On Wed, Jun 07, 2017 at 03:17:27PM +0200, Peter Zijlstra wrote:
> > +static inline void arch_spin_unlock(arch_spinlock_t *lock)
> > +{
> > + __asm__ __volatile__ (
> > + "amoswap.w.rl x0, x0, %0"
> > + : "=A" (lock->lock)
> > + :: "memory");
> > +}
> > +
> > +static inline int arch_spin_trylock(arch_spinlock_t *lock)
> > +{
> > + int tmp = 1, busy;
> > +
> > + __asm__ __volatile__ (
> > + "amoswap.w.aq %0, %2, %1"
> > + : "=r" (busy), "+A" (lock->lock)
> > + : "r" (tmp)
> > + : "memory");
> > +
> > + return !busy;
> > +}
One other thing, you need to describe the acquire/release semantics for
your platform. Is the above lock RCpc or RCsc ? If RCpc, you need to
look into adding smp_mb__after_unlock_lock().
