From nobody Thu Sep 24 16:57:26 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AF385352014 for ; Tue, 22 Sep 2026 01:22:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790040175; cv=none; b=QGl0BJo3GeSuMYxOF0KzRemmTISxofJOU01G++7IWvEA1Ac1nKtw45mVTuW0YztQDnxDv+2xtfbbvc4RyiSg43l0LE7fY7+8iTMVNI1LoAP0i6SIwQcaBH+Qmu5it0DRfXHAlxSK74UGFH1gpRB/AkSzDWlQa5VbkuICLqVLexw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790040175; c=relaxed/simple; bh=K+FfnXxqpOwARf6sBlGuwolcSmz6gqc31RO65RLjJX0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=Cr1kWMgX0kox5Dvm/4Jb7N1heGearbK100oAS2H1tuVY3NU7V5XNgLyL4Pj5W30D0DI7XtOMS8za/xXMQ6Nos++AsVaNNehlCZxF3Q7qLLceWx4xa0Tswg9ZAkJcIczJdgyM6kmHeTwDupYqqvorW94lNiWb8fCvQ17vf+oLt7s= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Xwf0Tz/x; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Xwf0Tz/x" Received: by smtp.kernel.org (Postfix) with ESMTPS id 36A4FC2BCB3; Tue, 22 Sep 2026 01:22:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1790040175; bh=K+FfnXxqpOwARf6sBlGuwolcSmz6gqc31RO65RLjJX0=; h=From:Date:Subject:To:Cc:Reply-To:From; b=Xwf0Tz/xlKPpp2CEUAgMk+UDu2RpOrYhT5PSFsyXO2O6Al+O64T1llvGr8qr+/Lfm UFmI92ORneTpwyiYywPQGTJiuepPtYo3yQfF/c/OsD91w/XHjgaGMlK7qEBx+rCHiT QPUdMOorZe6KD7PqUyDrb5iTPAxy6Gyk18plk2j5wmd4pkg7L/lu2D5bhgDcNjxh6T jp32i+M+9AV7t3VoixTpe+gY3Rq2AdA8h+nJ0K70jSmu8BUU6QuP9Vt5yNMvcWbT2n ZYKUv10B6bWXTSSvDGeRIJ23XsIYQ0d8MN7dQkevkFCfUHWDfbSP92HgdsW/K8tLtC noI+nLrnVJB1A== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22817C982FC; Tue, 22 Sep 2026 01:22:55 +0000 (UTC) From: Jaidev Shastri via B4 Relay Date: Mon, 21 Sep 2026 21:22:53 -0400 Subject: [PATCH] clocksource: publish finished_booting with release semantics Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260921-mb-clocksource-v1-1-3e1d1b43e90d@vt.edu> X-B4-Tracking: v=1; b=H4sIAGzYsWoC/yXMzQ7CIBAE4Fdp9uwaiqSKr2I8wHa1+APNYhuTp u8u1OM3mZkFMkvgDOdmAeE55JBiQbtrgAYX74yhLwatdKesbvHtkV6JnjlNQozGUq+8Np07WSi jUfgWvtvh5fp3nvyD6VNfasO7zOjFRRpqtHE+7g8oZGBdfwVdrTySAAAA X-Change-ID: 20260921-mb-clocksource-49cd0b246a89 To: John Stultz , Thomas Gleixner , Stephen Boyd , Miroslav Lichvar Cc: linux-kernel@vger.kernel.org, Jaidev Shastri X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1790040174; l=1624; i=jaidevshastri@vt.edu; s=20260921; h=from:subject:message-id; bh=IAl0WbtKNjLjhpFUlA0q6EePMhVi1mc72PuB7KQ2WK4=; b=KNo/OoqiMXNeaiOdEXN5kppi9PH+zt3BA68jLeg85EjayHobskzow7978IsWzKW4M/OG66uA/ dfpQkzE9RJPAhPNLn1W4tHEr9Kyw1O7JQ7vV8VVKg4NECG+kHf/i6+m X-Developer-Key: i=jaidevshastri@vt.edu; a=ed25519; pk=J7+xYJRlTPds+pv5hbqFFRqGCpDeJDzmZT1ggRwj7/0= X-Endpoint-Received: by B4 Relay for jaidevshastri@vt.edu/20260921 with auth_id=1044 X-Original-From: Jaidev Shastri Reply-To: jaidevshastri@vt.edu From: Jaidev Shastri clocksource_done_booting() sets curr_clocksource and then finished_booting, both with plain stores under clocksource_mutex. clocksource_find_best() tests finished_booting with a plain load before it walks clocksource_list. Set the flag with smp_store_release() and read it with smp_load_acquire(). Found with MBCheck, a static herd7-based memory consistency checker. Signed-off-by: Jaidev Shastri --- kernel/time/clocksource.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index f1253f579..f683a787c 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -1086,7 +1086,8 @@ static struct clocksource *clocksource_find_best(bool= oneshot, bool skipcur) { struct clocksource *cs; =20 - if (!finished_booting || list_empty(&clocksource_list)) + /* Pairs with the smp_store_release() in clocksource_done_booting(). */ + if (!smp_load_acquire(&finished_booting) || list_empty(&clocksource_list)) return NULL; =20 /* @@ -1188,7 +1189,8 @@ static int __init clocksource_done_booting(void) { mutex_lock(&clocksource_mutex); curr_clocksource =3D clocksource_default_clock(); - finished_booting =3D 1; + /* Pairs with the smp_load_acquire() in clocksource_find_best(). */ + smp_store_release(&finished_booting, 1); /* * Run the watchdog first to eliminate unstable clock sources */ --- base-commit: 93f51579e7df248780214094418f205253383cc5 change-id: 20260921-mb-clocksource-49cd0b246a89 Best regards, -- =20 Jaidev Shastri