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[130.117.225.111]) by mx.google.com with ESMTPS id ffacd0b85a97d-48e71baf60asi29159432f8f.154.2026.11.03.02.11.08 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Nov 2026 02:11:08 -0800 (PST) Received-SPF: pass (google.com: domain of khorenko@virtuozzo.com designates 130.117.225.111 as permitted sender) client-ip=130.117.225.111; Authentication-Results: mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=relay header.b=LY2DYO50; spf=pass (google.com: domain of khorenko@virtuozzo.com designates 130.117.225.111 as permitted sender) smtp.mailfrom=khorenko@virtuozzo.com; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=virtuozzo.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Message-Id:Date:From:Subject:Content-Type: MIME-Version; bh=ZF7qRkA4tNkuH+7DkbZKU/WKRqFVSIsK/qdfhvqHyw0=; b=LY2DYO50UkFi CQgtiHhPTy5IiK+YQmnWzRT/ibQqiQITK+se303M/iPuU5olJeUwLofN9rqihToguzI6eK3OBBFgF f6H70ihmkvciSnBDG4Rpdz2XllTX8tXN8of+QGQDQ9UmxxxkuwPHux0VIKQOpXJAWCUXTWJLVnqC+ Gg6NaHkoT99vSdj8EgSQVkdnHoFvsP3yNMY55GRxDIZukDbeAIBfgzykj41O6aRBIQ4iRyEHhimpS xsNqYh206+MwrHX4j593xiJWUNYi9fMivWuSN5VEHBnJqkhqwJNZF54FEM0+FVtYmDgwwOc0Chh/8 ItynDEvfoqkxVSqH8M09NA==; Received: from ch-demo-asa.virtuozzo.com ([130.117.225.8] helo=f0.sw.ru) by relay.virtuozzo.com with esmtp (Exim 4.96) (envelope-from ) id 1xOBQ1-00BKVK-1p; Tue, 03 Nov 2026 11:10:59 +0100 MIME-Version: 1.0 From: Konstantin Khorenko To: Andrey Zhadchenko In-Reply-To: <20261103080358.723186-4-andrey.zhadchenko@virtuozzo.com> References: <20261103080358.723186-1-andrey.zhadchenko@virtuozzo.com> <20261103080358.723186-4-andrey.zhadchenko@virtuozzo.com> Date: Tue, 03 Nov 2026 11:11:03 +0100 Message-Id: <179370066312.2382033.1838606125401038702.b4-review@b4> X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1533; i=khorenko@virtuozzo.com; h=from:subject:message-id; bh=hDKkZmI1aVFiEdBrb/ofQsNoOl7PNvUQFpWWu2KaCjU=; b=owEBbQKS/ZANAwAKAVGWCkf5YVwqAcsmYgBq6bM5YAlMLj0lepIiziMRRm8UhmC7wbGjuN2Pf L6GuGPDQ+yJAjMEAAEKAB0WIQRWD23IPcXT0GO9CCxRlgpH+WFcKgUCaumzOQAKCRBRlgpH+WFc KipyD/9LQhpuVFrSEChdm+JWbq5c80hF5UIPV0Y9u6vDphcyOxcaOcftmaAFB5pzJAic5iqNQIJ oprxstVk0mYftKC5kv1JeTRsj4m6cISoWETDlMrN9mgCV27MvX+pr71oe+nlQTT5HuLPvLdWJsx /31EKFoyZgXfgbeMgo+QWmudwrFv8ddqkZ+IlUe3zyvO7c5HzxquQuLS2luQY9ziARCD3lNzJqS 3aFq3PcDXrxEpVQsM4U5pM6ynuG05w38ecDKUkgjRtT2pzMc68o7PO0E/ZZceWDOLkYumSmTgki k1JYeb0wgQ0ock79FYAjseJkJwv66do1sk4iOJx59hKTt6ojRTSkM9trrRj9WY3IslO9d3/e06w DDFWtgiYSyLzA6vKLuBuIUcLS+YlmZKHUgXZl7Z2ZQgj8GT/4q8ufb9r4xC6ByW1Px3BHvEADvH 5rXQPrH8PX8rE0ZL1E1y7279DqvNriBSHiDvLjqe92iIC+Syp1zGW6VGtIxnGNu3nvZf1oaNG49 tOVXbQQY0+Ao1NKi182f5o9gtkm1xttLYHVy6Tw6lAp1k64Ex5Ku1ZXvhbfaxJIHSiYGVXeEhBq wmUgsh8DUnhZOO7UqfrBqPE1UQNgBpmbVUxC/wYWlpYBMzukwPU9oyJ6um0Mchy5dy0Qt+7dq1c UmdLm37u4nlq0PQ== X-Developer-Key: i=khorenko@virtuozzo.com; a=openpgp; fpr=560F6DC83DC5D3D063BD082C51960A47F9615C2A X-OZ-Fwd: true Cc: devel@openvz.org Subject: Re: [Devel] [PATCH hci-8.1 v4 3/6] drivers/md/push_backup: do not re-arm deadline timer in push_backup_write() X-BeenThere: devel@openvz.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: OpenVZ development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: devel-bounces@openvz.org Errors-To: devel-bounces@openvz.org On 11/3/26 11:03, Andrey Zhadchenko wrote: > pb_timer_func() checks pb->deadline_jiffies every time it fires, > so we actually don't need to re-arm the timer after setting the > field. Hi Andrey, That holds only while the timer is pending whenever writes are delayed, and at this point of the series it is not always so. Both arming sites still decide under pb->lock and call mod_timer() after dropping it: CPU1 pb_timer_func() CPU2 postpone_if_required_for_backup() lock; deadline = S64_MAX unlock lock; nr_delayed = 1 deadline_jiffies = now + timeout unlock mod_timer(timeout) mod_timer(from S64_MAX) The write is delayed with the timer parked for days. Before this patch the next push_backup_write() that left requests delayed re-armed the timer and repaired it. After it nothing does until nr_delayed drops to zero or stop. 5/6 closes the race, so please put 5/6 before this patch or fold the two, so that no bisect point carries the window. > This is also the only place that arms the timer outside the window > push_backup_stop() waits for with synchronize_rcu(). pb_timer_func() re-arms the timer outside that window too: a firing that starts after synchronize_rcu() runs concurrently with timer_delete_sync_try(). Please drop "the only place" here and in the cover letter. -- Konstantin Khorenko, Virtuozzo Linux Kernel Team _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel