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McKenney" To: Amol Grover Cc: Phong Tran , corbet@lwn.net, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, joel@joelfernandes.org, linux-kernel-mentees@lists.linuxfoundation.org, madhuparnabhowmik04@gmail.com Subject: Re: [Linux-kernel-mentees] [PATCH] Documentation: RCU: arrayRCU: Converted arrayRCU.txt to arrayRCU.rst Message-ID: <20191105144515.GS20975@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20191028202417.13095-1-madhuparnabhowmik04@gmail.com> <20191105140411.GO20975@paulmck-ThinkPad-P72> <20191105143344.GA9069@workstation> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191105143344.GA9069@workstation> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 05, 2019 at 08:03:44PM +0530, Amol Grover wrote: > On Tue, Nov 05, 2019 at 06:04:11AM -0800, Paul E. McKenney wrote: > > On Tue, Nov 05, 2019 at 08:49:47PM +0700, Phong Tran wrote: > > > On 10/29/19 3:24 AM, madhuparnabhowmik04@gmail.com wrote: > > > > From: Madhuparna Bhowmik > > > > > > > > This patch converts arrayRCU from txt to rst format. > > > > arrayRCU.rst is also added in the index.rst file. > > > > > > > > Signed-off-by: Madhuparna Bhowmik > > > > --- > > > > .../RCU/{arrayRCU.txt => arrayRCU.rst} | 18 +++++++++++++----- > > > > Documentation/RCU/index.rst | 1 + > > > > 2 files changed, 14 insertions(+), 5 deletions(-) > > > > rename Documentation/RCU/{arrayRCU.txt => arrayRCU.rst} (91%) > > > > > > > > diff --git a/Documentation/RCU/arrayRCU.txt b/Documentation/RCU/arrayRCU.rst > > > > similarity index 91% > > > > rename from Documentation/RCU/arrayRCU.txt > > > > rename to Documentation/RCU/arrayRCU.rst > > > > index f05a9afb2c39..ed5ae24b196e 100644 > > > > --- a/Documentation/RCU/arrayRCU.txt > > > > +++ b/Documentation/RCU/arrayRCU.rst > > > > @@ -1,5 +1,7 @@ > > > > -Using RCU to Protect Read-Mostly Arrays > > > > +.. _array_rcu_doc: > > > > +Using RCU to Protect Read-Mostly Arrays > > > > +======================================= > > > > Although RCU is more commonly used to protect linked lists, it can > > > > also be used to protect arrays. Three situations are as follows: > > > > @@ -26,6 +28,7 @@ described in the following sections. > > > > > > It will be better to have the cross reference for each situation. > > > > > > Hash Tables > > > Static Arrays > > > Resizeable Arrays > > > > Madhuparna, could you please put a patch together creating these > > cross-references and handling Phong's comments below (probably > > by getting rid of the "." so that the resulting ":" doesn't look > > strange)? > > > > Then I will fold that patch into your original commit in -rcu and > > add Phong's Tested-by. > > > > Thanx, Paul > > > > > > Situation 1: Hash Tables > > > > +------------------------ > > > > Hash tables are often implemented as an array, where each array entry > > > > has a linked-list hash chain. Each hash chain can be protected by RCU > > > > @@ -34,6 +37,7 @@ to other array-of-list situations, such as radix trees. > > > > Situation 2: Static Arrays > > > > +-------------------------- > > > > Static arrays, where the data (rather than a pointer to the data) is > > > > located in each array element, and where the array is never resized, > > > > @@ -41,11 +45,13 @@ have not been used with RCU. Rik van Riel recommends using seqlock in > > > > this situation, which would also have minimal read-side overhead as long > > > > as updates are rare. > > > > -Quick Quiz: Why is it so important that updates be rare when > > > > - using seqlock? > > > > +Quick Quiz: > > > > + Why is it so important that updates be rare when using seqlock? > > > > +:ref:`Answer to Quick Quiz ` > > > > Situation 3: Resizeable Arrays > > > > +------------------------------ > > > > Use of RCU for resizeable arrays is demonstrated by the grow_ary() > > > > function formerly used by the System V IPC code. The array is used > > > > @@ -60,7 +66,7 @@ the remainder of the new, updates the ids->entries pointer to point to > > > > the new array, and invokes ipc_rcu_putref() to free up the old array. > > > > Note that rcu_assign_pointer() is used to update the ids->entries pointer, > > > > which includes any memory barriers required on whatever architecture > > > > -you are running on. > > > > +you are running on.:: > > > > > > a redundant ":" in here with html page. > > > > > > > > > > > > > > > > static int grow_ary(struct ipc_ids* ids, int newsize) > > > > { > > > > @@ -112,7 +118,7 @@ a simple check suffices. The pointer to the structure corresponding > > > > to the desired IPC object is placed in "out", with NULL indicating > > > > a non-existent entry. After acquiring "out->lock", the "out->deleted" > > > > flag indicates whether the IPC object is in the process of being > > > > -deleted, and, if not, the pointer is returned. > > > > +deleted, and, if not, the pointer is returned.:: > > > > > > same as above > > > > > > > > > Tested-by: Phong Tran > > > > > > Regards, > > > Phong. > > > > > > > struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id) > > > > { > > > > @@ -144,8 +150,10 @@ deleted, and, if not, the pointer is returned. > > > > return out; > > > > } > > > > +.. _answer_quick_quiz_seqlock: > > > > Answer to Quick Quiz: > > > > + Why is it so important that updates be rare when using seqlock? > > > > The reason that it is important that updates be rare when > > > > using seqlock is that frequent updates can livelock readers. > > > > diff --git a/Documentation/RCU/index.rst b/Documentation/RCU/index.rst > > > > index 5c99185710fa..8d20d44f8fd4 100644 > > > > --- a/Documentation/RCU/index.rst > > > > +++ b/Documentation/RCU/index.rst > > > > @@ -7,6 +7,7 @@ RCU concepts > > > > .. toctree:: > > > > :maxdepth: 3 > > > > + arrayRCU > > > > rcu > > > > listRCU > > > > UP > > > > > > _______________________________________________ > > Linux-kernel-mentees mailing list > > Linux-kernel-mentees@lists.linuxfoundation.org > > https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees > > Hey, > There are a few instances in the document where words are > emphasized. Example, -not- in the first paragraph. The > previous emphasis was correct wrt txt format, but this > could be converted to italicize/bold to keep up with the > reST format. Other than this and what Phong suggested, > everything looks good! > > Tested-by: Amol Grover Thank you, Amol! Madhuparna, could you please also include a fix to the "-not-" text-emphasis issue (and any other occurrences) that Amol located? I can then add both Phong's and Amol's Tested-by. Thanx, Paul