From: Peter Zijlstra <[email protected]> 3.12-stable review patch. If anyone has any objections, please let me know.
=============== commit 0a04b0166929405cd833c1cc40f99e862b965ddc upstream. I want to use lockless_dereference() from seqlock.h, which would mean including rcupdate.h from it, however rcupdate.h already includes seqlock.h. Avoid this by moving lockless_dereference() into compiler.h. This is somewhat tricky since it uses smp_read_barrier_depends() which isn't available there, but its a CPP macro so we can get away with it. The alternative would be moving it into asm/barrier.h, but that would be updating each arch (I can do if people feel that is more appropriate). Cc: Paul McKenney <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Signed-off-by: Rusty Russell <[email protected]> Signed-off-by: Jiri Slaby <[email protected]> --- include/linux/compiler.h | 15 +++++++++++++++ include/linux/rcupdate.h | 15 --------------- 2 files changed, 15 insertions(+), 15 deletions(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 2472740d7ab2..4a3caa61a002 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -364,6 +364,21 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); */ #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x)) +/** + * lockless_dereference() - safely load a pointer for later dereference + * @p: The pointer to load + * + * Similar to rcu_dereference(), but for situations where the pointed-to + * object's lifetime is managed by something other than RCU. That + * "something other" might be reference counting or simple immortality. + */ +#define lockless_dereference(p) \ +({ \ + typeof(p) _________p1 = ACCESS_ONCE(p); \ + smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ + (_________p1); \ +}) + /* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */ #ifdef CONFIG_KPROBES # define __kprobes __attribute__((__section__(".kprobes.text"))) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 4912c953cab7..965725f957d9 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -555,21 +555,6 @@ static inline void rcu_preempt_sleep_check(void) } while (0) /** - * lockless_dereference() - safely load a pointer for later dereference - * @p: The pointer to load - * - * Similar to rcu_dereference(), but for situations where the pointed-to - * object's lifetime is managed by something other than RCU. That - * "something other" might be reference counting or simple immortality. - */ -#define lockless_dereference(p) \ -({ \ - typeof(p) _________p1 = ACCESS_ONCE(p); \ - smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ - (_________p1); \ -}) - -/** * rcu_access_pointer() - fetch RCU pointer with no dereferencing * @p: The pointer to read * -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
