On Tue, Mar 15, 2016 at 09:30:49AM -0700, Linus Torvalds wrote: > On Tue, Mar 15, 2016 at 5:15 AM, Ingo Molnar <mi...@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);
Ah! Now I remember why I used unsigned long :-s > > 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). I can try that. And then we would end up with atomic_fetch_or() and maybe the scheduler could keep its ad-hoc version until thread_info types get unified (if that's possible). > > 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 :-)
