linux-kernel - [PATCH 1/5] seqlock: simplify SEQCOUNT

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Message-ID: <20230913154953.GA26242@redhat.com>
Date:   Wed, 13 Sep 2023 17:49:53 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Boqun Feng <boqun.feng@...il.com>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...riel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Waiman Long <longman@...hat.com>, Will Deacon <will@...nel.org>
Cc:     Alexey Gladkov <legion@...nel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/5] seqlock: simplify SEQCOUNT_LOCKNAME()

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.

Signed-off-by: Oleg Nesterov <oleg@...hat.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