returns 0.
  *
@@ -407,26 +445,27 @@ int smp_call_function(void (*func)(void *), 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)
 {
-        spin_lock(&call_function_lock);
+        spin_lock(&call_function.lock);
 }
 
 void ipi_call_unlock(void)
 {
-        spin_unlock(&call_function_lock);
+        spin_unlock(&call_function.lock);
 }
 
 void ipi_call_lock_irq(void)
 {
-        spin_lock_irq(&call_function_lock);
+        spin_lock_irq(&call_function.lock);
 }
 
 void ipi_call_unlock_irq(void)
 {
-        spin_unlock_irq(&call_function_lock);
+        spin_unlock_irq(&call_function.lock);
 }
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 9041ea7948fe..ebe2a4d59f2c 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -496,7 +496,7 @@ static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softir
                 cp->flags = 0;
                 cp->priv = softirq;
 
-                __smp_call_function_single(cpu, cp);
+                __smp_call_function_single(cpu, cp, 0);
                 return 0;
         }
         return 1;