Commit-ID: 137f61f6528f2bd552a75c59567d29db2857af97
Gitweb: https://git.kernel.org/tip/137f61f6528f2bd552a75c59567d29db2857af97
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 9 Oct 2017 10:30:58 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 4 Dec 2017 10:52:53 -0800
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: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
include/linux/rcupdate.h | 23 +++++++++++------------
1 file changed, 11 insertions(+), 12 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index a6ddc42..000432b 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -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
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