Messages in this thread | | | Date | Wed, 8 Jul 2020 17:35:22 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v3 06/20] seqlock: Extend seqcount API with associated locks |
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On Wed, Jul 08, 2020 at 05:09:30PM +0200, Ahmed S. Darwish wrote: > On Wed, Jul 08, 2020 at 02:29:38PM +0200, Peter Zijlstra wrote:
> > How about something disguisting like this then? > > > ... > > #define __SEQ_RT IS_BUILTIN(CONFIG_PREEMPT_RT) > > > > SEQCOUNT_LOCKTYPE(raw_spinlock, raw_spinlock_t, false, lock) > > SEQCOUNT_LOCKTYPE(spinlock, spinlock_t, __SEQ_RT, lock) > > SEQCOUNT_LOCKTYPE(rwlock, rwlock_t, __SEQ_RT, lock) > > SEQCOUNT_LOCKTYPE(mutex, struct mutex, true, lock) > > SEQCOUNT_LOCKTYPE(ww_mutex, struct ww_mutex, true, lock->base) > > > > #if (defined(CONFIG_CC_IS_GCC) && CONFIG_GCC_VERSION < 40900) || defined(__CHECKER__) > > > > #define __seqprop_pick(const_expr, s, locktype, prop, otherwise) \ > > __builtin_choose_expr(const_expr, \ > > __seqprop_##locktype##_##prop((void *)(s)), \ > > otherwise) > > > > extern void __seqprop_invalid(void); > > > > #define __seqprop(s, prop) \ > > __seqprop_pick(__same_type(*(s), seqcount_t), (s), seqcount, prop, \ > > __seqprop_pick(__same_type(*(s), seqcount_raw_spinlock_t), (s), raw_spinlock, prop, \ > > __seqprop_pick(__same_type(*(s), seqcount_spinlock_t), (s), spinlock, prop, \ > > __seqprop_pick(__same_type(*(s), seqcount_rwlock_t), (s), rwlock, prop, \ > > __seqprop_pick(__same_type(*(s), seqcount_mutex_t), (s), mutex, prop, \ > > __seqprop_pick(__same_type(*(s), seqcount_ww_mutex_t), (s), ww_mutex, prop, \ > > __seqprop_invalid())))))) > > > > #else > > > > #define __seqprop_case(s, locktype, prop) \ > > seqcount_##locktype##_t: __seqprop_##locktype##_##prop((void *)s) > > > > #define __seqprop(s, prop) \ > > _Generic(*(s), \ > > seqcount_t: __seqprop_seqcount_##prop((void*)s),\ > > __seqprop_case((s), raw_spinlock, prop), \ > > __seqprop_case((s), spinlock, prop), \ > > __seqprop_case((s), rwlock, prop), \ > > __seqprop_case((s), mutex, prop), \ > > __seqprop_case((s), ww_mutex, prop)) > > > > #endif > > > > #define __to_seqcount_t(s) __seqprop(s, ptr) > > #define __associated_lock_is_preemptible(s) __seqprop(s, preempt) > > #define __assert_associated_lock_held(s) __seqprop(s, assert) > > Hmm, I'll prototype the whole thing (along with PREEMPT_RT associated > lock()/unlock() as you've mentioned in the other e-mail), and come back. > > Honestly, I have a first impression that this is heading into too much > complexity and compaction, but let's finish the whole thing first.
So the thing I pasted compiles kernel/sched/cputime.o, but that only uses the old seqcount_t thing, not any of the fancy new stuff, still the compiler groks it all.
And while the gcc-4.8 code is horrendous crap, the rest should be pretty straight forward and concentrates on the pieces where there are differences.
I even considered:
#define __SEQPROP(name, prop, expr) \ static __always_inline __seqprop_##prop##_t \ __seqprop##name##_##prop(seqcount##name##_t *s) \ { \ expr; \ }
Such that we could write:
__SEQPROP(, ptr, return s) __SEQPROP(, preempt, return false) __SEQPROP(, assert, )
__SEQPROP(_##locktype, ptr, return &s->seqcount) \ __SEQPROP(_##locktype, preempt, return preempt) \ __SEQPROP(_##locktype, assert, __SEQCOUNT_LOCKDEP(lockdep_assert_held(s->lockmember))) \
But I figured _that_ might've been one step too far ;-)
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