linux-kernel - [PATCH 2/5] seqlock: change __seqprop() to return the function pointer

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Message-ID: <20230913154956.GA26245@redhat.com>
Date:   Wed, 13 Sep 2023 17:49:56 +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 2/5] seqlock: change __seqprop() to return the function
 pointer

Preparation, see the next patch.

This way it is trivial to add the new seqprop's with 2 or more args,
and we do not loose the type info.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 include/linux/seqlock.h | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index ac6631bd5706..41e36f8afad4 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -200,9 +200,9 @@ typedef struct seqcount_##lockname {					\
 } seqcount_##lockname##_t;						\
 									\
 static __always_inline seqcount_t *					\
-__seqprop_##lockname##_ptr(seqcount_##lockname##_t *s)			\
+__seqprop_##lockname##_ptr(const seqcount_##lockname##_t *s)		\
 {									\
-	return &s->seqcount;						\
+	return (void *)&s->seqcount; /* drop const */			\
 }									\
 									\
 static __always_inline unsigned						\
@@ -292,19 +292,19 @@ SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     mutex)
 #define SEQCNT_WW_MUTEX_ZERO(name, lock) 	SEQCOUNT_LOCKNAME_ZERO(name, lock)
 
 #define __seqprop_case(s, lockname, prop)				\
-	seqcount_##lockname##_t: __seqprop_##lockname##_##prop((void *)(s))
+	seqcount_##lockname##_t: __seqprop_##lockname##_##prop
 
 #define __seqprop(s, prop) _Generic(*(s),				\
-	seqcount_t:		__seqprop_##prop((void *)(s)),		\
+	seqcount_t:		__seqprop_##prop,			\
 	__seqprop_case((s),	raw_spinlock,	prop),			\
 	__seqprop_case((s),	spinlock,	prop),			\
 	__seqprop_case((s),	rwlock,		prop),			\
 	__seqprop_case((s),	mutex,		prop))
 
-#define seqprop_ptr(s)			__seqprop(s, ptr)
-#define seqprop_sequence(s)		__seqprop(s, sequence)
-#define seqprop_preemptible(s)		__seqprop(s, preemptible)
-#define seqprop_assert(s)		__seqprop(s, assert)
+#define seqprop_ptr(s)			__seqprop(s, ptr)(s)
+#define seqprop_sequence(s)		__seqprop(s, sequence)(s)
+#define seqprop_preemptible(s)		__seqprop(s, preemptible)(s)
+#define seqprop_assert(s)		__seqprop(s, assert)(s)
 
 /**
  * __read_seqcount_begin() - begin a seqcount_t read section w/o barrier
-- 
2.25.1.362.g51ebf55