From: Bart Van Assche <bvanassche@acm.org>
Date: Sun, 21 Jun 2020 21:24:36 +0000 (-0700)
Subject: Optimize the seqlock implementation
X-Git-Tag: fio-3.21~28^2~1
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=5fa0c063c6fe405200ec97e8f3703446dd8d82bc

Optimize the seqlock implementation

Use atomic_load_acquire() and atomic_store_release() instead of barriers
where appropriate.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---

diff --git a/lib/seqlock.h b/lib/seqlock.h
index 762b6ec1..afa9fd31 100644
--- a/lib/seqlock.h
+++ b/lib/seqlock.h
@@ -18,13 +18,12 @@ static inline unsigned int read_seqlock_begin(struct seqlock *s)
 	unsigned int seq;
 
 	do {
-		seq = s->sequence;
+		seq = atomic_load_acquire(&s->sequence);
 		if (!(seq & 1))
 			break;
 		nop;
 	} while (1);
 
-	read_barrier();
 	return seq;
 }
 
@@ -36,14 +35,12 @@ static inline bool read_seqlock_retry(struct seqlock *s, unsigned int seq)
 
 static inline void write_seqlock_begin(struct seqlock *s)
 {
-	s->sequence++;
-	write_barrier();
+	s->sequence = atomic_load_acquire(&s->sequence) + 1;
 }
 
 static inline void write_seqlock_end(struct seqlock *s)
 {
-	write_barrier();
-	s->sequence++;
+	atomic_store_release(&s->sequence, s->sequence + 1);
 }
 
 #endif