perf_counter: add an event_list

I noticed that the counter_list only includes top-level counters, thus
perf_swcounter_event() will miss sw-counters in groups.

Since perf_swcounter_event() also wants an RCU safe list, create a new
event_list that includes all counters and uses RCU list ops and use call_rcu
to free the counter structure.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index dfb4c7c..08c11a6 100644 (file)
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -187,6 +187,7 @@ struct file;
 struct perf_counter {
 #ifdef CONFIG_PERF_COUNTERS
        struct list_head                list_entry;
+       struct list_head                event_entry;
        struct list_head                sibling_list;
        struct perf_counter             *group_leader;
        const struct hw_perf_counter_ops *hw_ops;
@@ -220,6 +221,8 @@ struct perf_counter {
        struct perf_data                *irqdata;
        struct perf_data                *usrdata;
        struct perf_data                data[2];
+
+       struct rcu_head                 rcu_head;
 #endif
 };
 
@@ -243,6 +246,7 @@ struct perf_counter_context {
        struct mutex            mutex;
 
        struct list_head        counter_list;
+       struct list_head        event_list;
        int                     nr_counters;
        int                     nr_active;
        int                     is_active;

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index f9330d5..8d6ecfa 100644 (file)
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -22,6 +22,7 @@
 #include <linux/perf_counter.h>
 #include <linux/mm.h>
 #include <linux/vmstat.h>
+#include <linux/rculist.h>
 
 /*
  * Each CPU has a list of per CPU counters:
@@ -72,6 +73,8 @@ list_add_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
                list_add_tail(&counter->list_entry, &ctx->counter_list);
        else
                list_add_tail(&counter->list_entry, &group_leader->sibling_list);
+
+       list_add_rcu(&counter->event_entry, &ctx->event_list);
 }
 
 static void
@@ -80,6 +83,7 @@ list_del_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
        struct perf_counter *sibling, *tmp;
 
        list_del_init(&counter->list_entry);
+       list_del_rcu(&counter->event_entry);
 
        /*
         * If this was a group counter with sibling counters then
@@ -1133,6 +1137,14 @@ static struct perf_counter_context *find_get_context(pid_t pid, int cpu)
        return ctx;
 }
 
+static void free_counter_rcu(struct rcu_head *head)
+{
+       struct perf_counter *counter;
+
+       counter = container_of(head, struct perf_counter, rcu_head);
+       kfree(counter);
+}
+
 /*
  * Called when the last reference to the file is gone.
  */
@@ -1151,7 +1163,7 @@ static int perf_release(struct inode *inode, struct file *file)
        mutex_unlock(&counter->mutex);
        mutex_unlock(&ctx->mutex);
 
-       kfree(counter);
+       call_rcu(&counter->rcu_head, free_counter_rcu);
        put_context(ctx);
 
        return 0;
@@ -1491,22 +1503,16 @@ static void perf_swcounter_ctx_event(struct perf_counter_context *ctx,
                                     int nmi, struct pt_regs *regs)
 {
        struct perf_counter *counter;
-       unsigned long flags;
 
-       if (list_empty(&ctx->counter_list))
+       if (list_empty(&ctx->event_list))
                return;
 
-       spin_lock_irqsave(&ctx->lock, flags);
-
-       /*
-        * XXX: make counter_list RCU safe
-        */
-       list_for_each_entry(counter, &ctx->counter_list, list_entry) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(counter, &ctx->event_list, event_entry) {
                if (perf_swcounter_match(counter, event, regs))
                        perf_swcounter_add(counter, nr, nmi, regs);
        }
-
-       spin_unlock_irqrestore(&ctx->lock, flags);
+       rcu_read_unlock();
 }
 
 void perf_swcounter_event(enum hw_event_types event, u64 nr,
@@ -1846,6 +1852,7 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
 
        mutex_init(&counter->mutex);
        INIT_LIST_HEAD(&counter->list_entry);
+       INIT_LIST_HEAD(&counter->event_entry);
        INIT_LIST_HEAD(&counter->sibling_list);
        init_waitqueue_head(&counter->waitq);
 
@@ -1992,6 +1999,7 @@ __perf_counter_init_context(struct perf_counter_context *ctx,
        spin_lock_init(&ctx->lock);
        mutex_init(&ctx->mutex);
        INIT_LIST_HEAD(&ctx->counter_list);
+       INIT_LIST_HEAD(&ctx->event_list);
        ctx->task = task;
 }