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Subject[PATCH 11/11] 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>
---
include/linux/perf_counter.h | 4 ++++
kernel/perf_counter.c | 30 +++++++++++++++++++-----------
2 files changed, 23 insertions(+), 11 deletions(-)
Index: linux-2.6/include/linux/perf_counter.h
===================================================================
--- linux-2.6.orig/include/linux/perf_counter.h
+++ linux-2.6/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;
Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/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 *co
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 *co
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
@@ -1134,6 +1138,14 @@ static struct perf_counter_context *find
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.
*/
@@ -1152,7 +1164,7 @@ static int perf_release(struct inode *in
mutex_unlock(&counter->mutex);
mutex_unlock(&ctx->mutex);

- kfree(counter);
+ call_rcu(&counter->rcu_head, free_counter_rcu);
put_context(ctx);

return 0;
@@ -1490,22 +1502,16 @@ static void perf_swcounter_ctx_event(str
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,
@@ -1843,6 +1849,7 @@ perf_counter_alloc(struct perf_counter_h

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);

@@ -1989,6 +1996,7 @@ __perf_counter_init_context(struct perf_
spin_lock_init(&ctx->lock);
mutex_init(&ctx->mutex);
INIT_LIST_HEAD(&ctx->counter_list);
+ INIT_LIST_HEAD(&ctx->event_list);
ctx->task = task;
}

--



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