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From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: Thomas Monjalon <thomas.monjalon@6wind.com>,
	Hiroyuki Mikita <h.mikita89@gmail.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>
Subject: Re: [dpdk-dev] [PATCH v2] mbuf: decrease refcnt when detaching
Date: Tue, 17 May 2016 12:59:46 +0000	[thread overview]
Message-ID: <2601191342CEEE43887BDE71AB97725836B518A4@irsmsx105.ger.corp.intel.com> (raw)
In-Reply-To: <2164081.rUYNJaTDcf@xps13>


Hi Thomas,
 
> > The rte_pktmbuf_detach() function should decrease refcnt on a direct
> > buffer.
> >
> > Signed-off-by: Hiroyuki Mikita <h.mikita89@gmail.com>
> > ---
> > v2:
> > * introduced a new function rte_pktmbuf_detach2() which decrease refcnt.
> 
> As you have noticed, "whenever the indirect buffer is detached,
> the reference counter on the direct buffer is decremented."
> So the current behaviour of rte_pktmbuf_detach() is buggy.
> Why not fix it without renaming?
> If you consider this behavioral bug is part of the API, we
> can fix it in a new function unattach and deprecate detach.
> But Konstantin, why do you want to keep a restore function?
> What is the need?

I think it might be a useful functionality in some situations:
some users can attach/detach to external memory buffers (no mbufs)
and similar functionality is required.
Let say right now examples/vhost/main.c has its own pktmbuf_detach_zcp()
which is doing pretty much the same - restore original values, after detaching
mbuf from external (virtio) memory buffer.
Would be good if we'll use a standard API function here.
Konstantin  

> 
> Please explicit the function name for the detach operation in
> doc/guides/prog_guide/mbuf_lib.rst (whatever detach2 or unattach).
> 
> > * marked rte_pktmbuf_detach() as deprecated.
> > * added comments about refcnt to rte_pktmbuf_attach() and rte_pktmbuf_detach().
> > * checked refcnt when detaching in unit tests.
> > * added this issue to release notes.

  reply	other threads:[~2016-05-17 12:59 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-15 15:50 [dpdk-dev] [PATCH] " Hiroyuki Mikita
2016-05-16  0:05 ` Ananyev, Konstantin
2016-05-16  2:46   ` Hiroyuki MIKITA
2016-05-16  8:49     ` Ananyev, Konstantin
2016-05-16  9:13     ` Thomas Monjalon
2016-05-16 16:24       ` Hiroyuki MIKITA
2016-05-16  8:52 ` Olivier Matz
2016-05-16 16:53 ` [dpdk-dev] [PATCH v2] " Hiroyuki Mikita
2016-05-17 10:58   ` Bruce Richardson
2016-05-17 11:06   ` Ananyev, Konstantin
2016-05-17 12:43   ` Thomas Monjalon
2016-05-17 12:59     ` Ananyev, Konstantin [this message]
2016-05-17 13:39       ` Thomas Monjalon
2016-05-17 13:44         ` Ananyev, Konstantin
2016-05-17 14:19           ` Thomas Monjalon
2016-05-17 15:45             ` Ananyev, Konstantin
2016-05-17 16:12               ` Hiroyuki MIKITA
2016-05-17 16:35   ` [dpdk-dev] [PATCH v3] " Hiroyuki Mikita
2016-05-18 11:58     ` Olivier Matz
2016-05-18 14:29       ` Hiroyuki Mikita
2016-05-18 14:41     ` [dpdk-dev] [PATCH v4] " Hiroyuki Mikita
2016-05-18 15:51       ` Olivier Matz
2016-05-19 12:38         ` Thomas Monjalon

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