From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f51.google.com (mail-lf1-f51.google.com [209.85.167.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB1D73403FC for ; Tue, 19 May 2026 13:06:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779195977; cv=none; b=t9XpMAJDqOuz+GoggrmJIxHY/vFhYX8LmI9Dl0WLCI6Key4DMPoPW7RYUmZfZLxT5cfwT3csvdH/DUROm+EZuNEhE90UK6TpzFBQRj8S9XCK2vNkiQGzLTbiHyWBHZXckY807E9L9+K9mYDPX8M6Kdcn20xJ/oF/C0WHfM5kY/M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779195977; c=relaxed/simple; bh=cg4z7G7iNBSO9WPLaSxyK3mhnsTtEoKLiHUito40w9U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UhgS6friacAMzPZoSAxeD9BEi0pDbxMFkaU8JK5nZs74eyMBZSRv/YnT6CkS411kFLTGuNrwEFRnv7ZoLGgHoaAN6NlFS7jJ/77qdfcIvQ5GAGL1gN8GmjlzM5rRJ12MuQEwkGl2kilyg1lcvBNjwehb3EUjDi4Pm8iSlJYzmTU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=blackwall.org; spf=none smtp.mailfrom=blackwall.org; dkim=pass (2048-bit key) header.d=blackwall.org header.i=@blackwall.org header.b=kwXBGbji; arc=none smtp.client-ip=209.85.167.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=blackwall.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=blackwall.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=blackwall.org header.i=@blackwall.org header.b="kwXBGbji" Received: by mail-lf1-f51.google.com with SMTP id 2adb3069b0e04-5a8fbe18b1dso6017406e87.2 for ; Tue, 19 May 2026 06:06:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=blackwall.org; s=google; t=1779195974; x=1779800774; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=mBDmsIRaLxU1htRPlExjpxjIYZQeUV/LcGzok6vPGGI=; b=kwXBGbjiqKL80cPycnq0bJj0qNvwKq+TrenGRUW0bjWmNDdZhDsHgxuYXhzEL9tZQN q7Liw5l6DLYZdsD4Azs/D3o4r0stvUnvR0Hgpt+rosIX+B1lIEOT/IKAW2gHwnUMRgft 1euULnig2fCtGImNof/t+O/M+XZ23xnZ9fbNr3Z0k0olPbeFsgpWDuUW1l76AiUy+56L g/HDaOZu8IovYijPLhxGCfiJacQYxIK+ihL+UqPK66aeDEMpRL0/V1cUQZhj3G3krWpJ a6lV/S7IzdtS+Hb+gPiquLG2HAgB/jYTJIEK9sq5GmKT/o00lytsDX/rNFdemZyXYEEZ YjDQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779195974; x=1779800774; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=mBDmsIRaLxU1htRPlExjpxjIYZQeUV/LcGzok6vPGGI=; b=V9wuVjzF1ndowA6GZN8CwBUI7Hv6X4zpL7+MzuJ7rYzyk2iTsZMidiSgY8kw3JfL5D LVK2ydwq9TXHFShT9NApPBTpMlJY8J0FXkvAO5ULUH2ZEYbqg/QA8cG49PdEUp1BN039 +5AAqq1P/+8ipa+7woNjM0Ymyl82T77Vn6n1SmML6CcgpqiYlWK3EYz+A01FTwnaUW8S n0QNh91c4LQB71BKlIliu1cKehRfoorgNmdVJxz2oNu+p2cKixI5RNP7taXSgJRzSg0C E11kEvERHp5OjyUuPKJw5qq6vcw1LFiidc+FQw5vaCKcN0FTu6LO+U2h4QRzgNmACZl1 /CsQ== X-Forwarded-Encrypted: i=1; AFNElJ8Vt0Kb0xjDzuR82rtRpCw5FMFDAkuBYlvjxbX1amAKwQRpQBGWdeAIDoBhnOGFrlIOa1YXEB8=@vger.kernel.org X-Gm-Message-State: AOJu0Yx2cEl3lzk1hIdnfT9QhzBQBZ9LuUDVWO0iitdH6nG0ZPZ2Qxei RS2sIXzfjEg3PRSR4aVct5Bb2HkQXp2/M+3ik/ZALXMGo3IsaJjNFXZ+N3Bhh5Z/mX8mpjBIRnn euCoh X-Gm-Gg: Acq92OEBV1/zKKydIEr2hk5wdtngM9WIE1rEoBAsHn5BcItkBacAjlVNYTb//Uhp7cT GNswWyHW+RdAgKhv86uUibevWENPGRCPGB5TgOf19Hq/MACTlBMoWN6lgXyMXAkA7Mzh5vxtrTQ 6+XUEQBj+XrDgThWhTG54XwGV+rEqiIYnH7Q7OKUucstw+7gQepQMSYIeRcobbMlZswpMX5KO4T 6JNPJDV7VjTERWTnoKDEJKNnJuz0W1+1oQ7iMNo3/XvcfmsvakQtAIoTzsCNxXCNohCvdSWmmln 0FnLDykFTqWbJ/EpOwKUS6BtADeoBJ02LrxgkcN0kGrr5KFFqKPyM4Qw5A/1xYkOyEU+QqMjrVP M6jKq26j8lG/421FN5UbIvWX3GJDjefFSFc63nGBHuRI2AZhEwqTGzhgRw1qIigd0fGmjIkEf0F 5cnNQf2CJKPZaGVNJO4ffj4WNNQZK/G2ki24wdLzSmLA== X-Received: by 2002:a05:6512:1321:b0:5a8:8df1:61bf with SMTP id 2adb3069b0e04-5aa0e763a62mr5665485e87.21.1779195973589; Tue, 19 May 2026 06:06:13 -0700 (PDT) Received: from localhost ([176.111.181.159]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a9164c5a36sm4124074e87.60.2026.05.19.06.06.