futex_requeue_pi optimization

This patch provides the futex_requeue_pi functionality, which allows some
threads waiting on a normal futex to be requeued on the wait-queue of a
PI-futex.

This provides an optimization, already used for (normal) futexes, to be used
with the PI-futexes.

This optimization is currently used by the glibc in pthread_broadcast, when
using "normal" mutexes.  With futex_requeue_pi, it can be used with
PRIO_INHERIT mutexes too.

Signed-off-by: Pierre Peiffer <pierre.peiffer@bull.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
index dff27c471ea..338a9b489fb 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -156,7 +156,8 @@ asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
                         t = ktime_add(ktime_get(), t);
                 tp = &t;
         }
-        if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE)
+        if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE
+            || op == FUTEX_CMP_REQUEUE_PI)
                 val2 = (int) (unsigned long) utime;
 
         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);