From: Linus Torvalds

Sent: 01 March 2022 23:03

On Tue, Mar 1, 2022 at 2:58 PM David Laight [off-list ref] wrote:

quoted

Can it be resolved by making:
#define list_entry_is_head(pos, head, member) ((pos) == NULL)
and double-checking that it isn't used anywhere else (except in
the list macros themselves).

Well, yes, except for the fact that then the name is entirely misleading...

And somebody possibly uses it together with list_first_entry() etc, so
it really is completely broken to mix that change with the list
traversal change.

Probably true :-(

Actually adding list_entry_not_found() as a synonym for
list_entry_is_head() and changing the 25ish places that
use it after a loop might work.

Once that is done the loop can be changed at the same time
as list_entry_not_found().
That won't affect the in-tree callers.
(and my out of tree modules don't use those lists - so I
don't care about that!)

Having said that there are so few users of list_entry_is_head()
it is reasonable to generate two new names.
One for use after list_for_each_entry() and one for list_next_entry().
Then the change all the call sites.
After that list_entry_is_head() can be deleted - breaking out of
tree compiles.
Finally list_for_each_entry() can be rewritten to set NULL
at the end of the list.

	David

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