From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD150EB64DD for ; Thu, 27 Jul 2023 20:15:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232731AbjG0UP1 (ORCPT ); Thu, 27 Jul 2023 16:15:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46644 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230204AbjG0UPZ (ORCPT ); Thu, 27 Jul 2023 16:15:25 -0400 Received: from mail-pf1-x42b.google.com (mail-pf1-x42b.google.com [IPv6:2607:f8b0:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E337C1FDD; Thu, 27 Jul 2023 13:15:24 -0700 (PDT) Received: by mail-pf1-x42b.google.com with SMTP id d2e1a72fcca58-686b9920362so1089764b3a.1; Thu, 27 Jul 2023 13:15:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1690488924; x=1691093724; h=content-transfer-encoding:mime-version:subject:references :in-reply-to:message-id:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=5pjZ51xtViHPu61r/EFWrYe+qxWhroS6JQ+9gaxVDaQ=; b=AhyHSKUIkkgbZvtQQcyOKRC4C+sGBBU1rnW7UKRYJelhzH7/ZrA6+1Xg4/vOjR9OBb 2LiXllBWDr3LkIBs0B/HpC95oZnJRCD0J4e6Qd/+w+xbPyfsCkd+ypfy8zlEEQg2Cs2l 1bNXUidT+UahwU+1TAhT92SRQd4PrYR4jj1FwXZuZrdtDG/PyKSc/2Cj5pi/joFqabur JkmKOL1V/ewlylT3LCRSl78qgYZTBnWSXDg0te4dPPC4jPB3EFA+GB1EhGkQOlrFtEFQ b4MraEAS4OuOvFpd4YQIPbgaCFLUB+9vO60R9LnsWln7xCCnmoiYLosUxYKJ4hpTpGB3 IMIQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690488924; x=1691093724; h=content-transfer-encoding:mime-version:subject:references :in-reply-to:message-id:cc:to:from:date:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=5pjZ51xtViHPu61r/EFWrYe+qxWhroS6JQ+9gaxVDaQ=; b=gtaaOTcsrMrErlKyvsUhYNJ6UxEkH2T7pnO/ageJcMbL2aF+Ewt0k9LbF6STUwLvji SJiiGQtcDP81BtECOBlICJaP9dBa7Wkd76ztOkExyx7pM1Kosu2GyGdM+weeySeQG5Qc bank9xEjwwnEUnqCp0H4pgJzDbxhFQpk2ETt1X/xI6XhdQzp88xn7IJdNRmFro7npkfg 4UDeETbg73Uuizjg0T5ymiXrtCKIJh6XgIhWTn9TWWwDtWhA70jTXXKWlru0uaeOJczq aKCwFmB2hZpcCM+qBVeqa0+VSXARwU6y4N1s44GzBjc/UothsnwfYy0b8QCTFFM8TuRM ohqQ== X-Gm-Message-State: ABy/qLYz+eRBc5J7pvbmy2hRhOhWNdPbI/cBBqARlDTWSJWYNepniGyX KXUMwWw3yI0oq56EwXtK7aE= X-Google-Smtp-Source: APBJJlE/vCxhHaS86mEOqx3kFx6vMxKfngxzPSkTcBkc7tZIAXfeUFlJDQsMA7TZxE9/hIrOlKW7eg== X-Received: by 2002:a05:6a20:7351:b0:133:656e:fe1e with SMTP id v17-20020a056a20735100b00133656efe1emr128808pzc.47.1690488924247; Thu, 27 Jul 2023 13:15:24 -0700 (PDT) Received: from localhost ([2605:59c8:148:ba10:705d:54ca:a48d:47da]) by smtp.gmail.com with ESMTPSA id m17-20020aa78a11000000b0063afb08afeesm1862257pfa.67.2023.07.27.13.15.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Jul 2023 13:15:23 -0700 (PDT) Date: Thu, 27 Jul 2023 13:15:22 -0700 From: John Fastabend To: tglozar@redhat.com, linux-kernel@vger.kernel.org Cc: john.fastabend@gmail.com, jakub@cloudflare.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, bpf@vger.kernel.org, Tomas Glozar Message-ID: <64c2d05a894be_831d20896@john.notmuch> In-Reply-To: <20230726085003.261112-1-tglozar@redhat.com> References: <20230726085003.261112-1-tglozar@redhat.com> Subject: RE: [PATCH RFC net] bpf: sockmap: Remove preempt_disable in sock_map_sk_acquire Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org tglozar@ wrote: > From: Tomas Glozar > > Disabling preemption in sock_map_sk_acquire conflicts with GFP_ATOMIC > allocation later in sk_psock_init_link on PREEMPT_RT kernels, since > GFP_ATOMIC might sleep on RT (see bpf: Make BPF and PREEMPT_RT co-exist > patchset notes for details). > > This causes calling bpf_map_update_elem on BPF_MAP_TYPE_SOCKMAP maps to > BUG (sleeping function called from invalid context) on RT kernels. > > preempt_disable was introduced together with lock_sk and rcu_read_lock > in commit 99ba2b5aba24e ("bpf: sockhash, disallow bpf_tcp_close and update > in parallel") with no comment on why it is necessary. > > Remove preempt_disable to fix BUG in sock_map_update_common on RT. > > Signed-off-by: Tomas Glozar > --- > net/core/sock_map.c | 2 -- > 1 file changed, 2 deletions(-) Hi Thomas, I looked at this and don't see the need for the preempt_disable there at the moment. I believe it was there simply to match the BPF caller case where it was preempt_disable at the time and now is migrate disable. From the BPF side we don't want the migrate, but from the syscall interface it should be OK. Can you submit without RFC tag I think this should be OK. Thanks, John > > diff --git a/net/core/sock_map.c b/net/core/sock_map.c > index 19538d628714..08ab108206bf 100644 > --- a/net/core/sock_map.c > +++ b/net/core/sock_map.c > @@ -115,7 +115,6 @@ static void sock_map_sk_acquire(struct sock *sk) > __acquires(&sk->sk_lock.slock) > { > lock_sock(sk); > - preempt_disable(); > rcu_read_lock(); > } > > @@ -123,7 +122,6 @@ static void sock_map_sk_release(struct sock *sk) > __releases(&sk->sk_lock.slock) > { > rcu_read_unlock(); > - preempt_enable(); > release_sock(sk); > } > > > base-commit: 22117b3ae6e37d07225653d9ae5ae86b3a54f99c > -- > 2.39.3 >