[PATCH 1/1] ring: safe partial ordering for head/tail update

[Ola Liljedahl]

> On 2025-09-24, 09:50, "Konstantin Ananyev" <konstantin.ananyev at huawei.com <mailto:konstantin.ananyev at huawei.com>> wrote:
> > Sure, I am talking about MT scenario.
> > I think I already provided an example: DPDK mempool library (see below).
> > In brief, It works like that:
> > At init it allocates ring of N memory buffers and ring big enough to hold all of them.
>
> Sorry, I meant to say: "it allocates N memory buffers and ring big enough to hold all of them".
>
> > Then it enqueues all allocated memory buffers into the ring.
> > mempool_get - retrieves (dequeues) buffers from the ring.
> > mempool_put - puts them back (enqueues) to the ring
> > get() might fail (ENOMEM), while put is expected to always succeed.
But how does the thread which calls mempool_put() get hold of the memory buffers that
were obtained using mempool_get() by some other thread? Or this is not the scenario you
are worrying about?
Is it rather that multiple threads independently call mempool_get() and then mempool_put()
on their own buffers? And you are worried that a thread will fail to return (mempool_put) a
buffer that it earlier allocated (mempool_get)? We could create a litmus test for that.

- Ola


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