On Thu, May 28, 2015 at 5:05 PM, Paul E. McKenney
<paul...@linux.vnet.ibm.com> wrote:
> On Thu, May 28, 2015 at 04:42:20PM -0400, Dan Streetman wrote:
>> On Thu, May 28, 2015 at 4:39 PM, <j...@joshtriplett.org> wrote:
>> > On Thu, May 28, 2015 at 04:35:27PM -0400, Dan Streetman wrote:
>> >> Add list_last_or_null_rcu(), to simplify getting the last entry from a
>> >> rcu-protected list. The standard list_last_entry() can't be used as it
>> >> is not rcu-protected; the list may be modified concurrently. And the
>> >> ->prev pointer can't be used, as only the ->next pointers are protected
>> >> by rcu.
>> >>
>> >> This simply iterates forward through the entire list, to get to the last
>> >> entry. If the list is empty, it returns NULL.
>> >>
>> >> Signed-off-by: Dan Streetman <ddstr...@ieee.org>
>> >
>> > The list iteration functions are macros because they introduce a loop
>> > with attached loop block. For this, is there any reason not to make it
>> > an inline function instead of a macro?
>>
>> true, there's no reason i can see not to make it inline, let me send
>> an updated patch.
>
> Hmmm... If we can now do type-generic inline functions, it might make
> sense to convert some of the others as well.
oh, ok. how do we do type-generic inline funcs? return void*?
>
> Thanx, Paul
>
>> >> include/linux/rculist.h | 21 +++++++++++++++++++++
>> >> 1 file changed, 21 insertions(+)
>> >>
>> >> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
>> >> index a18b16f..954fde5 100644
>> >> --- a/include/linux/rculist.h
>> >> +++ b/include/linux/rculist.h
>> >> @@ -293,6 +293,27 @@ static inline void list_splice_init_rcu(struct
>> >> list_head *list,
>> >> })
>> >>
>> >> /**
>> >> + * list_last_or_null_rcu - get the last element from a list
>> >> + * @ptr: the list head to take the element from.
>> >> + * @type: the type of the struct this is embedded in.
>> >> + * @member: the name of the list_head within the struct.
>> >> + *
>> >> + * Note that if the list is empty, it returns NULL.
>> >> + *
>> >> + * This primitive may safely run concurrently with the _rcu list-mutation
>> >> + * primitives such as list_add_rcu() as long as it's guarded by
>> >> rcu_read_lock().
>> >> + */
>> >> +#define list_last_or_null_rcu(ptr, type, member) \
>> >> +({ \
>> >> + struct list_head *__ptr = (ptr); \
>> >> + struct list_head *__last = __ptr; \
>> >> + struct list_head *__entry = list_next_rcu(__ptr); \
>> >> + for (; __entry != __ptr; __entry = list_next_rcu(__entry)) \
>> >> + __last = __entry; \
>> >> + likely(__ptr != __last) ? list_entry_rcu(__last, type, member) :
>> >> NULL; \
>> >> +})
>> >> +
>> >> +/**
>> >> * list_for_each_entry_rcu - iterate over rcu list of given type
>> >> * @pos: the type * to use as a loop cursor.
>> >> * @head: the head for your list.
>> >> --
>> >> 2.1.0
>> >>
>>
>
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