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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87138C433DF for ; Tue, 18 Aug 2020 17:07:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4314E20786 for ; Tue, 18 Aug 2020 17:07:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="QvghSaoi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728553AbgHRRHV (ORCPT ); Tue, 18 Aug 2020 13:07:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728529AbgHRRHB (ORCPT ); Tue, 18 Aug 2020 13:07:01 -0400 Received: from mail-lj1-x244.google.com (mail-lj1-x244.google.com [IPv6:2a00:1450:4864:20::244]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 283ECC061389; Tue, 18 Aug 2020 10:07:00 -0700 (PDT) Received: by mail-lj1-x244.google.com with SMTP id v12so22253009ljc.10; Tue, 18 Aug 2020 10:07:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=C1c/4yYVQMz5AXCBeUFg3WeRQ4gJyBE8RLv9ILCFc0o=; b=QvghSaoinoGGEoblQhcc781ePNo6gwt6MuJSI3NIScgE+n9xRSfVF5USpt6fHYkQfx NS43fpPE3KciwhmCAqOdIcDekVhipGjwAiIjuKhISbystiv4TcP359qcWiCCMsedw4KO ctdVBY09AfDpUy3FV3Rq8LXrF/8AsNkej9Ws7i35qQl0Q0gnPygTQviqYfML/PhGOKgO mvmW/nATUYaIkQ4Pd6Hvi2qi2oLOWimYK0KUusEL9Wdj1eY0nQtPjBT44Hm00MTxLSwZ KIn4ddBAhdGYClkYUjW9Xmx4L+P4R1eBQT3lWmGRIeOqRHV5bEH6m3UKpnFWMD4/Zttb TLCw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=C1c/4yYVQMz5AXCBeUFg3WeRQ4gJyBE8RLv9ILCFc0o=; b=LSFocWq0ZnZTKNK7Gke3ybNA8001u3ZYNIfXPMlWntfrtkNsZjfnj2EeRF+DqWCpdT xSe+qOy62sLvCB6/XYgWV76P9CnLdCwpdvSf6VWiZXWO3d5fzfnjJNVrchJBv7AfNv64 l2Mnsm+8hso7H9W2BECIGtU6EI7rx6VD59d7aY8m/IiMnVsxUd5GpsbCbu5H35OoQ83X Hz/3Q4bAKu/xyMJqCHurGN07sdoW4YkgW89jS8DedMh7WNYPsIdNWKtzfMYKsfgzNwDi 1tL3N7wncZ/MjyPmcqoHwDPB24tF3x1f1tbNTMJykZiSVIMSbYkljL6AmG1GMdd6UqoJ p89w== X-Gm-Message-State: AOAM531HDDpmfh0oUquO7mOyodylNsuJ1u7z8a/BmB75fTiNqeNMPvrG 7SRUiSMmhEMeV2ItS8kVz2mjFACKVMw4EQoRHxA= X-Google-Smtp-Source: ABdhPJxfJlqVZNsDe12u4bVbuOkl3hOs64lMGe8ZJvh0aMYrK8khzErkDso/qwds4PALzJ+TFNKE4J98b6BbuAHAZqg= X-Received: by 2002:a2e:8e28:: with SMTP id r8mr9576006ljk.290.1597770418614; Tue, 18 Aug 2020 10:06:58 -0700 (PDT) MIME-Version: 1.0 References: <20200818162408.836759-1-yhs@fb.com> <20200818162408.836816-1-yhs@fb.com> In-Reply-To: <20200818162408.836816-1-yhs@fb.com> From: Alexei Starovoitov Date: Tue, 18 Aug 2020 10:06:47 -0700 Message-ID: Subject: Re: [PATCH bpf 1/2] bpf: fix a rcu_sched stall issue with bpf task/task_file iterator To: Yonghong Song Cc: bpf , Network Development , Alexei Starovoitov , Daniel Borkmann , Kernel Team , "Paul E . McKenney" Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Aug 18, 2020 at 9:24 AM Yonghong Song wrote: > index f21b5e1e4540..885b14cab2c0 100644 > --- a/kernel/bpf/task_iter.c > +++ b/kernel/bpf/task_iter.c > @@ -27,6 +27,8 @@ static struct task_struct *task_seq_get_next(struct pid_namespace *ns, > struct task_struct *task = NULL; > struct pid *pid; > > + cond_resched(); > + > rcu_read_lock(); > retry: > pid = idr_get_next(&ns->idr, tid); > @@ -137,6 +139,8 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info, > struct task_struct *curr_task; > int curr_fd = info->fd; > > + cond_resched(); > + Instead of adding it to every *seq_get_next() it probably should be in bpf_seq_read(). If cond_resched() is needed in task_file_seq_get_next() it should probably be after 'again:'.