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 A7BCF358D3D; Wed, 6 May 2026 22:35:03 +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=1778106903; cv=none; b=FDuyfPQHE6TzhVNSbPoi3JCTGrH4vCYfmB4lHPq3kxdhTu0cWeLQupLdYFWWq/r+3B6geNCvWVQdLmV87bh2nsypd8YRIqjRjcrCobsxuaVIEibFGI7J3wPd1SIATMwZO1okUG5XLVqd5ybeRA2iQZ2tK7Fj/7hCQVG8HNS7eGQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778106903; c=relaxed/simple; bh=WfZgw+TSYwuuWZco9UUiaSzl0XhRcbOTgHLl0PrSIY0=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=hDExhdrJvRtOSe7+QhDEFikqcjZH6HF4yyif03KFK1vCly3JWqgaKzjFl05Y8arpA0ATjpMn8MzEjghDdyURyDGOyYW57GbaZyy1WNzHiae4R9gjE0qh5jhJ/1W14LTypPrO9Or83GRxxI1RngBnqvRBHXVOHR/xPxFzuyzaG0E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CpdjeXb6; 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="CpdjeXb6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2606AC2BCB0; Wed, 6 May 2026 22:35:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778106903; bh=WfZgw+TSYwuuWZco9UUiaSzl0XhRcbOTgHLl0PrSIY0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=CpdjeXb6LhJnBfNGKPsNIwjICNhJmzQnnM8OOUFoISRbz87mMXevUCJKXaq6HiWE+ OmttBba0Yk/68exmOTloibYTblSSCl5EFCbxG5gY37AkPwPS9J4QTnmmvrALduwsqp ivZOwkUQcsZW89GcQtOT3tunEPunc7elJxHqmI0Ff/cvXMcEufWWfL6bAtTt8fhPfh BA/a4z/Oxi62zK9uK4KwgFcXWEIFaByo5n2FzjJXcxuwBlHF3YzRd4cWEqkvjUh6yS YHpVaKSfsJi0IAvCT4wh6F94bh0X8hJkNBkw09bfWTYZUTx/A5N9ulFskI7nl/OzxC 8FZZvzTxS7AAw== Date: Wed, 6 May 2026 15:35:02 -0700 From: Jakub Kicinski To: Paolo Abeni Cc: netdev@vger.kernel.org, edumazet@google.com, andrew+netdev@lunn.ch, horms@kernel.org, shuah@kernel.org, linux-kselftest@vger.kernel.org, davem@davemloft.net Subject: Re: [PATCH net 04/12] net: shaper: try to avoid violating RCU Message-ID: <20260506153502.57ffd9aa@kernel.org> In-Reply-To: References: <20260506000628.1501691-1-kuba@kernel.org> <20260506000628.1501691-5-kuba@kernel.org> <59b26f1e-efd5-488e-8738-15e96b9c79e4@redhat.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 6 May 2026 17:32:10 +0200 Paolo Abeni wrote: > On 5/6/26 5:22 PM, Paolo Abeni wrote: > > On 5/6/26 2:06 AM, Jakub Kicinski wrote: > >> net_shaper_commit() overrides nodes which may be concurrently read > >> under RCU. This is not a huge deal since the entries only contain > >> config, worst case user will see inconsistent config params. But > >> we should try to avoid this obvious RCU violation. Try to allocate > >> a new node. Since commit() can't fail fall back to overriding. > >> > >> Full fix is probably not worth the complexity, struct net_shaper > >> is around 80B, and the allocation is with GFP_KERNEL. > > > > I'm not sure if even this variant is worthy?!? The scheduler tree dump > > could be still inconsistent, as the dump is not atomic. IMHO e.g. > > inconsistent weights in the same WRR group would be as bad as > > inconsistent values inside the single shaper. > > I mean: I would simply avoid addressing this RCU violation. Alright. I'll add a comment instead (fix just the ordering WRT to the VALID flag)