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 May 2026 06:06:13 -0700 (PDT) Date: Tue, 19 May 2026 16:06:06 +0300 From: Nikolay Aleksandrov To: Eric Dumazet Cc: "David S . Miller" , Jakub Kicinski , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, eric.dumazet@gmail.com, Ido Schimmel Subject: Re: [PATCH net-next] net: bridge: remove stale rcu_barrier() in br_multicast_dev_del() Message-ID: References: <20260519095540.2643318-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260519095540.2643318-1-edumazet@google.com> On Tue, May 19, 2026 at 09:55:40AM +0000, Eric Dumazet wrote: > This rcu_barrier() came from a time call_rcu() calls were used in > net/bridge/br_multicast.c. > > Now kfree_rcu() is there, we can remove this problematic rcu_barrier() > which causes extreme RTNL pressure in many syzbot reports. > > INFO: task syz-executor:77945 is blocked on a mutex likely owned by task kworker/u1024:5:36537. > task:kworker/u1024:5 state:D stack:24616 pid:36537 tgid:36537 ppid:2 task_flags:0x4208060 flags:0x00080000 last_sleep:612797637337 > Workqueue: netns cleanup_net > Call Trace: > > [] context_switch+0xf2a/0x1730 kernel/sched/core.c:6483 > [] __schedule+0x1133/0x43a0 kernel/sched/core.c:8411 > [] __schedule_loop kernel/sched/core.c:8514 [inline] > [] schedule+0xab/0x260 kernel/sched/core.c:8529 > [] schedule_timeout+0xc3/0x2b0 kernel/time/sleep_timeout.c:75 > [] do_wait_for_common kernel/sched/completion.c:100 [inline] > [] __wait_for_common kernel/sched/completion.c:121 [inline] > [] wait_for_common kernel/sched/completion.c:132 [inline] > [] wait_for_completion+0x2c7/0x5d0 kernel/sched/completion.c:153 > [] rcu_barrier+0x49f/0x620 kernel/rcu/tree.c:3888 > [] br_multicast_dev_del+0x303/0x350 net/bridge/br_multicast.c:4459 > [] br_dev_uninit+0x1c/0x40 net/bridge/br_device.c:157 > [] unregister_netdevice_many_notify+0x1c1c/0x2300 net/core/dev.c:12599 > [] ops_exit_rtnl_list net/core/net_namespace.c:187 [inline] > [] ops_undo_list+0x3d3/0x940 net/core/net_namespace.c:248 > > Signed-off-by: Eric Dumazet > --- > Cc: Nikolay Aleksandrov > Cc: Ido Schimmel > --- > net/bridge/br_multicast.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c > index 49ceea3ff9742d3043ac605d656b7fcf37dbcb96..8efa3add5d47508fb2b032ff6238ffbbabfd27ad 100644 > --- a/net/bridge/br_multicast.c > +++ b/net/bridge/br_multicast.c > @@ -4453,8 +4453,6 @@ void br_multicast_dev_del(struct net_bridge *br) > br_multicast_ctx_deinit(&br->multicast_ctx); > br_multicast_gc(&deleted_head); > cancel_work_sync(&br->mcast_gc_work); > - > - rcu_barrier(); > } > > int br_multicast_set_router(struct net_bridge_mcast *brmctx, unsigned long val) > -- > 2.54.0.563.g4f69b47b94-goog > Acked-by: Nikolay Aleksandrov