Messages in this thread Patch in this message | | | From | Waiman Long <> | Subject | [PATCH-tip v6 05/22] futex: Add helpers to get & cmpxchg futex value without lock | Date | Wed, 22 Mar 2017 13:38:41 -0400 |
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Two new helper functions cmpxchg_futex_value() and get_futex_value() are added to access and change the futex value without the hash bucket lock. As a result, page fault is enabled and the page will be faulted in if not present yet.
Signed-off-by: Waiman Long <longman@redhat.com> --- kernel/futex.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/kernel/futex.c b/kernel/futex.c index 20aed91..9a27a79 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -805,6 +805,21 @@ static int get_futex_value_locked(u32 *dest, u32 __user *from) return ret ? -EFAULT : 0; } +/* + * The equivalents of the above cmpxchg_futex_value_locked() and + * get_futex_value_locked which are called without the hash bucket lock + * and so can have page fault enabled. + */ +static inline int cmpxchg_futex_value(u32 *curval, u32 __user *uaddr, + u32 uval, u32 newval) +{ + return futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval); +} + +static inline int get_futex_value(u32 *dest, u32 __user *from) +{ + return __get_user(*dest, from); +} /* * PI code: -- 1.8.3.1
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