Messages in this thread | | | Date | Thu, 10 Apr 2008 11:31:41 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 0/3] clone64() and unshare64() system calls |
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sukadev@us.ibm.com wrote: > | > | I thought that the consensus was that adding a new system call was > | better than trying to force extensibility on to the existing > | non-extensible system call. > > There were couple of objections to extensible system calls like > sys_indirect() and to Pavel's approach. >
This is a very different thing, though. sys_indirect is pretty much a mechanism for having a sideband channel -- a second ABI -- into each and every system call, making it extremely hard to analyze what the full set of impact of a specific system call is. Worse, as it was being proposed to have been used, it would have set state variables inside the kernel in a very opaque manner.
> | But if we are adding a new system call, why not make the new one > | extensible to reduce the need for yet another new call in the future? > > hypothetically, can we make a variant of clone() extensible to the point > of requiring a copy_from_user() ?
The only issue is whether or not it's acceptable from a performance standpoint. clone() is reasonably expensive, though.
-hpa
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