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From: Olivier Matz <olivier.matz@6wind.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: dev@dpdk.org, David Marchand <david.marchand@redhat.com>,
	Thomas Monjalon <thomas@monjalon.net>
Subject: Re: [dpdk-dev] [PATCH] net/pcap: fix registration of timestamp dynamic field
Date: Fri, 13 Nov 2020 21:35:34 +0100
Message-ID: <20201113203534.GB6890@arsenic.home> (raw)
In-Reply-To: <e5e25f86-ce2f-bbe5-6292-47473c585705@intel.com>

On Fri, Nov 13, 2020 at 02:02:38PM +0000, Ferruh Yigit wrote:
> On 11/13/2020 1:13 PM, Olivier Matz wrote:
> > On Fri, Nov 13, 2020 at 11:39:57AM +0100, Olivier Matz wrote:
> > > In pcap pmd, the timestamp mbuf dynamic field is mandatory. When the
> > > pcap pmd is created in a secondary process (this is the case for pdump),
> > > it cannot be registered because this is not allowed from a secondary
> > > process.
> > > 
> > > To ensure that the field is properly registered, do it from probe()
> > > instead of configure(). Indeed, probe() is invoked on the primary
> > > process when a device is created in a secondary.
> > > 
> 
> probe() invoked first in the primary, later in the secondary, both process
> calls the driver probe(). But for this case probe(), and dynfield register,
> being called first in primary seems solving the problem.
> Would you be OK to change last sentences as:
> "Indeed, probe() is first invoked on the primary process when a device is
> created in a secondary, this enables registering dynfield from secondary
> process."

Yes, it is more precise, thanks

> > > Bugzilla ID: 571
> > > Fixes: d23d73d088c1 ("net/pcap: switch Rx timestamp to dynamic mbuf field")
> > > 
> > > Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> 
> Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
> 
> > > ---
> > 
> > One additional comment about this patch.
> > 
> > While it solves the issue described in the bug report, there may still
> > be a gap when it is needed to register a dynamic field/flag from a
> > secondary process. This happens when registering and configuring devices
> > from a secondary process (is it supported?). It happens if the secondary
> > process initializes a library which is not initialized in primary, and
> > which requires a dynamic field.
> > 
> >  From afar, it does not look too difficult to implement dynamic field
> > registration from secondary processes. The only thing missing is a way
> > to allocate the shared memory in the primary process at initialization.
> > Currently, there is no init callback that is invoked when eal init is
> > done.
> > 
> 
> I was checking this, it seems what prevents to register dnyfield from the
> secondary process is 'init_shared_mem()', so if primary process registers
> any dynfield first, secondary process can register dynfields too.
> Do you think should this limitation documented?

Currently, registration from secondary is explicitly denied, with a code
like this:

	if (rte_eal_process_type() != RTE_PROC_PRIMARY) {
		rte_errno = EPERM;
		return -1;
	}

> > This is the exact same problem than for this issue:
> > http://inbox.dpdk.org/dev/20200504074227.GA6327@platinum/#t
> > 
> 
> <...>
> 

      parent reply	other threads:[~2020-11-13 20:35 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-13 10:39 Olivier Matz
2020-11-13 13:13 ` Olivier Matz
2020-11-13 14:02   ` Ferruh Yigit
2020-11-13 17:23     ` Ferruh Yigit
2020-11-13 20:35     ` Olivier Matz [this message]

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