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Commit e5177ec7 authored by Michal Hocko's avatar Michal Hocko Committed by Paul E. McKenney
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rcu: Not necessary to pass rcu_read_lock_held() to rcu_dereference_protected() 



Since ca5ecddf (rcu: define __rcu address space modifier for sparse)
rcu_dereference_check() use rcu_read_lock_held() as a part of condition
automatically.  Therefore, callers of rcu_dereference_check() no longer
need to pass rcu_read_lock_held() to rcu_dereference_check().

Signed-off-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent e4cc1f22

Documentation/RCU/lockdep.txt

+4 −6
Original line number Original line Diff line number Diff line
@@ -48,13 +48,11 @@ checking of rcu_dereference() primitives: 
		value of the pointer itself, for example, against NULL.

		value of the pointer itself, for example, against NULL.





The rcu_dereference_check() check expression can be any boolean

The rcu_dereference_check() check expression can be any boolean

expression, but would normally include one of the rcu_read_lock_held()

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

family of functions and a lockdep expression.  However, any boolean

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

expression can be used.  For a moderately ornate example, consider

consider the following:

the following:





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

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

				     rcu_read_lock_held() ||

				     lockdep_is_held(&files->file_lock) ||

				     lockdep_is_held(&files->file_lock) ||

				     atomic_read(&files->count) == 1);

				     atomic_read(&files->count) == 1);
@@ -62,7 +60,7 @@ This expression picks up the pointer "fdt->fd[fd]" in an RCU-safe manner, 
and, if CONFIG_PROVE_RCU is configured, verifies that this expression

and, if CONFIG_PROVE_RCU is configured, verifies that this expression

is used in:

is used in:





1.	An RCU read-side critical section, or

1.	An RCU read-side critical section (implicit), or

2.	with files->file_lock held, or

2.	with files->file_lock held, or

3.	on an unshared files_struct.

3.	on an unshared files_struct.