From: Paul E. McKenney <paulmck@kernel.org>
Date: Tue, 1 Aug 2023 16:30:18 +0000 (-0700)
Subject: refscale: Fix misplaced data re-read
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=730c3ed4ba30feadfb20b4d4d18e869bc00348f6;p=users%2Fjedix%2Flinux-maple.git

refscale: Fix misplaced data re-read

This commit fixes a misplaced data re-read in the typesafe code.
The reason that this was not noticed is that this is a performance test
with no writers, so a mismatch could not occur.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 91a0fd0d4d9ab..750a63e995390 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -655,12 +655,12 @@ retry:
 			goto retry;
 		}
 		un_delay(udl, ndl);
+		b = READ_ONCE(rtsp->a);
 		// Remember, seqlock read-side release can fail.
 		if (!rts_release(rtsp, start)) {
 			rcu_read_unlock();
 			goto retry;
 		}
-		b = READ_ONCE(rtsp->a);
 		WARN_ONCE(a != b, "Re-read of ->a changed from %u to %u.\n", a, b);
 		b = rtsp->b;
 		rcu_read_unlock();