linux-kernel - Re: [Xen-devel] [PATCH 5/6] xenbus: process be

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Date:   Fri, 14 Sep 2018 16:26:37 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Dongli Zhang <dongli.zhang@...cle.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Cc:     wei.liu2@...rix.com, konrad.wilk@...cle.com,
        srinivas.eeda@...cle.com, paul.durrant@...rix.com,
        boris.ostrovsky@...cle.com, roger.pau@...rix.com
Subject: Re: [Xen-devel] [PATCH 5/6] xenbus: process be_watch events in
 xenwatch multithreading

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/<pvdev>/<domid>i/...' can be processed in per-domU xenwatch
>>
>> superfluous "i" ----------^
>>
>>> thread.
>>>
>>> Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>
>>> ---
>>>  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()?


Juergen