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From: Marco Elver <elver@google.com>
To: elver@google.com, Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,  Will Deacon <will@kernel.org>,
	Waiman Long <longman@redhat.com>,
	Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	 Mark Rutland <mark.rutland@arm.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	kasan-dev@googlegroups.com,  linux-kernel@vger.kernel.org
Subject: [PATCH v2 1/5] time/sched_clock: Swap update_clock_read_data() latch writes
Date: Mon,  4 Nov 2024 16:43:05 +0100	[thread overview]
Message-ID: <20241104161910.780003-2-elver@google.com> (raw)
In-Reply-To: <20241104161910.780003-1-elver@google.com>

Swap the writes to the odd and even copies to make the writer critical
section look like all other seqcount_latch writers.

Signed-off-by: Marco Elver <elver@google.com>
---
v2:
* New patch.
---
 kernel/time/sched_clock.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
index 68d6c1190ac7..85595fcf6aa2 100644
--- a/kernel/time/sched_clock.c
+++ b/kernel/time/sched_clock.c
@@ -119,9 +119,6 @@ unsigned long long notrace sched_clock(void)
  */
 static void update_clock_read_data(struct clock_read_data *rd)
 {
-	/* update the backup (odd) copy with the new data */
-	cd.read_data[1] = *rd;
-
 	/* steer readers towards the odd copy */
 	raw_write_seqcount_latch(&cd.seq);
 
@@ -130,6 +127,9 @@ static void update_clock_read_data(struct clock_read_data *rd)
 
 	/* switch readers back to the even copy */
 	raw_write_seqcount_latch(&cd.seq);
+
+	/* update the backup (odd) copy with the new data */
+	cd.read_data[1] = *rd;
 }
 
 /*
-- 
2.47.0.163.g1226f6d8fa-goog


  reply	other threads:[~2024-11-04 16:19 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-11-04 15:43 [PATCH v2 0/5] kcsan, seqlock: Support seqcount_latch_t Marco Elver
2024-11-04 15:43 ` Marco Elver [this message]
2024-11-06 10:47   ` [tip: locking/core] time/sched_clock: Swap update_clock_read_data() latch writes tip-bot2 for Marco Elver
2024-11-04 15:43 ` [PATCH v2 2/5] time/sched_clock: Broaden sched_clock()'s instrumentation coverage Marco Elver
2024-11-05  9:22   ` Marco Elver
2024-11-05  9:35     ` Peter Zijlstra
2024-11-06 10:47   ` [tip: locking/core] " tip-bot2 for Marco Elver
2024-11-04 15:43 ` [PATCH v2 3/5] kcsan, seqlock: Support seqcount_latch_t Marco Elver
2024-11-06 10:47   ` [tip: locking/core] " tip-bot2 for Marco Elver
2024-11-04 15:43 ` [PATCH v2 4/5] seqlock, treewide: Switch to non-raw seqcount_latch interface Marco Elver
2024-11-06 10:47   ` [tip: locking/core] " tip-bot2 for Marco Elver
2024-11-04 15:43 ` [PATCH v2 5/5] kcsan, seqlock: Fix incorrect assumption in read_seqbegin() Marco Elver
2024-11-05  9:13   ` Peter Zijlstra
2024-11-05  9:28     ` Marco Elver
2024-11-05  9:34   ` Peter Zijlstra
2024-11-05  9:41     ` Peter Zijlstra
2024-11-05  9:50     ` Marco Elver
2024-11-06 10:47   ` [tip: locking/core] " tip-bot2 for Marco Elver

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