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 D7E354FDA6C for ; Tue, 22 Sep 2026 07:11:09 +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=1790061071; cv=none; b=r48k0tImkkoosyWFWoVmbfJCaZSRVij5DuxL57/qRqfflUgrB1Ypzr+cUfwdj+Pf/FprFU7tptCS0bbSBs9FUmoxBISWVv/ny3Z3JKnHVf2FxAjnzDl0JmLSOMssQMD0p6PHE9FLRXA/OGdu0BMGMjKHfWd2HXeiH2JhyiLp7Gs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790061071; c=relaxed/simple; bh=0xo2mS5jsKLYw/NiCNhadaRGN+V6z/N9ydkcU8qg050=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gX4VagKINyK7dbjKg1QxyjNuBk+h5lyDkp4rSpwlwG1pHuuHMXpj8/iWogGG0LlD1LtjWJm/BpLt2lyd+KjaGrz1cM8tgXRgNk2g4JKHm0m1HDk8AsF2Ms979DjQTvJjWwRynYiQYiVGJdaCs6vFLpU4smPBNVwui1PIzAzhSkg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kuecoGXG; 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="kuecoGXG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E8C721F000FF; Tue, 22 Sep 2026 07:11:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790061069; bh=PbNtgUQWwIoKFqeaXdo7z9rWu5YQjPSpcUGQ4Swb8aw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=kuecoGXGO3X0s5sPAJqlIUweWzHw2mrBABmgFYaJn4nY5/i7OpcaPQFSnjtimJAYt nVyoV0N3n0vBxHj5+gi7Tz864gi1K0s999LV7jkIyMs0O14s519HzgczlC73yagt4w JRDIvCW3/O0Q8hmF3ytA0BO1LeFY70oxLnN+93SbFG0PDfaI1HpV/r8RkXnCcXPJzB mCV3HWOsx6oaj2xgPLD8y2ROQq0BEPlKVhAIR+T5bYkYpwcnGt/qiEI3S0bM9atuX/ efiE76GLkQLzDuF3Mlp8eBZXXFcKKj07tznRsgcoYx+oHhNt3DTQOgHb7sVrU4m/kV OI721Fy3SXF9A== Message-ID: <61c5c84e-30ce-4f2d-92d8-3d15fb1e1952@kernel.org> Date: Tue, 22 Sep 2026 09:11:05 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH net-next v2] net: opt loopback into instance locking Content-Language: fr To: Jakub Kicinski , davem@davemloft.net Cc: netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org References: <20260921190452.1467853-1-kuba@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Jakub, On 21/09/2026 21:04, Jakub Kicinski wrote: > netdev netlink iterates over devices when dumping queues/NAPIs/qstats > etc. and takes rtnl_lock or instance lock depending on the underlying > device. Currently even if all the "real" devices in the system are ops > locked we still have to take rtnl_lock for lo (only to find out > that it doesn't even have queues or NAPIs to report). > Opt loopback into having control path under the ops lock. > > This is a pretty obvious thing to do, I've held back this > patch because we used to only apply ops locking on physical devices. > netkit queue leasing made a precedent for (far more complex) > SW devices enabling ops locking. Now adding it to lo should > not create much new bug surface. > > I considered an alternative of adding a "predicate" to the iteration > primitive so that we can skip the devices which obviously don't > support given API (eg qstat) without any locking. But it's more > LoC and real_num_.x_queues is not currently WRITE_ONCE()ed so > it doesn't work too well for queues. Thank you for this! But apparently, it looks like it is still causing some issues with the BPF selftests for some arch, e.g. https://github.com/kernel-patches/bpf/actions/runs/35693264483/job/106636983010 Cheers, Matt --- (I don't know if I have the rights to ask for ↓) pw-bot: cr