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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 116C5C433F4 for ; Wed, 19 Sep 2018 08:01:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC896208A3 for ; Wed, 19 Sep 2018 08:01:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BC896208A3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731001AbeISNi0 (ORCPT ); Wed, 19 Sep 2018 09:38:26 -0400 Received: from mx2.suse.de ([195.135.220.15]:44140 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726527AbeISNiZ (ORCPT ); Wed, 19 Sep 2018 09:38:25 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id C26F8ADF7; Wed, 19 Sep 2018 08:01:38 +0000 (UTC) Subject: Re: [Xen-devel] [PATCH 5/6] xenbus: process be_watch events in xenwatch multithreading To: Dongli Zhang , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Cc: wei.liu2@citrix.com, konrad.wilk@oracle.com, srinivas.eeda@oracle.com, paul.durrant@citrix.com, boris.ostrovsky@oracle.com, roger.pau@citrix.com References: <1536910456-13337-1-git-send-email-dongli.zhang@oracle.com> <1536910456-13337-6-git-send-email-dongli.zhang@oracle.com> <8d6457cf-a105-3d88-bd38-d46b24f70501@suse.com> <8f4c7508-1e8f-9d7e-1327-f537917845f4@oracle.com> <0753b7b8-31a6-22f5-479a-2760fea0149c@oracle.com> <62194cbd-be25-fc2e-f115-5111888d7bc6@suse.com> <7fec0ad1-84e5-f490-d196-623a8b3685ac@oracle.com> From: Juergen Gross Openpgp: preference=signencrypt Autocrypt: addr=jgross@suse.com; prefer-encrypt=mutual; keydata= xsBNBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOB ycWxw3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJve dYm8Of8Zd621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJ NwQpd369y9bfIhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvx XP3FAp2pkW0xqG7/377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEB AAHNHkp1ZXJnZW4gR3Jvc3MgPGpncm9zc0BzdXNlLmRlPsLAeQQTAQIAIwUCU4xw6wIbAwcL CQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJELDendYovxMvi4UH/Ri+OXlObzqMANruTd4N zmVBAZgx1VW6jLc8JZjQuJPSsd/a+bNr3BZeLV6lu4Pf1Yl2Log129EX1KWYiFFvPbIiq5M5 kOXTO8Eas4CaScCvAZ9jCMQCgK3pFqYgirwTgfwnPtxFxO/F3ZcS8jovza5khkSKL9JGq8Nk czDTruQ/oy0WUHdUr9uwEfiD9yPFOGqp4S6cISuzBMvaAiC5YGdUGXuPZKXLpnGSjkZswUzY d9BVSitRL5ldsQCg6GhDoEAeIhUC4SQnT9SOWkoDOSFRXZ+7+WIBGLiWMd+yKDdRG5RyP/8f 3tgGiB6cyuYfPDRGsELGjUaTUq3H2xZgIPfOwE0EU4xwFgEIAMsx+gDjgzAY4H1hPVXgoLK8 B93sTQFN9oC6tsb46VpxyLPfJ3T1A6Z6MVkLoCejKTJ3K9MUsBZhxIJ0hIyvzwI6aYJsnOew cCiCN7FeKJ/oA1RSUemPGUcIJwQuZlTOiY0OcQ5PFkV5YxMUX1F/aTYXROXgTmSaw0aC1Jpo w7Ss1mg4SIP/tR88/d1+HwkJDVW1RSxC1PWzGizwRv8eauImGdpNnseneO2BNWRXTJumAWDD pYxpGSsGHXuZXTPZqOOZpsHtInFyi5KRHSFyk2Xigzvh3b9WqhbgHHHE4PUVw0I5sIQt8hJq 5nH5dPqz4ITtCL9zjiJsExHuHKN3NZsAEQEAAcLAXwQYAQIACQUCU4xwFgIbDAAKCRCw3p3W KL8TL0P4B/9YWver5uD/y/m0KScK2f3Z3mXJhME23vGBbMNlfwbr+meDMrJZ950CuWWnQ+d+ Ahe0w1X7e3wuLVODzjcReQ/v7b4JD3wwHxe+88tgB9byc0NXzlPJWBaWV01yB2/uefVKryAf AHYEd0gCRhx7eESgNBe3+YqWAQawunMlycsqKa09dBDL1PFRosF708ic9346GLHRc6Vj5SRA UTHnQqLetIOXZm3a2eQ1gpQK9MmruO86Vo93p39bS1mqnLLspVrL4rhoyhsOyh0Hd28QCzpJ wKeHTd0MAWAirmewHXWPco8p1Wg+V+5xfZzuQY0f4tQxvOpXpt4gQ1817GQ5/Ed/wsDtBBgB CAAgFiEEhRJncuj2BJSl0Jf3sN6d1ii/Ey8FAlrd8NACGwIAgQkQsN6d1ii/Ey92IAQZFggA HRYhBFMtsHpB9jjzHji4HoBcYbtP2GO+BQJa3fDQAAoJEIBcYbtP2GO+TYsA/30H/0V6cr/W V+J/FCayg6uNtm3MJLo4rE+o4sdpjjsGAQCooqffpgA+luTT13YZNV62hAnCLKXH9n3+ZAgJ RtAyDWk1B/0SMDVs1wxufMkKC3Q/1D3BYIvBlrTVKdBYXPxngcRoqV2J77lscEvkLNUGsu/z W2pf7+P3mWWlrPMJdlbax00vevyBeqtqNKjHstHatgMZ2W0CFC4hJ3YEetuRBURYPiGzuJXU pAd7a7BdsqWC4o+GTm5tnGrCyD+4gfDSpkOT53S/GNO07YkPkm/8J4OBoFfgSaCnQ1izwgJQ jIpcG2fPCI2/hxf2oqXPYbKr1v4Z1wthmoyUgGN0LPTIm+B5vdY82wI5qe9uN6UOGyTH2B3p hRQUWqCwu2sqkI3LLbTdrnyDZaixT2T0f4tyF5Lfs+Ha8xVMhIyzNb1byDI5FKCb Message-ID: <91cfb61b-5413-2811-771b-b3860f626010@suse.com> Date: Wed, 19 Sep 2018 10:01:36 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <7fec0ad1-84e5-f490-d196-623a8b3685ac@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: de-DE Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/09/18 08:15, Dongli Zhang wrote: > Hi