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=-9.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 958EAC433DF for ; Wed, 14 Oct 2020 16:32:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3CC42214D8 for ; Wed, 14 Oct 2020 16:32:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="nCeMhgku" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388200AbgJNQck (ORCPT ); Wed, 14 Oct 2020 12:32:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50576 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731028AbgJNQck (ORCPT ); Wed, 14 Oct 2020 12:32:40 -0400 Received: from mail-io1-xd42.google.com (mail-io1-xd42.google.com [IPv6:2607:f8b0:4864:20::d42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E4A7AC061755 for ; Wed, 14 Oct 2020 09:32:39 -0700 (PDT) Received: by mail-io1-xd42.google.com with SMTP id n6so5909455ioc.12 for ; Wed, 14 Oct 2020 09:32:39 -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=8B1b67LV7GcK3X+6yPNOWg/2xf6f4j15sYSu/rEI0pQ=; b=nCeMhgkuY5i99JMaskXEuSDVWP+iH45vJfGnX9EdydvztWBJ6XGVQeQDA/BQU9cGj6 wr5u9ec+UWlbcs1LUumE8haPpoQMpAPaO8+9kXcD8gGzX1rYF2CjMpwMFxskcG9WtoEk l4XeT5NxohuwafKO05cvfbTfGCjpOgz7+hs9jThItgq+by2oOB8Whcqrh6KX52GjtQ5Z MA5BIe/ZljUfWNBLpmpNjN4b+d3BtU+bH+t6WHWqAAu+2NTRj2kRumFjIsiQ9ETTfvEr iiu+XkKnq/ONL5HMajsRRoN0diRgTVQrWRi/ADz94BmpKyg4gJF9hrhrhNLBEPfiOtO2 KR/w== 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=8B1b67LV7GcK3X+6yPNOWg/2xf6f4j15sYSu/rEI0pQ=; b=iYtCmmDbLp/xlvs0A5e7oUqL1QC4LI3PokLlnPE28rBuMg5gQUFxPj4X6Otme1F18q RaZjdFCjVVGCd5o+W0ZON8sfdvcnP5ALxIcmzIHHHlB48TOnXLy3b5lV5HskuzOG02+B Ix+3X1exYGI01mF4ylSoxWBppVsf+vAKgz8J8jnUV9Es1jfXJvvX67g9wzpz6Z1pe6ru usmQMwfNMloGh8/aJjBoXTPDnC3f33x+F94ANeHyVCawFyHqErnxWurhi5tumHAy5Ybm 2Ge/J/LTHEQPg7UBEVP6OGx6+0lADxaZUTEfRl6Ia+xSN4svkl5E9c6OyYjA45l5pPy0 M/sA== X-Gm-Message-State: AOAM530htL4voubsMOoUn7+Pscviy8a2zGuV5T+rLoTDNDRqXdoVqmQ4 9rFfhP3lz04mojvT9af+RSsUM/ickX+nSe8e61N17dGxzVsxNg== X-Google-Smtp-Source: ABdhPJzzVmbDuxvQwoFcnGQf8XBzcUnBjTYFYc01UCjxLnn0AgTPCd+NyBvYp2/khPyqOG9Nt1+MEyiI4Iq8u96f7h0= X-Received: by 2002:a05:6602:144:: with SMTP id v4mr126076iot.115.1602693159333; Wed, 14 Oct 2020 09:32:39 -0700 (PDT) MIME-Version: 1.0 References: <20201014151614.29804-1-hqjagain@gmail.com> <20201014113823.4296521d@gandalf.local.home> <20201014121136.042a5c37@gandalf.local.home> In-Reply-To: <20201014121136.042a5c37@gandalf.local.home> From: Qiujun Huang Date: Thu, 15 Oct 2020 00:32:28 +0800 Message-ID: Subject: Re: [PATCH] ring-buffer: Add rb_check_bpage in __rb_allocate_pages To: Steven Rostedt Cc: mingo@redhat.com, LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 15, 2020 at 12:11 AM Steven Rostedt wrote: > > On Wed, 14 Oct 2020 23:48:05 +0800 > Qiujun Huang wrote: > > > On Wed, Oct 14, 2020 at 11:38 PM Steven Rostedt wrote: > > > > > > On Wed, 14 Oct 2020 23:16:14 +0800 > > > Qiujun Huang wrote: > > > > > > > It may be better to check each page is aligned by 4 bytes. The 2 > > > > least significant bits of the address will be used as flags. > > > > > > > > Signed-off-by: Qiujun Huang > > > > --- > > > > kernel/trace/ring_buffer.c | 11 +++++++---- > > > > 1 file changed, 7 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > > > > index 93ef0ab6ea20..9dec7d58b177 100644 > > > > --- a/kernel/trace/ring_buffer.c > > > > +++ b/kernel/trace/ring_buffer.c > > > > @@ -1420,7 +1420,8 @@ static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) > > > > return 0; > > > > } > > > > > > > > -static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu) > > > > +static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, > > > > + long nr_pages, struct list_head *pages, int cpu) > > > > { > > > > struct buffer_page *bpage, *tmp; > > > > bool user_thread = current->mm != NULL; > > > > @@ -1464,6 +1465,8 @@ static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu) > > > > if (!bpage) > > > > goto free_pages; > > > > > > > > + rb_check_bpage(cpu_buffer, bpage); > > > > + > > > > > > > > > > Why add it here, and not just add this check to the scan in > > > rb_check_pages()? > > > > rb_head_page_deactivate() in rb_check_pages() will clear the 2 LSB first. > > > > Well, you could just add another scan there, but if you want to do it this > way, then remove passing the int cpu to these functions, and use the > cpu_buffer->cpu, as keeping the cpu is just redundant. Get it. > > Also, did you see an issue? This check is more of me being paranoid to No, I'm a little paranoid too following the code :-) > make sure we don't crash later. I've honestly never seen it trigger. > > -- Steve