* Rusty Russell (rusty@xxxxxxxxxxxxxxx) wrote: > On Wednesday 17 December 2008 10:31:55 Mathieu Desnoyers wrote: > > I think we have two different use-cases here : > > > > - local_t is useful as-is for things such as a tracer, which need to > > modify an element of data atomically wrt local interrupts. The > > atomic_long_t, in this case, is the correct fallback. > > - local_count_t could be used for fast counters. > > Hi Mathieu, > > Complete agreement. > > I guess I'm biassed towards local_t == counter version, something else > == nmi-safe version because that's what it was originally. Looking through > the tree, there are only 5 users: module, dmaengine and percpu_counter want > a counter, and tracing and x86 nmi.c want nmi-safe. There are several other > places I know of which want local_t-the-counter. > > I'll prepare a patch which adds nmi_safe_t, and see how it looks. There's > no amazing hurry on this, so I won't race to hit the merge window. > OK, But can we turn what you call "nmi_safe_t" into "local_atomic_t" then ? Because we have to specify that this type must only be used as part of per-cpu data with preemption disabled, and we also specify that it is atomic. Plus, nmi_safe_t does not make much sense on architectures without NMIs, where we sometimes disable interrupts to make the modification "atomic" wrt all other interrupts that can happen. Mathieu > Thanks! > Rusty. -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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