[PATCH] pcmcia: new suspend core

[pandora-kernel.git] / kernel / rcupdate.c

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 2559d4b..48d3bce 100644 (file)
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -116,6 +116,10 @@ void fastcall call_rcu(struct rcu_head *head,
        local_irq_restore(flags);
 }
 
+static atomic_t rcu_barrier_cpu_count;
+static struct semaphore rcu_barrier_sema;
+static struct completion rcu_barrier_completion;
+
 /**
  * call_rcu_bh - Queue an RCU for invocation after a quicker grace period.
  * @head: structure to be used for queueing the RCU updates.
@@ -153,6 +157,51 @@ void fastcall call_rcu_bh(struct rcu_head *head,
        local_irq_restore(flags);
 }
 
+/*
+ * Return the number of RCU batches processed thus far.  Useful
+ * for debug and statistics.
+ */
+long rcu_batches_completed(void)
+{
+       return rcu_ctrlblk.completed;
+}
+
+static void rcu_barrier_callback(struct rcu_head *notused)
+{
+       if (atomic_dec_and_test(&rcu_barrier_cpu_count))
+               complete(&rcu_barrier_completion);
+}
+
+/*
+ * Called with preemption disabled, and from cross-cpu IRQ context.
+ */
+static void rcu_barrier_func(void *notused)
+{
+       int cpu = smp_processor_id();
+       struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
+       struct rcu_head *head;
+
+       head = &rdp->barrier;
+       atomic_inc(&rcu_barrier_cpu_count);
+       call_rcu(head, rcu_barrier_callback);
+}
+
+/**
+ * rcu_barrier - Wait until all the in-flight RCUs are complete.
+ */
+void rcu_barrier(void)
+{
+       BUG_ON(in_interrupt());
+       /* Take cpucontrol semaphore to protect against CPU hotplug */
+       down(&rcu_barrier_sema);
+       init_completion(&rcu_barrier_completion);
+       atomic_set(&rcu_barrier_cpu_count, 0);
+       on_each_cpu(rcu_barrier_func, NULL, 0, 1);
+       wait_for_completion(&rcu_barrier_completion);
+       up(&rcu_barrier_sema);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier);
+
 /*
  * Invoke the completed RCU callbacks. They are expected to be in
  * a per-cpu list.
@@ -208,15 +257,23 @@ static void rcu_start_batch(struct rcu_ctrlblk *rcp, struct rcu_state *rsp,
 
        if (rcp->next_pending &&
                        rcp->completed == rcp->cur) {
-               /* Can't change, since spin lock held. */
-               cpus_andnot(rsp->cpumask, cpu_online_map, nohz_cpu_mask);
-
                rcp->next_pending = 0;
-               /* next_pending == 0 must be visible in __rcu_process_callbacks()
-                * before it can see new value of cur.
+               /*
+                * next_pending == 0 must be visible in
+                * __rcu_process_callbacks() before it can see new value of cur.
                 */
                smp_wmb();
                rcp->cur++;
+
+               /*
+                * Accessing nohz_cpu_mask before incrementing rcp->cur needs a
+                * Barrier  Otherwise it can cause tickless idle CPUs to be
+                * included in rsp->cpumask, which will extend graceperiods
+                * unnecessarily.
+                */
+               smp_mb();
+               cpus_andnot(rsp->cpumask, cpu_online_map, nohz_cpu_mask);
+
        }
 }
 
@@ -448,6 +505,7 @@ static struct notifier_block __devinitdata rcu_nb = {
  */
 void __init rcu_init(void)
 {
+       sema_init(&rcu_barrier_sema, 1);
        rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE,
                        (void *)(long)smp_processor_id());
        /* Register notifier for non-boot CPUs */
@@ -501,6 +559,7 @@ void synchronize_kernel(void)
 }
 
 module_param(maxbatch, int, 0);
+EXPORT_SYMBOL_GPL(rcu_batches_completed);
 EXPORT_SYMBOL(call_rcu);  /* WARNING: GPL-only in April 2006. */
 EXPORT_SYMBOL(call_rcu_bh);  /* WARNING: GPL-only in April 2006. */
 EXPORT_SYMBOL_GPL(synchronize_rcu);