Messages in this thread | | | Subject | Re: [thiscpuops upgrade 08/10] percpu: generic this_cpu_cmpxchg() and this_cpu_cmpxchg_double support | From | Eric Dumazet <> | Date | Fri, 26 Nov 2010 17:56:09 +0100 |
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Le vendredi 26 novembre 2010 à 17:51 +0100, Tejun Heo a écrit : > On 11/24/2010 12:51 AM, Christoph Lameter wrote: > > +/* > > + * cmpxchg_double replaces two adjacent scalars at once. The first parameter > > + * passed is a percpu pointer, not a scalar like the other this_cpu > > + * operations. This is so because the function operates on two scalars > > + * (must be of same size). A truth value is returned to indicate success or > > + * failure (since a double register result is difficult to handle). > > + * There is very limited hardware support for these operations. So only certain > > + * sizes may work. > > + */ > > +#define __this_cpu_generic_cmpxchg_double(pcp, oval1, oval2, nval1, nval2) \ > > Ah... this is scary. If it proves to be useful enough, sure, but > otherwise I'd like to avoid it. >
This is mandatory for several lockless algos, dont be afraid, its a single instruction ;)
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