From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) (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 373892D838E; Mon, 31 Aug 2026 07:30:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788161444; cv=none; b=Ogr8409qoEEyXhCC3Op5zA0zsA4/lFsgnOkeR5q7UeOjqq9x4N8Axt/3iIdOOXu1TY9wyF8bkDfEEtJTOeviryPnn8gbbYn3NTSifr7WmZmzlSswfllwdCOkqPe+baAixGtR8uxWwJeymzGV0fH1YFyH3C+SpugEFIVXI/hEa8s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788161444; c=relaxed/simple; bh=Q+IuMSlpQzt2kZCTJZXgjd64tnopR9oFjZyuOJCKVNg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IFcOalGUtpoZko/bgwYqV/FrWE4hcKjg60Tey6HIqpzKL2WGxssM4pNy6Or2GF2rxHuPm0pPjnqKrjPHJ06LTwvP9VyH7XHEhgum1hRPXlVg2312CV8qlFA7UqN9eAtUMW5hkaeE3p3Z1/Cndt/CeP8lE7nJXYi1WPzE9wZP9bo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=j0Jau098; arc=none smtp.client-ip=192.198.163.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="j0Jau098" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1788161443; x=1819697443; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Q+IuMSlpQzt2kZCTJZXgjd64tnopR9oFjZyuOJCKVNg=; b=j0Jau098bY0IwqmGO22bnJJTMGzyxVBY/fClfJLm9Fd9pSNJ72f0yROA 6Bpk6QAAY3vYb1bi86tSiCLtcbXfUlLiaZExyTdbJZ01ysm1s3Ga4zwQE PNHFc571zAb58rD2KfcwJ85my8jYAHJh0oKks4CMzshf6HTeP0Q60t1pO cD2llaVWPFq8pNx8JO6xNmki5xDn73HkktFKv+S0vz3Ugq4TzgTo6JfdO h+0pAwGYbq7T6DB4HMb/ZaykCfPFuMYLElxVZAVxSLitW1u5XUKta/nLn I3ojcI3bJmTUkyMEHUKBaVFGoZPQgMU0/ZZvqP7gYZ4yAvU9qLDa+nziF A==; X-CSE-ConnectionGUID: VtN56IAGS0GyB9381yR3Sw== X-CSE-MsgGUID: +5bSnh3ARWuwjBqeKqz1eQ== X-IronPort-AV: E=McAfee;i="6800,10657,11891"; a="99160569" X-IronPort-AV: E=Sophos;i="6.25,252,1779174000"; d="scan'208";a="99160569" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Aug 2026 00:30:42 -0700 X-CSE-ConnectionGUID: CuvcaCpmS0uo8MoLP33PQQ== X-CSE-MsgGUID: sVvopwRsQTW9Nzt0o+Uqog== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,252,1779174000"; d="scan'208";a="272514915" Received: from junjie-desk-dev.bj.intel.com (HELO junjie-desk-dev.tail2c02c1.ts.net) ([10.238.152.71]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Aug 2026 00:30:39 -0700 From: Junjie Cao To: Jakub Kicinski Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, horms@kernel.org, jhs@mojatatu.com, jiri@resnulli.us, vinicius.gomes@intel.com, shuah@kernel.org, bestswngs@gmail.com, uladzislau.zhauniarovich@gmail.com, hdanton@sina.com, syzbot+19d01f6082ec61dd45b2@syzkaller.appspotmail.com, syzbot+8785aaf121cfb2141e0d@syzkaller.appspotmail.com, syzbot+2642f347f7309b4880dc@syzkaller.appspotmail.com, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH net v2 1/3] net/sched: taprio: catch up in bounded time when the schedule falls behind Date: Mon, 31 Aug 2026 15:30:25 +0800 Message-ID: <20260831073025.409831-1-junjie.cao@intel.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260824185335.2703968-1-kuba@kernel.org> References: <20260824185335.2703968-1-kuba@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Mon, 24 Aug 2026 11:53:35 -0700, Jakub Kicinski wrote: > No Link: tags present in the commit header. v3 will carry the syzbot tags, including a fourth bucket akpm had syzbot test this patch alone against: https://lore.kernel.org/all/6a936ec2.4d659fcc.734b4.0032.GAE@google.com/ > has a second exit condition (--budget), so taprio_catch_up() can return [...] > jump makes end == now, and the strict ktime_before(end, now) test then skips Right. v3 treats end == now as behind, in the walk and its caller, and the comment mentions the cap. > case, so a large gate control list turns a previously O(1) critical section > into an O(num_entries) walk over separately allocated entries. One lap at most per hold now, versus no bound at all before. Leaving it as is. > inoperative. Adding N * cycle_time then shifts the timeline by > (N * cycle_time) modulo the interval sum, and the gate_close_time[] values Yes. v3 jumps whole laps instead: min(cycle_time, sum of intervals) on the entry timeline, cycle_time on cycle_end_time, i.e. exactly what N restarts of the current code do. > then terminates on budget exhaustion with end < now, and behind stays below [...] > changelog describes does not converge at all. Is the intent that this patch > depends on the minimum interval patch for the bound to hold? No. With the jump in laps the residual is under one lap, so the walk finishes within num_entries steps for any schedule. v3 drops 2/3 anyway. > be observed torn, which is also pre-existing. Is it worth a comment that > advance_sched() may legitimately update the currently published entry? Yes, will add.