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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-08-19 21:43:09 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-08-20 09:00:18 -0700 |
| commit | 65e6bf484c497f02d47a0faae69ee398cd59cfda (patch) | |
| tree | 644a86b779a196da7c050cde9de593c413e0cc1e | |
| parent | 80dcf60e6b97c7363971e7a0a788d8484d35f8a6 (diff) | |
| download | op-kernel-dev-65e6bf484c497f02d47a0faae69ee398cd59cfda.zip op-kernel-dev-65e6bf484c497f02d47a0faae69ee398cd59cfda.tar.gz | |
rcu: add comment stating that list_empty() applies to RCU-protected lists
Because list_empty() does not dereference any RCU-protected pointers, and
further does not pass such pointers to the caller (so that the caller
does not dereference them either), it is safe to use list_empty() on
RCU-protected lists. There is no need for a list_empty_rcu(). This
commit adds a comment stating this explicitly.
Requested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| -rw-r--r-- | include/linux/rculist.h | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/include/linux/rculist.h b/include/linux/rculist.h index c10b105..f31ef61 100644 --- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -10,6 +10,15 @@ #include <linux/rcupdate.h> /* + * Why is there no list_empty_rcu()? Because list_empty() serves this + * purpose. The list_empty() function fetches the RCU-protected pointer + * and compares it to the address of the list head, but neither dereferences + * this pointer itself nor provides this pointer to the caller. Therefore, + * it is not necessary to use rcu_dereference(), so that list_empty() can + * be used anywhere you would want to use a list_empty_rcu(). + */ + +/* * return the ->next pointer of a list_head in an rcu safe * way, we must not access it directly */ |
