Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932920AbbHXJKe (ORCPT ); Mon, 24 Aug 2015 05:10:34 -0400 Received: from mx2.suse.de ([195.135.220.15]:58357 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932834AbbHXJKQ (ORCPT ); Mon, 24 Aug 2015 05:10:16 -0400 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Paul McKenney , Rusty Russell , Jiri Slaby Subject: [PATCH 3.12 62/82] rcu: Move lockless_dereference() out of rcupdate.h Date: Mon, 24 Aug 2015 11:09:22 +0200 Message-Id: <14a487b6fb4ca6c83b575d68ed605f499266a050.1440407339.git.jslaby@suse.cz> X-Mailer: git-send-email 2.5.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3186 Lines: 89 From: Peter Zijlstra 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 Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Rusty Russell Signed-off-by: Jiri Slaby --- 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 majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/