linux-kernel - [PATCH v2 1/5] time/sched_clock: Swap update_clock_read

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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

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@...gle.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