Re: [PATCH 1/5] seqlock: simplify SEQCOUNT_LOCKNAME()

Peter Zijlstra
2023-09-16T08:54:52Z

On Wed, Sep 13, 2023 at 05:49:53PM +0200, Oleg Nesterov wrote:
> 1. Kill the "lockmember" argument. It is always s->lock plus
> __seqprop_##lockname##_sequence() already uses s->lock and
> ignores "lockmember".
>
> 2. Kill the "lock_acquire" argument. __seqprop_##lockname##_sequence()
> can use the same "lockbase" prefix for _lock and _unlock.
>
> Apart from line numbers, gcc -E outputs the same code.

With seqlock_ww_mutex gone, yes this is a nice cleanup.

>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
> include/linux/seqlock.h | 18 ++++++++----------
> 1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
> index 987a59d977c5..ac6631bd5706 100644
> --- a/include/linux/seqlock.h
> +++ b/include/linux/seqlock.h
> @@ -191,11 +191,9 @@ static inline void seqcount_lockdep_reader_access(const seqcount_t *s)
> * @lockname: "LOCKNAME" part of seqcount_LOCKNAME_t
> * @locktype: LOCKNAME canonical C data type
> * @preemptible: preemptibility of above locktype
> - * @lockmember: argument for lockdep_assert_held()
> - * @lockbase: associated lock release function (prefix only)
> - * @lock_acquire: associated lock acquisition function (full call)
> + * @lockbase: prefix for associated lock/unlock
> */
> -#define SEQCOUNT_LOCKNAME(lockname, locktype, preemptible, lockmember, lockbase, lock_acquire) \
> +#define SEQCOUNT_LOCKNAME(lockname, locktype, preemptible, lockbase) \
> typedef struct seqcount_##lockname { \
> seqcount_t seqcount; \
> __SEQ_LOCK(locktype *lock); \
> @@ -216,7 +214,7 @@ __seqprop_##lockname##_sequence(const seqcount_##lockname##_t *s) \
> return seq; \
> \
> if (preemptible && unlikely(seq & 1)) { \
> - __SEQ_LOCK(lock_acquire); \
> + __SEQ_LOCK(lockbase##_lock(s->lock)); \
> __SEQ_LOCK(lockbase##_unlock(s->lock)); \
> \
> /* \
> @@ -242,7 +240,7 @@ __seqprop_##lockname##_preemptible(const seqcount_##lockname##_t *s) \
> static __always_inline void \
> __seqprop_##lockname##_assert(const seqcount_##lockname##_t *s) \
> { \
> - __SEQ_LOCK(lockdep_assert_held(lockmember)); \
> + __SEQ_LOCK(lockdep_assert_held(s->lock)); \
> }
>
> /*
> @@ -271,10 +269,10 @@ static inline void __seqprop_assert(const seqcount_t *s)
>
> #define __SEQ_RT IS_ENABLED(CONFIG_PREEMPT_RT)
>
> -SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t, false, s->lock, raw_spin, raw_spin_lock(s->lock))
> -SEQCOUNT_LOCKNAME(spinlock, spinlock_t, __SEQ_RT, s->lock, spin, spin_lock(s->lock))
> -SEQCOUNT_LOCKNAME(rwlock, rwlock_t, __SEQ_RT, s->lock, read, read_lock(s->lock))
> -SEQCOUNT_LOCKNAME(mutex, struct mutex, true, s->lock, mutex, mutex_lock(s->lock))
> +SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t, false, raw_spin)
> +SEQCOUNT_LOCKNAME(spinlock, spinlock_t, __SEQ_RT, spin)
> +SEQCOUNT_LOCKNAME(rwlock, rwlock_t, __SEQ_RT, read)
> +SEQCOUNT_LOCKNAME(mutex, struct mutex, true, mutex)
>
> /*
> * SEQCNT_LOCKNAME_ZERO - static initializer for seqcount_LOCKNAME_t
> --
> 2.25.1.362.g51ebf55
>