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    SubjectRe: [PATCH 1/2] irq_flags_t: intro and core annotations
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    On Sun, 2007-10-28 at 00:14 +0400, Alexey Dobriyan wrote:
    > On Sat, Oct 27, 2007 at 09:20:43PM +0200, Roman Zippel wrote:
    > > On Sun, 21 Oct 2007, Alexey Dobriyan wrote:
    > >
    > > > So far remedies were:
    > > > a) grep(1) -- obviously fragile. I tried at some point grepping for
    > > > spin_lock_irqsave(), found quite a few, but it became booooring quickly.
    > > > b) BUILD_BUG_ON(sizeof(flags) != sizeof(unsigned long)) -- was tried,
    > > > brutally broke some arches, survived one commit before revert :^)
    > > > Doesn't work on i386 where sizeof(unsigned int) == sizeof(unsigned long).
    > > >
    > > > So it would be nice to have something more robust.
    > >
    > > If it's just about the type checking, something like below should pretty
    > > much do the same.
    >
    > It won't catch, the following if both variables are unsigned long:
    >
    > spin_lock_irqsave(&lock, flags);
    > [stuff]
    > spin_unlock_irqrestore(&lock, foo->flags);
    >
    > It won't catch "static unsigned long flags;". With sparse, we can
    > eventually mark type as "on-stack only".

    > > +static __always_inline void __irq_flags_check(unsigned long *flags)
    > > +{
    + BUILD_BUG_ON(!__builtin_stack_addr(flags));
    > > +}
    > > +

    obviously gcc doesn't (yet) support that __builtin function, but you
    could make it work for sparse and define a dummy for gcc.

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