From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752679AbcHKJug (ORCPT ); Thu, 11 Aug 2016 05:50:36 -0400 Received: from s3.sipsolutions.net ([5.9.151.49]:51805 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752492AbcHKJub (ORCPT ); Thu, 11 Aug 2016 05:50:31 -0400 From: Johannes Berg To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , "Paul E . McKenney" , Ingo Molnar , Chris Wilson , Daniel Vetter , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, Johannes Berg Subject: [PATCH 2/2] locking/barriers: suppress sparse warnings in lockless_dereference() Date: Thu, 11 Aug 2016 11:50:22 +0200 Message-Id: <1470909022-687-2-git-send-email-johannes@sipsolutions.net> X-Mailer: git-send-email 2.8.1 In-Reply-To: <1470909022-687-1-git-send-email-johannes@sipsolutions.net> References: <1470909022-687-1-git-send-email-johannes@sipsolutions.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Johannes Berg After Peter's commit (see below) we get a lot of sparse warnings (one for every rcu_dereference, and more) since the expression here is assigning to the wrong address space. Instead of validating that 'p' is a pointer this way, instead make it fail compilation when it's not by using sizeof(*(p)). This will not cause any sparse warnings (tested, likely since the address space is irrelevant for sizeof), and will fail compilation when 'p' isn't a pointer type. Fixes: 331b6d8c7afc ("locking/barriers: Validate lockless_dereference() is used on a pointer type") Signed-off-by: Johannes Berg --- include/linux/compiler.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 1bb954842725..436aa4e42221 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -527,13 +527,13 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s * object's lifetime is managed by something other than RCU. That * "something other" might be reference counting or simple immortality. * - * The seemingly unused void * variable is to validate @p is indeed a pointer - * type. All pointer types silently cast to void *. + * The seemingly unused size_t variable is to validate @p is indeed a pointer + * type by making sure it can be dereferenced. */ #define lockless_dereference(p) \ ({ \ typeof(p) _________p1 = READ_ONCE(p); \ - __maybe_unused const void * const _________p2 = _________p1; \ + size_t __maybe_unused __size_of_ptr = sizeof(*(p)); \ smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ (_________p1); \ }) -- 2.8.1