Messages in this thread | | | Date | Tue, 15 Mar 2016 10:36:21 -0700 | Subject | Re: [PATCH] nohz: Change tick_dep_mask from 'unsigned long' to 'unsigned int' | From | Linus Torvalds <> |
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On Tue, Mar 15, 2016 at 10:28 AM, Frederic Weisbecker <fweisbec@gmail.com> wrote: >> >> And wouldn't it be so nice if "thread_info->flags" would just be >> atomic_t too. Right now we use a mixture of bit-ops and ACCESS_ONCE() >> (and many codepaths then doing neither, and just accessing it >> directly, ignoring any races. >> >> Oh well. > > I can try that too while at it :-)
The real problem with thread_info->flags is that it's per-architecture, and people access that thing from assembly code.
So changing that is potentially really *very* painful. The patch itself is not likely too bad, but having confidence that everything was caught?
Nasty. It would probably be a very good cleanup, but I'm not sure how worthwhile it is considering the pain.
(The only good news is that any problem is likely to be *very* obvious. Switching the field to a 32-bit type on a big-endian machine and not catching some case will mean that people will check or modify the wrong flags, and you'd likely get breakage quite quickly)
Linus
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