futex: rely on get_user_pages() for shared futexes

On the way of getting rid of the mmap_sem requirement for shared futexes,
start by relying on get_user_pages().

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/futex.h b/include/linux/futex.h
index 586ab56a3ec3..8f627b9ae2b1 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -164,6 +164,8 @@ union futex_key {
         } both;
 };
 
+#define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = NULL } }
+
 #ifdef CONFIG_FUTEX
 extern void exit_robust_list(struct task_struct *curr);
 extern void exit_pi_state_list(struct task_struct *curr);