Merge tag 'tty-3.12-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

[~andy/linux] / kernel / events / core.c

diff --git a/kernel/events/core.c b/kernel/events/core.c
index dd236b66ca3a8ef894386e7dcb8c7f02dbba34ae..cb4238e85b38e37886b27dd76351d2590a835924 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3660,6 +3660,26 @@ 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;
+
+       /* Allow new userspace to detect that bit 0 is deprecated */
+       userpg->cap_bit0_is_deprecated = 1;
+       userpg->size = offsetof(struct perf_event_mmap_page, __reserved);
+
+unlock:
+       rcu_read_unlock();
+}
+
 void __weak arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
 {
 }
@@ -4044,6 +4064,7 @@ again:
        ring_buffer_attach(event, rb);
        rcu_assign_pointer(event->rb, rb);
 
+       perf_event_init_userpage(event);
        perf_event_update_userpage(event);
 
 unlock: