From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759509Ab2JSQsm (ORCPT ); Fri, 19 Oct 2012 12:48:42 -0400 Received: from smtp.outflux.net ([198.145.64.163]:49496 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759114Ab2JSQsk (ORCPT ); Fri, 19 Oct 2012 12:48:40 -0400 Date: Fri, 19 Oct 2012 09:48:30 -0700 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Dipankar Sarma , "Paul E. McKenney" , Rob Landley , linux-doc@vger.kernel.org Subject: [PATCH] RCU: update docs to include kfree_rcu() Message-ID: <20121019164830.GA4896@www.outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mention kfree_rcu() in the call_rcu() section. Additionally fix the example code for list replacement that used the wrong structure element. Signed-off-by: Kees Cook --- Documentation/RCU/listRCU.txt | 2 +- Documentation/RCU/whatisRCU.txt | 13 +++++++++++-- 2 files changed, 12 insertions(+), 3 deletions(-) diff --git a/Documentation/RCU/listRCU.txt b/Documentation/RCU/listRCU.txt index 4349c14..adb5a37 100644 --- a/Documentation/RCU/listRCU.txt +++ b/Documentation/RCU/listRCU.txt @@ -205,7 +205,7 @@ RCU ("read-copy update") its name. The RCU code is as follows: audit_copy_rule(&ne->rule, &e->rule); ne->rule.action = newaction; ne->rule.file_count = newfield_count; - list_replace_rcu(e, ne); + list_replace_rcu(&e->list, &ne->list); call_rcu(&e->rcu, audit_free_rule); return 0; } diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt index bf0f6de..160ac55 100644 --- a/Documentation/RCU/whatisRCU.txt +++ b/Documentation/RCU/whatisRCU.txt @@ -499,6 +499,8 @@ The foo_reclaim() function might appear as follows: { struct foo *fp = container_of(rp, struct foo, rcu); + foo_cleanup(fp->a); + kfree(fp); } @@ -521,6 +523,12 @@ o Use call_rcu() -after- removing a data element from an read-side critical sections that might be referencing that data item. +If the callback for call_rcu() is not doing anything more than calling +kfree() on the structure, you can use kfree_rcu() instead of call_rcu() +to avoid having to write your own callback: + + kfree_rcu(old_fp, rcu); + Again, see checklist.txt for additional rules governing the use of RCU. @@ -773,8 +781,8 @@ a single atomic update, converting to RCU will require special care. Also, the presence of synchronize_rcu() means that the RCU version of delete() can now block. If this is a problem, there is a callback-based -mechanism that never blocks, namely call_rcu(), that can be used in -place of synchronize_rcu(). +mechanism that never blocks, namely call_rcu() or kfree_rcu(), that can +be used in place of synchronize_rcu(). 7. FULL LIST OF RCU APIs @@ -813,6 +821,7 @@ RCU: Critical sections Grace period Barrier rcu_read_unlock synchronize_rcu rcu_dereference synchronize_rcu_expedited call_rcu + kfree_rcu bh: Critical sections Grace period Barrier -- 1.7.9.5 -- Kees Cook Chrome OS Security