On Mon, 24 Apr 2017 08:43:18 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> On Mon, 24 Apr 2017 10:51:54 +0200 > Peter Zijlstra <pet...@infradead.org> wrote: > > > On Fri, Apr 21, 2017 at 10:49:29PM -0400, Steven Rostedt wrote: > > > When a CPU schedules in a lower priority task and wants to make sure > > > overloaded CPUs know about it. It increments the rto_loop_next. Then it > > > does > > > an atomic_inc_return() on rto_loop_start. If the returned value is not > > > "1", > > > then it does atomic_dec() on rt_loop_start and returns. If the value is > > > "1", > > > then it will take the rto_lock to synchronize with a possible IPI being > > > sent > > > around to the overloaded CPUs. > > > > > + start = atomic_inc_return(&rq->rd->rto_loop_start); > > > + if (start != 1) > > > + goto out; > > > > > +out: > > > + atomic_dec(&rq->rd->rto_loop_start); > > > > > > Did you just write a very expensive test-and-set trylock? > > Probably. I didn't know we had a generic one. Where is it? > > $ git grep test_and_set |grep trylock > fs/jfs/jfs_metapage.c:#define trylock_metapage(mp) > test_and_set_bit_lock(META_locked, &(mp)->flag) > > I don't think the above is what you mean. Or do you mean to just use test_and_set instead? -- Steve
