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Message-ID: <20191104194528.GJ20975@paulmck-ThinkPad-P72>
Date: Mon, 4 Nov 2019 11:45:28 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Amol Grover <frextrite@...il.com>
Cc: Josh Triplett <josh@...htriplett.org>,
Steven Rostedt <rostedt@...dmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
Joel Fernandes <joel@...lfernandes.org>,
Jonathan Corbet <corbet@....net>, rcu@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-kernel-mentees@...ts.linuxfoundation.org,
Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] Documentation: RCU: whatisRCU: Fix formatting for
section 2
On Mon, Nov 04, 2019 at 10:46:41PM +0530, Amol Grover wrote:
> On Mon, Nov 04, 2019 at 07:03:28AM -0800, Paul E. McKenney wrote:
> > On Mon, Nov 04, 2019 at 07:03:15PM +0530, Amol Grover wrote:
> > > Convert RCU API method text to sub-headings and
> > > add hyperlink and superscript to 2 literary notes
> > > under rcu_dereference() section
> > >
> > > Signed-off-by: Amol Grover <frextrite@...il.com>
> >
> > Good stuff, but Phong Tran beat you to it. If you are suggesting
> > changes to that patch, please send a reply to her email, which
> > may be found here:
> >
> > https://lore.kernel.org/lkml/20191030233128.14997-1-tranmanphong@gmail.com/
> >
> > There are several options for replying to this email listed at the
> > bottom of that web page.
>
> Thank you Paul! And that is correct, I was suggesting changes to
> that patch. However, since that patch was already integrated into
> the `dev` branch, I mistakenly believed this patch could be sent
> independently. Sorry for the trouble, I'll re-send the patch the
> correct way.
It is of course only polite to include the author of the previous patch
on CC, both using the "Cc: Phong Tran <tranmanphong@...il.com>" tag
following your "Signed-off" by.
Thanx, Paul
> Thank you
> Amol
>
> >
> > > ---
> > > Documentation/RCU/whatisRCU.rst | 34 +++++++++++++++++++++++++++------
> > > 1 file changed, 28 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/Documentation/RCU/whatisRCU.rst b/Documentation/RCU/whatisRCU.rst
> > > index ae40c8bcc56c..3cf6e17d0065 100644
> > > --- a/Documentation/RCU/whatisRCU.rst
> > > +++ b/Documentation/RCU/whatisRCU.rst
> > > @@ -150,6 +150,7 @@ later. See the kernel docbook documentation for more info, or look directly
> > > at the function header comments.
> > >
> > > rcu_read_lock()
> > > +^^^^^^^^^^^^^^^
> > >
> > > void rcu_read_lock(void);
> > >
> > > @@ -164,6 +165,7 @@ rcu_read_lock()
> > > longer-term references to data structures.
> > >
> > > rcu_read_unlock()
> > > +^^^^^^^^^^^^^^^^^
> > >
> > > void rcu_read_unlock(void);
> > >
> > > @@ -172,6 +174,7 @@ rcu_read_unlock()
> > > read-side critical sections may be nested and/or overlapping.
> > >
> > > synchronize_rcu()
> > > +^^^^^^^^^^^^^^^^^
> > >
> > > void synchronize_rcu(void);
> > >
> > > @@ -225,6 +228,7 @@ synchronize_rcu()
> > > checklist.txt for some approaches to limiting the update rate.
> > >
> > > rcu_assign_pointer()
> > > +^^^^^^^^^^^^^^^^^^^^
> > >
> > > void rcu_assign_pointer(p, typeof(p) v);
> > >
> > > @@ -245,6 +249,7 @@ rcu_assign_pointer()
> > > the _rcu list-manipulation primitives such as list_add_rcu().
> > >
> > > rcu_dereference()
> > > +^^^^^^^^^^^^^^^^^
> > >
> > > typeof(p) rcu_dereference(p);
> > >
> > > @@ -279,8 +284,10 @@ rcu_dereference()
> > > if an update happened while in the critical section, and incur
> > > unnecessary overhead on Alpha CPUs.
> > >
> > > +.. _back_to_1:
> > > +
> > > Note that the value returned by rcu_dereference() is valid
> > > - only within the enclosing RCU read-side critical section [1].
> > > + only within the enclosing RCU read-side critical section |cs_1|.
> > > For example, the following is -not- legal::
> > >
> > > rcu_read_lock();
> > > @@ -298,15 +305,27 @@ rcu_dereference()
> > > it was acquired is just as illegal as doing so with normal
> > > locking.
> > >
> > > +.. _back_to_2:
> > > +
> > > As with rcu_assign_pointer(), an important function of
> > > rcu_dereference() is to document which pointers are protected by
> > > RCU, in particular, flagging a pointer that is subject to changing
> > > at any time, including immediately after the rcu_dereference().
> > > And, again like rcu_assign_pointer(), rcu_dereference() is
> > > typically used indirectly, via the _rcu list-manipulation
> > > - primitives, such as list_for_each_entry_rcu() [2].
> > > + primitives, such as list_for_each_entry_rcu() |entry_2|.
> > > +
> > > +.. |cs_1| raw:: html
> > > +
> > > + <a href="#cs"><sup>[1]</sup></a>
> > > +
> > > +.. |entry_2| raw:: html
> > >
> > > - [1] The variant rcu_dereference_protected() can be used outside
> > > + <a href="#entry"><sup>[2]</sup></a>
> > > +
> > > +.. _cs:
> > > +
> > > + \ :sup:`[1]`\ The variant rcu_dereference_protected() can be used outside
> > > of an RCU read-side critical section as long as the usage is
> > > protected by locks acquired by the update-side code. This variant
> > > avoids the lockdep warning that would happen when using (for
> > > @@ -317,15 +336,18 @@ rcu_dereference()
> > > a lockdep expression to indicate which locks must be acquired
> > > by the caller. If the indicated protection is not provided,
> > > a lockdep splat is emitted. See Documentation/RCU/Design/Requirements/Requirements.rst
> > > - and the API's code comments for more details and example usage.
> > > + and the API's code comments for more details and example usage. :ref:`back <back_to_1>`
> > > +
> > > +
> > > +.. _entry:
> > >
> > > - [2] If the list_for_each_entry_rcu() instance might be used by
> > > + \ :sup:`[2]`\ If the list_for_each_entry_rcu() instance might be used by
> > > update-side code as well as by RCU readers, then an additional
> > > lockdep expression can be added to its list of arguments.
> > > For example, given an additional "lock_is_held(&mylock)" argument,
> > > the RCU lockdep code would complain only if this instance was
> > > invoked outside of an RCU read-side critical section and without
> > > - the protection of mylock.
> > > + the protection of mylock. :ref:`back <back_to_2>`
> > >
> > > The following diagram shows how each API communicates among the
> > > reader, updater, and reclaimer.
> > > --
> > > 2.20.1
> > >
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