(Adding Julia Lawall)
On Wed, 2018-04-11 at 09:29 -0700, Andrew Morton wrote:
> We already have some 500 bools-in-structs
I got at least triple that only in include/
so I expect there are at probably an order
of magnitude more than 500 in the kernel.
I suppose some cocci script could count the
actual number of instances. A regex can not.
> and the owners of that code will
> be wondering whether they should change them, and whether they should
> apply those remove-bool-in-struct patches which someone sent them.
Which is why the warning is --strict only
> So... can we please get some clarity here?
> (ooh, https://lkml.org/lkml/2017/11/21/384 is working this morning)
> hm, Linus suggests that instead of using
> bool mybool;
> we should use
> unsigned mybool:1;
> However that introduces the risk that alterations of mybool will use
> nonatomic rmw operations.
> unsigned myboolA:1;
> unsigned myboolB:1;
> foo->myboolA = 1;
> could scribble on concurrent alterations of foo->myboolB. I think.
Without barriers, that could happen anyway.
To me, the biggest problem with conversions
from bool to bitfield is logical. ie:
unsigned int.singlebitfield = 4;
is not the same result as
bool = 4;
because of implicit truncation vs boolean conversion
so a direct change of bool use in structs to unsigned
would also require logic analysis.