On Wed, Apr 14, 2021 at 03:32:04PM +0000, David Laight wrote: > From: Segher Boessenkool > > Sent: 14 April 2021 16:19 > ... > > > Could the kernel use GCC builtin atomic functions instead ? > > > > > > https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html > > > > Certainly that should work fine for the simpler cases that the atomic > > operations are meant to provide. But esp. for not-so-simple cases the > > kernel may require some behaviour provided by the existing assembler > > implementation, and not by the atomic builtins. > > > > I'm not saying this cannot work, just that some serious testing will be > > needed. If it works it should be the best of all worlds, so then it is > > a really good idea yes :-) > > I suspect they just add an extra layer of abstraction that makes it > even more difficult to verify and could easily get broken by a compiler > update (etc).
I would say it uses an existing facility, instead of creating a kernel- specific one. > The other issue is that the code needs to be correct with compiled > with (for example) -O0. > That could very easily break anything except the asm implementation > if additional memory accesses and/or increased code size cause grief. The compiler generates correct code. New versions of the compiler or old, -O0 or not, under any phase of the moon. Of course sometimes the compiler is broken, but there are pre-existing ways of dealing with that, and there is no reason at all to think this would break more often than random other code. Segher
