On Fri, Aug 28, 2020 at 03:07:09AM +0200, Ahmed S. Darwish wrote: > +/* > + * Automatically disable preemption for seqcount_LOCKTYPE_t writers, if the > + * associated lock does not implicitly disable preemption. > + * > + * Don't do it for PREEMPT_RT. Check __SEQ_LOCK(). > + */ > +#define __seq_enforce_preemption_protection(s) > \ > + (!IS_ENABLED(CONFIG_PREEMPT_RT) && __seqcount_lock_preemptible(s))
Hurph, so basically you want to make __seqcount_lock_preemptible() return true PREEMPT_RT ? Should we then not muck about with the propery instead of this? ISTR I had something like the below, would that not be the same but much clearer ? diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index 300cbf312546..3b5ad026ddfb 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -211,11 +211,13 @@ static inline void __seqcount_assert(seqcount_t *s) lockdep_assert_preemption_disabled(); } -SEQCOUNT_LOCKTYPE(raw_spinlock_t, raw_spinlock, false, s->lock) -SEQCOUNT_LOCKTYPE(spinlock_t, spinlock, false, s->lock) -SEQCOUNT_LOCKTYPE(rwlock_t, rwlock, false, s->lock) -SEQCOUNT_LOCKTYPE(struct mutex, mutex, true, s->lock) -SEQCOUNT_LOCKTYPE(struct ww_mutex, ww_mutex, true, &s->lock->base) +#define __PREEMPT_RT IS_BUILTIN(CONFIG_PREEMPT_RT) + +SEQCOUNT_LOCKTYPE(raw_spinlock_t, raw_spinlock, false, s->lock) +SEQCOUNT_LOCKTYPE(spinlock_t, spinlock, __PREEMPT_RT, s->lock) +SEQCOUNT_LOCKTYPE(rwlock_t, rwlock, __PREEMPT_RT, s->lock) +SEQCOUNT_LOCKTYPE(struct mutex, mutex, true, s->lock) +SEQCOUNT_LOCKTYPE(struct ww_mutex, ww_mutex, true, &s->lock->base) /* * SEQCNT_LOCKNAME_ZERO - static initializer for seqcount_LOCKNAME_t