Re: [dpdk-dev] [PATCH] net/tap: avoid using SIGIO

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 7/28/2020 11:48 AM, Morten Brørup wrote:
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen Hemminger
>> Sent: Monday, July 27, 2020 9:44 PM
>>
>> On Mon, 27 Jul 2020 15:19:32 +0200
>> Morten Brørup <mb@smartsharesystems.com> wrote:
>>
>>>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen
>> Hemminger
>>>> Sent: Wednesday, July 15, 2020 1:58 AM
>>>>
>>>> SIGIO maybe used by application, instead choose another rt-signal.
>>>> Linux allows any signal to be used for signal based IO.
>>>> Search for an unused signal in the available rt-signal range.
>>>
>>> Just an observation. Feel free to ignore at your convenience:
>>>
>>> The problem is the same as for SIGIO if the application sets up its
>> own signal handler after this, and uses some hardcoded rt-signal that
>> happens to be the one found to be free.
>>>
>>> Unless the application doesn't use a hardcoded rt-signal, but also
>> searches for an unused one.
>>>
>>> So perhaps the "search for unused rt-signal" should be exposed as a
>> generic support function for the application (and this driver) to use.
>>
>> There is no safe way to use a signal deep inside DPDK in a driver.
>>
>> This is not the kind of thing that should be exposed to the
>> application.
>>
>> The algorithm for finding an RT signal conforms to the recommended
>> policy on the signal(7)
>> manual page.
>>
>>        programs should never refer to real-time signals using hard-
>>        coded numbers, but instead should always refer to real-time
>> signals
>>        using the notation SIGRTMIN+n, and include suitable (run-time)
>> checks
>>        that SIGRTMIN+n does not exceed SIGRTMAX.
>>
>> The application should be following the proscribed policy on the man
>> page.
>> If it doesn't it is broken.
> 
> Great. That fully addresses my concern.
> 
> Acked-by: Morten Brørup <mb@smartsharesystems.com>
> 

Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>