On Wed, Sep 18, 2013 at 04:07:52PM -0400, Vince Weaver wrote:
> It would be nice if there was some way to detect this change; I liked the
> idea of a "cap_usr_fixed" bit.
How about we start using the version field for this? Arguably we should
have incremented that value every time we changed the thing but we might
as well start now.
---
diff --git a/kernel/events/core.c b/kernel/events/core.c
index dd236b6..c44d55c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3660,6 +3660,25 @@ static void calc_timer_values(struct perf_event *event,
*running = ctx_time - event->tstamp_running;
}
+static void perf_event_init_userpage(struct perf_event *event)
+{
+ struct perf_event_mmap_page *userpg;
+ struct ring_buffer *rb;
+
+ rcu_read_lock();
+ rb = rcu_dereference(event->rb);
+ if (!rb)
+ goto unlock;
+
+ userpg = rb->user_page;
+
+ userpg->version = 1;
+ userpg->compat_version = 0;
+
+unlock:
+ rcu_read_unlock();
+}
+
void __weak arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64
now)
{
}
@@ -4044,6 +4063,7 @@ static int perf_mmap(struct file *file, struct
vm_area_struct *vma)
ring_buffer_attach(event, rb);
rcu_assign_pointer(event->rb, rb);
+ perf_event_init_userpage(event);
perf_event_update_userpage(event);
unlock:
--
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