diff options
Diffstat (limited to 'Documentation/RCU/whatisRCU.txt')
| -rw-r--r-- | Documentation/RCU/whatisRCU.txt | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt index 7e1a8721637a..58ba05c4d97f 100644 --- a/Documentation/RCU/whatisRCU.txt +++ b/Documentation/RCU/whatisRCU.txt @@ -290,7 +290,7 @@ rcu_dereference() 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(). + primitives, such as list_for_each_entry_rcu() [2]. [1] The variant rcu_dereference_protected() can be used outside of an RCU read-side critical section as long as the usage is @@ -302,9 +302,17 @@ rcu_dereference() must prohibit. The rcu_dereference_protected() variant takes 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 RCU/Design/Requirements/Requirements.html + a lockdep splat is emitted. See Documentation/RCU/Design/Requirements/Requirements.rst and the API's code comments for more details and example usage. + [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 following diagram shows how each API communicates among the reader, updater, and reclaimer. @@ -630,7 +638,7 @@ been able to write-acquire the lock otherwise. The smp_mb__after_spinlock() promotes synchronize_rcu() to a full memory barrier in compliance with the "Memory-Barrier Guarantees" listed in: - Documentation/RCU/Design/Requirements/Requirements.html. + Documentation/RCU/Design/Requirements/Requirements.rst It is possible to nest rcu_read_lock(), since reader-writer locks may be recursively acquired. Note also that rcu_read_lock() is immune |