Am 28.02.22 um 22:13 schrieb James Bottomley:
On Mon, 2022-02-28 at 21:56 +0100, Christian König wrote:
Am 28.02.22 um 21:42 schrieb James Bottomley:
On Mon, 2022-02-28 at 21:07 +0100, Christian König wrote:
Am 28.02.22 um 20:56 schrieb Linus Torvalds:
On Mon, Feb 28, 2022 at 4:19 AM Christian König christian.koenig@amd.com wrote: [SNIP] Anybody have any ideas?
I think we should look at the use cases why code is touching (pos) after the loop.
Just from skimming over the patches to change this and experience with the drivers/subsystems I help to maintain I think the primary pattern looks something like this:
list_for_each_entry(entry, head, member) { if (some_condition_checking(entry)) break; } do_something_with(entry);
Actually, we usually have a check to see if the loop found anything, but in that case it should something like
if (list_entry_is_head(entry, head, member)) { return with error; } do_somethin_with(entry);
Suffice? The list_entry_is_head() macro is designed to cope with the bogus entry on head problem.
That will work and is also what people already do.
The key problem is that we let people do the same thing over and over again with slightly different implementations.
Out in the wild I've seen at least using a separate variable, using a bool to indicate that something was found and just assuming that the list has an entry.
The last case is bogus and basically what can break badly.
Yes, I understand that. I'm saying we should replace that bogus checks of entry->something against some_value loop termination condition with the list_entry_is_head() macro. That should be a one line and fairly mechanical change rather than the explosion of code changes we seem to have in the patch series.
Yes, exactly that's my thinking as well.
Christian.
James