lkml.org 
[lkml]   [2015]   [Jul]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH] thread_local_abi system call: caching current CPU number (x86)
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


\
 
 \ /
  Last update: 2015-07-17 19:21    [from the cache]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and my Meterkast|Read the blog