Messages in this thread | | | Date | Mon, 13 Dec 2021 11:57:33 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 3/9] atomic: Introduce atomic_{inc,dec,dec_and_test}_overflow() |
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On Mon, Dec 13, 2021 at 10:06:01AM +0000, Mark Rutland wrote: > On Fri, Dec 10, 2021 at 05:16:21PM +0100, Peter Zijlstra wrote: > > In order to facilitate architecture support for refcount_t, introduce > > a number of new atomic primitives that have a uaccess style exception > > for overflow. > > > > Notably: > > > > atomic_inc_overflow(v, Label): > > > > increment and goto Label when the old value of v is zero or > > negative. > > > > atomic_dec_overflow(v, Label): > > > > decrement and goto Label when the new value of v is zero or > > negative > > > > atomic_dec_and_test_overflow(v, Label): > > > > decrement and return true when the result is zero and goto > > Label when the new value of v is negative > > Maybe it's worth adding these as comments in the fallback, which we have for a > few existing functions, e.g. > > | /** > | * arch_${atomic}_add_negative - add and test if negative > | * @i: integer value to add > | * @v: pointer of type ${atomic}_t > | * > | * Atomically adds @i to @v and returns true > | * if the result is negative, or false when > | * result is greater than or equal to zero. > | */ > | static __always_inline bool > | arch_${atomic}_add_negative(${int} i, ${atomic}_t *v) > | { > | return arch_${atomic}_add_return(i, v) < 0; > | } > > Not a big deal either way.
I can do that; but the whole ATOMIC*_OVERFLOW_OFFSET thing complicates all this somewhat. Still, let me try, I've gotta document that anyway..
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