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 D205220D51B for ; Fri, 25 Oct 2024 15:17:30 +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=1729869450; cv=none; b=NOc/gMk5xgXGzA4KJG+BK3fGBT52kojlPzEYSQbJTP5cQHP+iCBZ21ow1i0hEB/Rf5+kvjwFIZQD28M5nyg/idiYB9PaEyBSAVanimHDpTnxLu0BtP1N55tApnRb3QahwThM94P4mByZ3w9/nEbQXFsFAlykMGbF+RGapCfOeCQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729869450; c=relaxed/simple; bh=urfwP4uGmdRBzVymv5IfBHNWNqc7pqQaJUTDp03a5tM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lhIJlhTboX9tLrmrS98c/+4Z6qwXu4HUYABbwKijW5TZyL3/kixe6a3+9uuzdJnYn934ibzmPsBTyqvg4C4PVYmeVMUqy0fm3onzlZXMCwT+384BuQgZF1dLNxmXePwoJGUORoQJQWgGsWvbslWg0VpmyEpq52JjKvT4Qr7x/h8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QpyqBHiR; 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="QpyqBHiR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7622C4CEC3; Fri, 25 Oct 2024 15:17:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729869450; bh=urfwP4uGmdRBzVymv5IfBHNWNqc7pqQaJUTDp03a5tM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=QpyqBHiRreMPPw6gNh6ec5s7n+TjffglpAOlx40rQSeRC98HGG6IY+4frB1AHkMKw Y3n+MtvlBC3zqPiX7ZPRRzwK5dB+frpxLZtLkgFY0Ur3nfS7DLzUPlUCty+3uWrLt5 J36OWV0cxTAXSnuBzxL6+BnWiykUIiypXwiBKp3NsbUBH2DKXjMagvc0zqGo5POEzx KK0LmoB+Z6MKFovsBNgrYVxwic7WYqo4ONEmKDjLpx2Y/rw2I0aAy61hZdiFPd7pIa i5YiXUuga/6XL/P0hbBSztCFIqmSPv+cPbC7+PFYMtR9GDtLuXIPEV8H9uH4Za/k9r XLXQmfAGBJr/w== Message-ID: <3bc0cbec-e8d8-4981-8318-14976170d58e@kernel.org> Date: Fri, 25 Oct 2024 17:17:27 +0200 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH mptcp-net v2 2/3] mptcp: pm: lockless list traversal Content-Language: en-GB To: mptcp@lists.linux.dev Cc: Paolo Abeni References: <20241025-mptcp-pm-lookup_addr_rcu-v2-0-1478f6c4b205@kernel.org> <20241025-mptcp-pm-lookup_addr_rcu-v2-2-1478f6c4b205@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 25/10/2024 11:32, Matthieu Baerts (NGI0) wrote: > In a few places -- to get an endpoint, dump all of them, and change > their flags -- the list is iterated while holding the pernet->lock, but > only to read the content of the list. In these cases, we can replace the > spin locks, by RCU read ones, and use the _rcu variants to iterate over > the entries list in a lockless way. > > To make it clear, the lookup helpers using the _rcu variant are renamed > with a _rcu suffix. The previous __lookup_addr() helper can then be > removed, but __lookup_addr_by_id() is still needed. > > While at it, the IDs bitmap is copied before iterating the list to dump > the different addresses, to avoid any consistencies. > > Signed-off-by: Matthieu Baerts (NGI0) > --- > Notes: > - This is not a fix, a small improvement for -next. > --- > net/mptcp/pm_netlink.c | 36 +++++++++++++++++++----------------- > 1 file changed, 19 insertions(+), 17 deletions(-) > > diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c > index a93b9b7776b48781a883673fe5fd521a978487ff..f38e1ccd34e95cd88b179a8b50e6965731542871 100644 > --- a/net/mptcp/pm_netlink.c > +++ b/net/mptcp/pm_netlink.c > @@ -520,12 +520,12 @@ __lookup_addr_by_id(struct pm_nl_pernet *pernet, unsigned int id) > } > > static struct mptcp_pm_addr_entry * > -__lookup_addr(struct pm_nl_pernet *pernet, const struct mptcp_addr_info *info) > +__lookup_addr_by_id_rcu(struct pm_nl_pernet *pernet, unsigned int id) > { > struct mptcp_pm_addr_entry *entry; > > - list_for_each_entry(entry, &pernet->local_addr_list, list) { > - if (mptcp_addresses_equal(&entry->addr, info, entry->addr.port)) > + list_for_each_entry_rcu(entry, &pernet->local_addr_list, list) { I didn't see the following in the RCU doc -- but it is quite big, so I probably missed it -- but I suppose we don't need to keep the two helpers here with and without the _rcu variant (__lookup_addr_by_id()) if here we add an extra lockdep condition: list_for_each_entry_rcu(entry, &pernet->local_addr_list, list, lockdep_is_held(&pernet->lock)) { WDYT? > + if (entry->addr.id == id) > return entry; > } > return NULL; (...) > @@ -1872,16 +1872,18 @@ int mptcp_pm_nl_dump_addr(struct sk_buff *msg, > struct net *net = sock_net(msg->sk); > struct mptcp_pm_addr_entry *entry; > struct pm_nl_pernet *pernet; > + unsigned long id_bitmap[4]; Oops, I left my temp declaration, it should be the following line, which will result in the same thing anyway on x86_64, no need to re-run the tests → I can fix that when applying the patches, or in a future version: DECLARE_BITMAP(id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1); Cheers, Matt -- Sponsored by the NGI0 Core fund.