| From | Linus Torvalds <> | Date | Tue, 12 Feb 2019 09:38:42 -0800 | Subject | Re: [PATCH 02/32] locking/lockdep: Introduce struct lock_usage |
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On Tue, Feb 12, 2019 at 9:14 AM Frederic Weisbecker <frederic@kernel.org> wrote: > > +static u64 lock_usage_mask(struct lock_usage *usage) > +{ > + return BIT(usage->bit); > +}
More insane "u64" - and it's *incorrect* too.
#define BIT(nr) (1UL << (nr))
fundamentally means that "BIT()" can only work on up to "unsigned long".
So this odd use of u64 seems to be a disease. It only uses more memory (and more CPU) for no obvious reason.
u64 is not some "default type". It's expensive and shouldn't be used unless you have a *reason* for it.
Linus
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