Re: [dpdk-dev] [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup

From: Maxime Coquelin

On 1/14/21 2:09 PM, Matan Azrad wrote:

quoted

From: Maxime Coquelin

quoted

Hi Matan,

On 1/14/21 12:49 PM, Matan Azrad wrote:

quoted

Hi Maxime and David

Thank you for Review.

From: David Marchand

quoted

On Fri, Jan 8, 2021 at 9:48 AM David Marchand
[off-list ref] wrote:

quoted

quoted

I wonder if it would be possible and cleaner to disable
cancellation on the thread while the mutex is held?

Yes, we can cause thread to return by some global variable sync.
It is the same logic.

No, that was not my suggestion. My suggestion is to block the thread
cancellation while in the critical section, using pthread_setcancelstate().

Yes, Generally it is better to let the thread control his cancellation, either

cancel itself or enabling\disabling cancellations.

quoted

I don't see a reason to wait for the thread in current logic - the critical section

is not important to be completed here.

The reason I see is there are quite a few things done in this critical section. And
if tomorrow someone add new things in it, he may not know the thread can be
cancelled at any time, which could cause hard to debug issues.

As I said, here it is not needed, this thread designed just to cause guest notifications.

The optional future developer mistake can be done also outside the critical section in in any other place - we cannot protect it.

The design choice is to close the thread fast.

quoted

We just want to close the thread and to clean the mutex.

quoted

quoted

quoted

quoted

+1

IEEE Std 1003.1-2001/Cor 2-2004, item XBD/TC2/D6/26 is applied,
adding pthread_t to the list of types that are not required to be
arithmetic types, thus allowing pthread_t to be defined as a structure.

It would be better to leave pthread_t alone and not interpret it:

if (priv->timer_tid) {
    pthread_cancel(priv->timer_tid);
    pthread_join(priv->timer_tid, &status); }
priv->timer_tid = 0;

I'm not sure why you think it is better in this specific case.
The cancellation will close the thread in faster way, no need to
wait for the

thread to close itself.

quoted

quoted

--
David Marchand