From mboxrd@z Thu Jan 1 00:00:00 1970 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 D9BCA679E4; Tue, 30 Jan 2024 11:52:31 +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=1706615552; cv=none; b=twrCa2Woe02fqTrpcNeEAore2k6/mAWhbGp8bs/e0o7CqcKMKgQeFJdUM3SkeW5WpSArhUHYiAMPTYBQOQONN8Vx5CaQDefXxahoKksPo39hxexemYpYcOPanot8xZfNVH+H2Xx+ewVw9J319iCt67Mwad2424cdgDIXUIN9ZwI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706615552; c=relaxed/simple; bh=DMspNHe+PyuwZG/IydiW/Wdtvh3uR5JF2oe/i9uuk5Y=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Q6veGF+Xb+q5G1IsBvw+qQndDBnTwhcIcQSBAKBAZkKar9JeyAo+YWe9guO+dvxSLwEbWelE3UlBiC4ewSn6ec7B55ncQ8Da9JPZGNdgvWzsJvfGJXo8RHMUS89RhGHTGMxc4n9Qz5x62tBAVpwzPhLBdSMd+Sr6HROk5v8Rrk4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tLd3MiRr; 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="tLd3MiRr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BD77C433F1; Tue, 30 Jan 2024 11:52:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706615551; bh=DMspNHe+PyuwZG/IydiW/Wdtvh3uR5JF2oe/i9uuk5Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tLd3MiRrPCcMgjVjHBWZko6Az5rZSFR1TS04dBkF6SIlhgzavZ2stqYFKUjlYdcgz CUm7cZDSLxFrXzePWm05avfoOHKiqK3DWlv/ZpMl4Fbk24sTIvCe9Ad7MmJZ7Huvvi JK1VLQEXMckAltshWu+H0x/ncIpjIlmb5TTFb6OVzHS8xm9VPhnBxdPSJwFZ7kx29b O4hDrkrHy1F2o3o8FdBROYbPGiljw4vd+CDssP8WvjexD/SSs6VTTDk/bMsGGQ/WhM +yAfrdEE4Gke6UPP5de/5dsmvbanSxCQT9o+813w0EqxCvGItuM9kUDGYXnlZQog6a j5Pwxm/sKwtkg== Date: Tue, 30 Jan 2024 19:39:35 +0800 From: Jisheng Zhang To: Petr =?utf-8?B?VGVzYcWZw61r?= Cc: Alexandre Torgue , Jose Abreu , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Maxime Coquelin , Chen-Yu Tsai , Jernej Skrabec , Samuel Holland , "open list:STMMAC ETHERNET DRIVER" , "moderated list:ARM/STM32 ARCHITECTURE" , "moderated list:ARM/STM32 ARCHITECTURE" , open list , "open list:ARM/Allwinner sunXi SoC support" , Marc Haber , Andrew Lunn , Florian Fainelli , stable@vger.kernel.org Subject: Re: [PATCH net v2] net: stmmac: protect updates of 64-bit statistics counters Message-ID: References: <20240128193529.24677-1-petr@tesarici.cz> <20240130083539.4ea26a8d@meshulam.tesarici.cz> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240130083539.4ea26a8d@meshulam.tesarici.cz> On Tue, Jan 30, 2024 at 08:35:39AM +0100, Petr Tesařík wrote: > On Tue, 30 Jan 2024 13:00:10 +0800 > Jisheng Zhang wrote: > > > On Sun, Jan 28, 2024 at 08:35:29PM +0100, Petr Tesarik wrote: > > > As explained by a comment in , write side of struct > > > u64_stats_sync must ensure mutual exclusion, or one seqcount update could > > > be lost on 32-bit platforms, thus blocking readers forever. Such lockups > > > have been observed in real world after stmmac_xmit() on one CPU raced with > > > stmmac_napi_poll_tx() on another CPU. > > > > > > To fix the issue without introducing a new lock, split the statics into > > > three parts: > > > > > > 1. fields updated only under the tx queue lock, > > > 2. fields updated only during NAPI poll, > > > 3. fields updated only from interrupt context, > > > > > > Updates to fields in the first two groups are already serialized through > > > other locks. It is sufficient to split the existing struct u64_stats_sync > > > so that each group has its own. > > > > > > Note that tx_set_ic_bit is updated from both contexts. Split this counter > > > so that each context gets its own, and calculate their sum to get the total > > > value in stmmac_get_ethtool_stats(). > > > > > > For the third group, multiple interrupts may be processed by different CPUs > > > at the same time, but interrupts on the same CPU will not nest. Move fields > > > from this group to a newly created per-cpu struct stmmac_pcpu_stats. > > > > > > Fixes: 133466c3bbe1 ("net: stmmac: use per-queue 64 bit statistics where necessary") > > > Link: https://lore.kernel.org/netdev/Za173PhviYg-1qIn@torres.zugschlus.de/t/ > > > Cc: stable@vger.kernel.org > > > Signed-off-by: Petr Tesarik > > > > Thanks for the fix patch. One trivial improviement below > > s/netdev_alloc_pcpu_stats/devm_netdev_alloc_pcpu_stats to simplify > > error and exit code path. > > Thanks for your review. > > In fact, many other allocations in stmmac could be converted to devm_*. > I wanted to stay consistent with the existing code, but hey, you're there's already devm_* usage in stmmac_dvr_probe(), eg. devm_alloc_etherdev_mqs I believe other parts are from the old days when there's no devm_* APIs > right there's no good reason for it. > > Plus, I can send convert the other places with another patch. > > > With that: > > Reviewed-by: Jisheng Zhang > > > > PS: when I sent the above "net: stmmac: use per-queue 64 bit statistics > > where necessary", I had an impression: there are too much statistics in > > stmmac driver, I didn't see so many statistics in other eth drivers, is > > it possible to remove some useless or not that useful statistic members? > > I don't feel authorized to make the decision. But I also wonder about > some counters. For example, why is there tx_packets and tx_pkt_n? The > former is shown as RX packets by "ip stats show dev end0", the latter > is shown by as tx_pkt_n by "ethtools -S end0". The values do differ, > but I have no clue why, and if they are even expected to be different > or if it's a bug. > > Petr T