(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; > > so > > 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.
