Re: [dpdk-dev] [dpdk-dev, 1/3] rte_interrupts: add rte_eal_intr_exit to shut down IRQ thread

["Liang, Cunming" <cunming.liang@intel.com>]

Hi Mattew,

Thank you for your time.

On 3/22/2016 3:39 PM, Matthew Hall wrote:
> On Mon, Mar 21, 2016 at 03:58:44PM +0800, Liang, Cunming wrote:
>> the default termination handler
> I am not so experienced with this "default termination handler". Can someone
> clarify what it is so I could comment better about it?
For example, you're handling SIGINT. After finishing your necessary app 
cleanup, then 'signal(SIGINT, SIG_DFL); raise(SIGINT);'.
The default signal handler can terminate the interrupt thread.

>
>> If EINTR is caused by some non-term purpose signals, are you going
>> to exit the interrupt thread any way?
> We should discuss what makes sense here. I'm just trying to get some things
> working and finding EINTR was getting eaten and causing infinite looping.
SIGINT/SIGTERM causes EINTR return, while SIGUSR1 also can cause the 
EINTR return. For the dedicated EAL interrupt thread, it won't be 
expected to exit for all kinds of the cause.
On this view, I'm in favor of your patch which cancel the interrupt 
thread, but don't directly return by the EINTR.

>
>> Without setting 'PTHREAD_CREATE_DETACHED' won't cause the infinite
>> loop. However by using pthread_cancel to terminate the thread,
>> indeed it's necessary to set 'PTHREAD_CREATE_DETACHED'.
> My general understanding is that PTHREAD_CREATE_DETACHED should be used for
> any thread, which should not keep a process open by itself if it is executing,
> i.e. a "daemon thread". I believe the interrupt thread qualifies as such a
> thread if I have understood everything right (which is hard to promise when
> you only work in DPDK in spare time).
>
>> It looks like 'pthread_cancel' is the right way and I saw it
>> continue keeps current EINTR handling in EAL interrupt thread.
> It is one option. Depending what makes the most sense.
>
>> 1. Can you explain and add patch comments why default signal handler
>> is not good enough to terminate app.
> Yes if someone call tell me more about what it is so I can check it.
>
>> 2. I propose to add addition comments on rte_epoll_wait() API
>> description. For any signal, it causes an error return, user needs
>> to handle.
> Agreed.
>
>> 3. Will you do a favorite to add 'PTHREAD_CREATE_DETACHED' to all
>> EAL pthread too.
> As a spare time developer I am a bit conservative about too large of a scope
> and messing with code for other threads or features I didn't personally use or
> test. This is because I don't have the same QA resources as Intel / 6WIND /
> etc.. Some help from a full time developer would be great here.
All right, reasonable to me.

>
>> Cunming
> Matthew.