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@xxxxxxxxx> --- 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
