Hello!
This patch removes the unused list_for_each_safe_rcu() API. Any out-of-tree
uses of this interface can instead use list_for_each_rcu(), as noted in
the documentation updates. Builds, passes kernbench and LTP.
Signed-off-by: <[email protected]>
---
Documentation/RCU/checklist.txt | 8 ++++----
Documentation/RCU/whatisRCU.txt | 23 ++++++++++++++++++++++-
include/linux/list.h | 16 ----------------
3 files changed, 26 insertions(+), 21 deletions(-)
diff -urpNa -X dontdiff linux-2.6.14/Documentation/RCU/checklist.txt linux-2.6.14-RCUdoc/Documentation/RCU/checklist.txt
--- linux-2.6.14/Documentation/RCU/checklist.txt 2005-10-27 17:02:08.000000000 -0700
+++ linux-2.6.14-RCUdoc/Documentation/RCU/checklist.txt 2005-10-28 14:08:56.000000000 -0700
@@ -149,10 +149,10 @@ over a rather long period of time, but i
should be used in preference to call_rcu().
9. All RCU list-traversal primitives, which include
- list_for_each_rcu(), list_for_each_entry_rcu(),
- list_for_each_continue_rcu(), and list_for_each_safe_rcu(),
- must be within an RCU read-side critical section. RCU
- read-side critical sections are delimited by rcu_read_lock()
+ list_for_each_rcu(), list_for_each_entry_rcu(), and
+ list_for_each_continue_rcu() must be within an RCU read-side
+ critical section (or under the corresponding update-side lock).
+ RCU read-side critical sections are delimited by rcu_read_lock()
and rcu_read_unlock(), or by similar primitives such as
rcu_read_lock_bh() and rcu_read_unlock_bh().
diff -urpNa -X dontdiff linux-2.6.14/Documentation/RCU/whatisRCU.txt linux-2.6.14-RCUdoc/Documentation/RCU/whatisRCU.txt
--- linux-2.6.14/Documentation/RCU/whatisRCU.txt 2005-10-27 17:02:08.000000000 -0700
+++ linux-2.6.14-RCUdoc/Documentation/RCU/whatisRCU.txt 2005-10-28 14:40:47.000000000 -0700
@@ -768,7 +768,6 @@ RCU pointer/list traversal:
rcu_dereference
list_for_each_rcu (to be deprecated in favor of
list_for_each_entry_rcu)
- list_for_each_safe_rcu (deprecated, not used)
list_for_each_entry_rcu
list_for_each_continue_rcu (to be deprecated in favor of new
list_for_each_entry_continue_rcu)
@@ -798,6 +797,9 @@ RCU grace period:
See the comment headers in the source code (or the docbook generated
from them) for more information.
+Quick Quiz #4: Why isn't there a list_for_each_safe_rcu() and
+ a list_for_each_entry_safe_rcu()?
+
8. ANSWERS TO QUICK QUIZZES
@@ -892,6 +894,25 @@ Answer: Just as PREEMPT_RT permits pree
Besides, how does the computer know what pizza parlor
the human being went to???
+Quick Quiz #4: Why isn't there a list_for_each_safe_rcu() and
+ a list_for_each_entry_safe_rcu()?
+
+Answer: They are not needed. Any place you might be tempted
+ to use list_for_each_safe_rcu(), you should instead use
+ list_for_each_rcu(). Similarly, any place you might
+ want to use list_for_each_entry_safe_rcu() you should
+ instead use list_for_each_entry_rcu().
+
+ To see the reason for this substitution, consider that
+ the whole point of the _safe_ macros is to handle the
+ case where the body of the loop deletes the list
+ entry being examined. But RCU takes care of this deletion
+ case automatically, since any removed list element cannot
+ be freed until after all RCU read-side critical sections,
+ including the one containing the list macro, have completed.
+ Since RCU provides the safety, there is no need for a
+ special "safe" variant of the list macros.
+
ACKNOWLEDGEMENTS
diff -urpNa -X dontdiff linux-2.6.14/include/linux/list.h linux-2.6.14-RCUdoc/include/linux/list.h
--- linux-2.6.14/include/linux/list.h 2005-10-27 17:02:08.000000000 -0700
+++ linux-2.6.14-RCUdoc/include/linux/list.h 2005-10-28 14:40:52.000000000 -0700
@@ -452,22 +452,6 @@ static inline void list_splice_init(stru
pos = pos->next)
/**
- * list_for_each_safe_rcu - iterate over an rcu-protected list safe
- * against removal of list entry
- * @pos: the &struct list_head to use as a loop counter.
- * @n: another &struct list_head to use as temporary storage
- * @head: the head for your list.
- *
- * This list-traversal primitive may safely run concurrently with
- * the _rcu list-mutation primitives such as list_add_rcu()
- * as long as the traversal is guarded by rcu_read_lock().
- */
-#define list_for_each_safe_rcu(pos, n, head) \
- for (pos = (head)->next; \
- n = rcu_dereference(pos)->next, pos != (head); \
- pos = n)
-
-/**
* list_for_each_entry_rcu - iterate over rcu list of given type
* @pos: the type * to use as a loop counter.
* @head: the head for your list.
-
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