Juergen, > > On 09/14/2018 10:44 PM, Juergen Gross wrote: >> On 14/09/18 16:29, Dongli Zhang wrote: >>> Hi Juergen, >>> >>> On 09/14/2018 10:26 PM, Juergen Gross wrote: >>>> On 14/09/18 16:18, Dongli Zhang wrote: >>>>> Hi Juergen, >>>>> >>>>> On 09/14/2018 05:12 PM, Juergen Gross wrote: >>>>>> On 14/09/18 09:34, Dongli Zhang wrote: >>>>>>> This is the 5th patch of a (6-patch) patch set. >>>>>>> >>>>>>> With this patch, watch event in relative path pattern >>>>>>> 'backend//i/...' can be processed in per-domU xenwatch >>>>>> >>>>>> superfluous "i" ----------^ >>>>>> >>>>>>> thread. >>>>>>> >>>>>>> Signed-off-by: Dongli Zhang >>>>>>> --- >>>>>>> drivers/xen/xenbus/xenbus_probe.c | 2 +- >>>>>>> drivers/xen/xenbus/xenbus_probe_backend.c | 32 +++++++++++++++++++++++++++++++ >>>>>>> include/xen/xenbus.h | 2 ++ >>>>>>> 3 files changed, 35 insertions(+), 1 deletion(-) >>>>>>> >>>>>>> diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c >>>>>>> index ba0644c..aa1b15a 100644 >>>>>>> --- a/drivers/xen/xenbus/xenbus_probe.c >>>>>>> +++ b/drivers/xen/xenbus/xenbus_probe.c >>>>>>> @@ -552,7 +552,7 @@ int xenbus_probe_devices(struct xen_bus_type *bus) >>>>>>> } >>>>>>> EXPORT_SYMBOL_GPL(xenbus_probe_devices); >>>>>>> >>>>>>> -static unsigned int char_count(const char *str, char c) >>>>>>> +unsigned int char_count(const char *str, char c) >>>>>> >>>>>> Please change the name of the function when making it globally >>>>>> visible, e.g. by prefixing "xenbus_". >>>>>> >>>>>> Generally I think you don't need to use it below. >>>>>> >>>>>>> { >>>>>>> unsigned int i, ret = 0; >>>>>>> >>>>>>> diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c >>>>>>> index b0bed4f..50df86a 100644 >>>>>>> --- a/drivers/xen/xenbus/xenbus_probe_backend.c >>>>>>> +++ b/drivers/xen/xenbus/xenbus_probe_backend.c >>>>>>> @@ -211,9 +211,41 @@ static void backend_changed(struct xenbus_watch *watch, >>>>>>> xenbus_dev_changed(path, &xenbus_backend); >>>>>>> } >>>>>>> >>>>>>> +static domid_t path_to_domid(const char *path) >>>>>>> +{ >>>>>>> + const char *p = path; >>>>>>> + domid_t domid = 0; >>>>>>> + >>>>>>> + while (*p) { >>>>>>> + if (*p < '0' || *p > '9') >>>>>>> + break; >>>>>>> + domid = (domid << 3) + (domid << 1) + (*p - '0'); >>>>>> >>>>>> reinventing atoi()? >>>>>> >>>>>> Please don't do that. kstrtou16() seems to be a perfect fit. >>>>> >>>>> I did use kstrtou*() in the early prototype and realized kstrtou16() returns 0 >>>>> if the input string contains non-numerical characters. >>>>> >>>>> E.g., the example of input can be "1/0/state", where 1 is fotherend_id >>>>> (frontend_id) and 0 is handle. >>>>> >>>>> When "1/0/state" is used at input, kstrtou16() returns 0 (returned integer) and >>>>> -22 (error). >>>> >>>> Aah, okay. Then simple_strtoul()? >>> >>> I did consider simple_strtoul() initially. Unfortunately, it is obsolete (below >>> line 81). AFAIR, the patch would not be able to pass the check_patch script when >>> this function is used. >> >> Better use that than open coding a new instance of it. >> >> Another variant would be to use sscanf() or similar. Then you could even >> drop using strchr() by adding that in the format string: >> >> return (sscanf(path, "%*u/%u/", &domid) == 1) ? domid : DOMID_SELF; > > I recall what was happened. > > Suppose one sample of path is "backend/vif/19/3/state". (we would like to obtain > domid=19) > > Initially I would like to use sscanf(path, "backend/%*[a-z]/%hu/%*u") to obtain > the domid from xenstore path in one call. > > Unfortunately, unlike userspace sscanf(), the version in linux kernel does not > support '[' so that I would not be able to use "%*[a-z]" in sscanf() in linux > kernel. That is not correct. It doesn't support ranges in [], but it is perfectly fine to use %[^/]. This requires a temporary buffer, as %*[ isn't supported. Why don't you use: char temp[16]; ... /* kernel sscanf() %[] doesn't support '*' modifier and needs length. */ sscanf(path, "backend/%15[^/]%hu/%*u", temp, &domid) Juergen