1 files changed, 236 insertions, 196 deletions

diff --git a/kernel/smp.c b/kernel/smp.c
index bbedbb7efe3..858baac568e 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -2,40 +2,82 @@
  * 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/kernel.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 +86,63 @@ 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 +150,21 @@ 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);
 }