Messages in this thread | | | Subject | Re: [RFC PATCH v3 08/12] lib: vdso: allow arches to provide vdso data pointer | From | Christophe Leroy <> | Date | Thu, 16 Jan 2020 10:16:18 +0100 |
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Thomas, Andy,
Le 15/01/2020 à 07:15, Christophe Leroy a écrit : > > > Le 15/01/2020 à 00:06, Thomas Gleixner a écrit : >> Christophe Leroy <christophe.leroy@c-s.fr> writes: >>> static __maybe_unused int >>> +#ifdef VDSO_GETS_VD_PTR_FROM_ARCH >>> +__cvdso_clock_gettime_common(const struct vdso_data *vd, clockid_t >>> clock, >>> + struct __kernel_timespec *ts) >>> +{ >>> +#else >>> __cvdso_clock_gettime_common(clockid_t clock, struct >>> __kernel_timespec *ts) >>> { >>> const struct vdso_data *vd = __arch_get_vdso_data(); >>> +#endif >>> u32 msk; >> >> If we do that, then there is no point in propagating this to the inner >> functions. It's perfectly fine to have this distinction at the outermost >> level. > > In v2, I did it at the arch level (see > https://patchwork.ozlabs.org/patch/1214983/). Andy was concerned about > it being suboptimal for arches which (unlike powerpc) have PC related > data addressing mode. > > Wouldn't it be the same issue if doing it at the outermost level of > generic VDSO ?
Any opinion on this ?
From your point of view, what should I do: A/ __arch_get_vdso_data() handled entirely at arch level and arches handing over the vdso data pointer to generic C VDSO functions all the time (as in my v2 series) ? B/ Data pointer being handed over all the way up for arches wanting to do so, no changes at all for others (as in my v3 series) ? C/ __arch_get_vdso_data() being called at the outermost generic level for arches not interested in handling data pointer from the caller (as suggested by Thomas) ?
Andy, with A/ you were concerned about arches being able to do PC related accesses. Would it be an issue for C/ as well ? If not, I guess C/ would be cleaner than B/ allthought not as clean as A which doesn't add any #ifdefery at all.
Thanks Christophe
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