Commit 43850011 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

doc: Further updates to RCU's lockdep.rst 



This commit wordsmiths RCU's lockdep.rst.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 1b929c02

Documentation/RCU/lockdep.rst

+6 −7
Original line number Diff line number Diff line
@@ -69,9 +69,8 @@ checking of rcu_dereference() primitives: 
		value of the pointer itself, for example, against NULL.



The rcu_dereference_check() check expression can be any boolean

expression, but would normally include a lockdep expression.  However,

any boolean expression can be used.  For a moderately ornate example,

consider the following::

expression, but would normally include a lockdep expression.  For a

moderately ornate example, consider the following::



	file = rcu_dereference_check(fdt->fd[fd],

				     lockdep_is_held(&files->file_lock) ||
@@ -97,10 +96,10 @@ code, it could instead be written as follows:: 
					 atomic_read(&files->count) == 1);



This would verify cases #2 and #3 above, and furthermore lockdep would

complain if this was used in an RCU read-side critical section unless one

of these two cases held.  Because rcu_dereference_protected() omits all

barriers and compiler constraints, it generates better code than do the

other flavors of rcu_dereference().  On the other hand, it is illegal

complain even if this was used in an RCU read-side critical section unless

one of these two cases held.  Because rcu_dereference_protected() omits

all barriers and compiler constraints, it generates better code than do

the other flavors of rcu_dereference().  On the other hand, it is illegal

to use rcu_dereference_protected() if either the RCU-protected pointer

or the RCU-protected data that it points to can change concurrently.