On Tue, May 01 2018, Paul E. McKenney wrote: > On Tue, May 01, 2018 at 01:11:29PM +1000, NeilBrown wrote: >> >> list_for_each_entry_from_rcu() is an RCU version of >> list_for_each_entry_from(). It walks a linked list under rcu >> protection, from a given start point. >> >> It is similar to list_for_each_entry_continue_rcu() but starts *at* >> the given position rather than *after* it. >> >> Naturally, the start point must be known to be in the list. >> >> Also update the documentation for list_for_each_entry_continue_rcu() >> to match the documentation for the new list_for_each_entry_from_rcu(), >> and add list_for_each_entry_from_rcu() and the already existing >> hlist_for_each_entry_from_rcu() to section 7 of whatisRCU.txt. >> >> Signed-off-by: NeilBrown <neilb@xxxxxxxx> > > I am guessing that it would be more convenient for you to carry this > with the patches using it, so: > > Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Thanks Paul, yes I do hope this patch will go in with the other NFS patches. I'll wait to see what Trond and Anna think before proceeding with anything myself. Thanks a lot, NeilBrown > > If not, please let me know. > > Thanx, Paul > >> --- >> Documentation/RCU/whatisRCU.txt | 2 ++ >> include/linux/rculist.h | 32 +++++++++++++++++++++++++++++++- >> 2 files changed, 33 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt >> index a27fbfb0efb8..b7d38bd212d2 100644 >> --- a/Documentation/RCU/whatisRCU.txt >> +++ b/Documentation/RCU/whatisRCU.txt >> @@ -814,11 +814,13 @@ RCU list traversal: >> list_next_rcu >> list_for_each_entry_rcu >> list_for_each_entry_continue_rcu >> + list_for_each_entry_from_rcu >> hlist_first_rcu >> hlist_next_rcu >> hlist_pprev_rcu >> hlist_for_each_entry_rcu >> hlist_for_each_entry_rcu_bh >> + hlist_for_each_entry_from_rcu >> hlist_for_each_entry_continue_rcu >> hlist_for_each_entry_continue_rcu_bh >> hlist_nulls_first_rcu >> diff --git a/include/linux/rculist.h b/include/linux/rculist.h >> index 127f534fec94..4786c2235b98 100644 >> --- a/include/linux/rculist.h >> +++ b/include/linux/rculist.h >> @@ -396,13 +396,43 @@ static inline void list_splice_tail_init_rcu(struct list_head *list, >> * @member: the name of the list_head within the struct. >> * >> * Continue to iterate over list of given type, continuing after >> - * the current position. >> + * the current position which must have been in the list when the RCU read >> + * lock was taken. >> + * This would typically require either that you obtained the node from a >> + * previous walk of the list in the same RCU read-side critical section, or >> + * that you held some sort of non-RCU reference (such as a reference count) >> + * to keep the node alive *and* in the list. >> + * >> + * This iterator is similar to list_for_each_entry_from_rcu() except >> + * this starts after the given position and that one starts at the given >> + * position. >> */ >> #define list_for_each_entry_continue_rcu(pos, head, member) \ >> for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \ >> &pos->member != (head); \ >> pos = list_entry_rcu(pos->member.next, typeof(*pos), member)) >> >> +/** >> + * list_for_each_entry_from_rcu - iterate over a list from current point >> + * @pos: the type * to use as a loop cursor. >> + * @head: the head for your list. >> + * @member: the name of the list_node within the struct. >> + * >> + * Iterate over the tail of a list starting from a given position, >> + * which must have been in the list when the RCU read lock was taken. >> + * This would typically require either that you obtained the node from a >> + * previous walk of the list in the same RCU read-side critical section, or >> + * that you held some sort of non-RCU reference (such as a reference count) >> + * to keep the node alive *and* in the list. >> + * >> + * This iterator is similar to list_for_each_entry_continue_rcu() except >> + * this starts from the given position and that one starts from the position >> + * after the given position. >> + */ >> +#define list_for_each_entry_from_rcu(pos, head, member) \ >> + for (; &(pos)->member != (head); \ >> + pos = list_entry_rcu(pos->member.next, typeof(*(pos)), member)) >> + >> /** >> * hlist_del_rcu - deletes entry from hash list without re-initialization >> * @n: the element to delete from the hash list. >> -- >> 2.14.0.rc0.dirty >>
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