Messages in this thread |  | | Date | Fri, 17 Jul 2015 10:03:00 -0700 | | From | Josh Triplett <> | | Subject | Re: [RFC PATCH] thread_local_abi system call: caching current CPU number (x86) |
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On Fri, Jul 17, 2015 at 10:49:19AM +0000, Ben Maurer wrote: > Mathieu Desnoyers wrote: > > Expose a new system call allowing threads to register a userspace memory > > area where to store the current CPU number. Scheduler migration sets the > > I really like that this approach makes it easier to add a per-thread interaction between userspace and the kernel in the future. > > >+ if (!tlap || t->thread_local_abi_len < > >+ offsetof(struct thread_local_abi, cpu) > >+ + sizeof(tlap->cpu)) > > Could you save a branch here by enforcing that thread_local_abi_len = 0 if thread_local_abi = null?
"saving a branch" doesn't seem like a good reason to do that; however, it *is* the convention across other calls: if you pass 0, the pointer is ignored, but if you pass non-zero, the pointer must be valid or you get -EFAULT (or an actual segfault).
- Josh Triplett
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