[Linux-kernel-mentees] [PATCH] Documentation: RCU: whatisRCU: Fix formatting for section 2

Amol Grover frextrite at gmail.com
Mon Nov 4 17:31:56 UTC 2019


On Mon, Nov 04, 2019 at 05:15:34PM +0200, Jani Nikula wrote:
> On Mon, 04 Nov 2019, Amol Grover <frextrite at gmail.com> 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 at gmail.com>
> > ---
> >  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
> 
> Please don't use raw. It's ugly and error prone. We have some raw output
> for latex, but this would be the first for html.
> 
> What are you trying to achieve?

Hi Jani,
While going through the documentation I encountered a few footnotes (numbers
[1] and [2]) which referenced the actual footnote somewhere below the text.
They were particularly not straight-forward to find hence I decided to
link them to the footnote text which could be done using inline markup.
Then I tried to make them more appealing by converting to super-scripts
(the way they look like in books and websites). However, nested inline 
markup is not yet possible in reST hence I went with the html way to 
achieve the same. Too much?

Thank you
Amol

> 
> BR,
> Jani.
> 
> > +
> > +	<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.
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center


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