From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 DFA5B38AC78; Thu, 27 Aug 2026 04:29:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787804971; cv=none; b=btwkJ8mYDVqU73gpWQw+GVHfXhMECsHXdeB5isi2wc+06+PMDTp49GMx5TvZxlCMPRrLRiOi4zw6mjzlxWD7M9lPwsyGZMX7EMJ57exbXQNelWNCJUbQyCQ+8xgcMZqYX0SptU9GC5LE91qQBNUNqXGuxacDRmOqh7HwgH/GcBY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787804971; c=relaxed/simple; bh=Iv5b61T2zG01D+beUShN6F2FTZvVX8oN+yVJrw+ujzE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OK8kZmBMMK8QmaSloM8GOMjjHdpVa1kCKVAngXdEMBgPtDE5txRD1NWKBDYe4/Z402hyiqwGJs1lDU9AC7pcf9J3s5F1yTcpXdwH4VrUBxZiqTQiNa/aF3JdjqmE0r1gb41+LujB0jDiLZkkzB5lTqRSX4m+fY3sujYZHnHOlg4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=izYrMHPw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="izYrMHPw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FF341F00A3E; Thu, 27 Aug 2026 04:29:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787804969; bh=nERbAFEHHSw5ax7MRWud0rpkMohS2ci96UJ8OD+KyJc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=izYrMHPwxZ/T5mohTVMD2kb/EMqa5Sw1xgHZkTwTlhGJXkBmsvABfHygDlg84j6ry RueknLBCEZsnFp53JM/LEDbEMLrOb6zFh2FHV64Qer50CtGPcbnjnPAzGRuqKBPBu4 0fij/rL9wBRUJOzRG5fDySXAvMbil4F1h/J1oo5taORYj0Vqb2OrZY1Axz5UiKcCMK 0dLPK/8O3Xia6oTGIISTWtU7e7aXGERZuNtsa9AzZwtciEBXNy6Ntb+fA0g7cjR1OO 3svM2t9PAz+hdYacgQaho2YIQT1+SRnsdveN2DRY5Rk8nGMcXdTbOP45kA+Ow0VsOd EMBggIeJ1YlwQ== From: SJ Park To: Cc: SJ Park , stable@vger.kernel.org, Andrew Morton , Quanmin Yan , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 2/2] mm/damon/sysfs: set next refresh jiffies per sysfs context Date: Wed, 26 Aug 2026 21:29:19 -0700 Message-ID: <20260827042920.93580-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260827042920.93580-1-sj@kernel.org> References: <20260827042920.93580-1-sj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When 'refresh_ms' is set, DAMON sysfs interface periodically updates auto-tuned parameters and DAMOS stats. The timestamp for the next refresh is initialized when a DAMON context starts, and updated in its damon_call() callback function. That is, each DAMON context updates it. However, the timestamp is a global variable that is shared with all the contexts. When there are multiple DAMON contexts having different refresh_ms, the update frequency will be changed, depending on the order of the contexts. When there are multiple kdamonds, it will be even more chaotic. Fix the problem by having the timestamp per each context. The user impact is not very critical. It does not leak, corrupt or crash. The update will not be faster or slower than the lowest and largest refresh_ms values of the contexts, respectively. The user can also manually ask the updates on demand using kdamond state commands. That said, clearly this is a bug. Fixes: 9fd7bb5083d1 ("mm/damon/sysfs: change next_update_jiffies to a global variable") Cc: # 6.18.x Signed-off-by: SJ Park --- mm/damon/sysfs.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c index e3858ffab4b22..f05b256c90ee7 100644 --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -1789,6 +1789,7 @@ struct damon_sysfs_kdamond { struct damon_sysfs_contexts *contexts; struct damon_ctx *damon_ctx; unsigned int refresh_ms; + unsigned long next_refresh_jiffies; }; static struct damon_sysfs_kdamond *damon_sysfs_kdamond_alloc(void) @@ -2215,17 +2216,15 @@ static struct damon_ctx *damon_sysfs_build_ctx( return ctx; } -static unsigned long damon_sysfs_next_update_jiffies; - static int damon_sysfs_repeat_call_fn(void *data) { struct damon_sysfs_kdamond *sysfs_kdamond = data; if (!sysfs_kdamond->refresh_ms) return 0; - if (time_before(jiffies, damon_sysfs_next_update_jiffies)) + if (time_before(jiffies, sysfs_kdamond->next_refresh_jiffies)) return 0; - damon_sysfs_next_update_jiffies = jiffies + + sysfs_kdamond->next_refresh_jiffies = jiffies + msecs_to_jiffies(sysfs_kdamond->refresh_ms); if (!mutex_trylock(&damon_sysfs_lock)) @@ -2273,8 +2272,8 @@ static int damon_sysfs_turn_damon_on(struct damon_sysfs_kdamond *kdamond) } kdamond->damon_ctx = ctx; - damon_sysfs_next_update_jiffies = - jiffies + msecs_to_jiffies(kdamond->refresh_ms); + kdamond->next_refresh_jiffies = jiffies + + msecs_to_jiffies(kdamond->refresh_ms); repeat_call_control->fn = damon_sysfs_repeat_call_fn; repeat_call_control->data = kdamond; -- 2.47.3