Messages in this thread | | | Date | Tue, 15 Mar 2016 09:30:49 -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 5:15 AM, Ingo Molnar <mingo@kernel.org> wrote: > > Hm, so the problem I did not consider is the following: > > triton:~/tip> git grep tick_dep_mask kernel | grep _bit > kernel/time/tick-sched.c: clear_bit(bit, &ts->tick_dep_mask); > kernel/time/tick-sched.c: clear_bit(bit, &tsk->tick_dep_mask); > kernel/time/tick-sched.c: clear_bit(bit, &sig->tick_dep_mask);
Ahh. I missed that too.
Ok, leave the 64-bit field for now, while we think about this. But one option is to just use "atomic_andnot()" instead of clear_bit().
That would imply using an "atomic_t", which would be fairly natural (and would be 32-bit).
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.
Linus
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