On Tue, Jun 26, 2018 at 09:53:18PM +0300, Andy Shevchenko wrote: > On Mon, Jun 25, 2018 at 1:59 PM, Mark Rutland <[email protected]> wrote: > > From: Peter Zijlstra <[email protected]> > > > > Mark found ldsem_cmpxchg() needed an (atomic_long_t *) cast to keep > > working after making the atomic_long interface type safe. > > > > Needing casts is bad form, which made me look at the code. There are no > > ld_semaphore::count users outside of these functions so there is no > > reason why it can not be an atomic_long_t in the first place, obviating > > the need for this cast. > > > > That also ensures the loads use atomic_long_read(), which implies (at > > least) READ_ONCE() in order to guarantee single-copy-atomic loads. > > > > When using atomic_long_try_cmpxchg() the ldsem_cmpxchg() wrapper gets > > very thin (the only difference is not changing *old on success, which > > most callers don't seem to care about). > > > > So rework the whole thing to use atomic_long_t and its accessors > > directly. > > > > While there, fixup all the horrible comment styles. > > > > - ldsem_atomic_update(-LDSEM_WAIT_BIAS, sem); > > + atomic_long_add_return(-LDSEM_WAIT_BIAS, &sem->count); > > I suppose it's simple atomic_long_add() here?
Different ordering rules for those two. I didn't look hard enough to see if that mattered here.
