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Commit 137f61f6 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Adjust read-side accessor comments for READ_ONCE() 



Now that READ_ONCE() implies smp_read_barrier_depends(), the commit
updates now-misleading comments to account for this change.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent b393e8b3

include/linux/rcupdate.h

+11 −12
Original line number Diff line number Diff line
@@ -433,12 +433,12 @@ static inline void rcu_preempt_sleep_check(void) { } 
 * @p: The pointer to read

 *

 * Return the value of the specified RCU-protected pointer, but omit the

 * smp_read_barrier_depends() and keep the READ_ONCE().  This is useful

 * when the value of this pointer is accessed, but the pointer is not

 * dereferenced, for example, when testing an RCU-protected pointer against

 * NULL.  Although rcu_access_pointer() may also be used in cases where

 * update-side locks prevent the value of the pointer from changing, you

 * should instead use rcu_dereference_protected() for this use case.

 * lockdep checks for being in an RCU read-side critical section.  This is

 * useful when the value of this pointer is accessed, but the pointer is

 * not dereferenced, for example, when testing an RCU-protected pointer

 * against NULL.  Although rcu_access_pointer() may also be used in cases

 * where update-side locks prevent the value of the pointer from changing,

 * you should instead use rcu_dereference_protected() for this use case.

 *

 * It is also permissible to use rcu_access_pointer() when read-side

 * access to the pointer was removed at least one grace period ago, as
@@ -521,12 +521,11 @@ static inline void rcu_preempt_sleep_check(void) { } 
 * @c: The conditions under which the dereference will take place

 *

 * Return the value of the specified RCU-protected pointer, but omit

 * both the smp_read_barrier_depends() and the READ_ONCE().  This

 * is useful in cases where update-side locks prevent the value of the

 * pointer from changing.  Please note that this primitive does *not*

 * prevent the compiler from repeating this reference or combining it

 * with other references, so it should not be used without protection

 * of appropriate locks.

 * the READ_ONCE().  This is useful in cases where update-side locks

 * prevent the value of the pointer from changing.  Please note that this

 * primitive does *not* prevent the compiler from repeating this reference

 * or combining it with other references, so it should not be used without

 * protection of appropriate locks.

 *

 * This function is only for update-side use.  Using this function

 * when protected only by rcu_read_lock() will result in infrequent