From: "Oliver O'Halloran" <oohall@gmail.com>
To: Rob Herring <robh+dt@kernel.org>
Cc: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Frank Rowand <frowand.list@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
rostedt@goodmis.org, Ingo Molnar <mingo@redhat.com>,
Nathan Fontenot <nfont@linux.vnet.ibm.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH] of: introduce event tracepoints for dynamic device_node lifecyle
Date: Wed, 19 Apr 2017 12:30:50 +1000 [thread overview]
Message-ID: <CAOSf1CH8HgP0rKd0WCp87BADYcEGT5OCoq_yq+f3ZeoyTcXeng@mail.gmail.com> (raw)
In-Reply-To: <CAL_Jsq+GRkssqcn0wGzMgQRUtT-BO4zNDyYE7u1Cr5EhADK1SQ@mail.gmail.com>
On Wed, Apr 19, 2017 at 2:46 AM, Rob Herring <robh+dt@kernel.org> wrote:
> On Mon, Apr 17, 2017 at 7:32 PM, Tyrel Datwyler
> <tyreld@linux.vnet.ibm.com> wrote:
>> This patch introduces event tracepoints for tracking a device_nodes
>> reference cycle as well as reconfig notifications generated in response
>> to node/property manipulations.
>>
>> With the recent upstreaming of the refcount API several device_node
>> underflows and leaks have come to my attention in the pseries (DLPAR) dynamic
>> logical partitioning code (ie. POWER speak for hotplugging virtual and physcial
>> resources at runtime such as cpus or IOAs). These tracepoints provide a
>> easy and quick mechanism for validating the reference counting of
>> device_nodes during their lifetime.
>
> Not really relevant for this patch, but since you are looking at
> pseries and refcounting, the refcounting largely exists for pseries.
> It's also hard to get right as this type of fix is fairly common. It's
> now used for overlays, but we really probably only need to refcount
> the overlays or changesets as a whole, not at a node level. If you
> have any thoughts on how a different model of refcounting could work
> for pseries, I'd like to discuss it.
One idea I've been kicking around is differentiating short and long
term references to a node. I figure most leaks are due to a missing
of_node_put() within a stack frame so it might be possible to use the
ftrace infrastructure to detect and emit warnings if a short term
reference is leaked. Long term references are slightly harder to deal
with, but they're less common so we can add more detailed reference
tracking there (devm_of_get_node?).
Oliver
next prev parent reply other threads:[~2017-04-19 2:30 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-18 0:32 [PATCH] of: introduce event tracepoints for dynamic device_node lifecyle Tyrel Datwyler
2017-04-18 0:35 ` Tyrel Datwyler
2017-04-18 16:46 ` Rob Herring
2017-04-19 2:30 ` Oliver O'Halloran [this message]
2017-04-19 10:13 ` Michael Ellerman
2017-04-19 21:13 ` Tyrel Datwyler
2017-04-19 0:07 ` Frank Rowand
2017-04-19 1:31 ` Michael Ellerman
2017-04-19 2:31 ` Frank Rowand
2017-04-19 18:33 ` Tyrel Datwyler
2017-04-19 23:27 ` Tyrel Datwyler
2017-04-20 2:33 ` Steven Rostedt
2017-04-20 4:47 ` Frank Rowand
2017-04-20 5:24 ` Tyrel Datwyler
2017-04-20 13:37 ` Steven Rostedt
2017-04-20 4:43 ` Frank Rowand
2017-04-20 5:13 ` Frank Rowand
2017-04-20 16:51 ` Tyrel Datwyler
2017-04-20 19:34 ` Frank Rowand
2017-04-21 1:57 ` Michael Ellerman
2017-04-19 1:42 ` Frank Rowand
2017-04-19 2:49 ` Steven Rostedt
2017-04-19 18:45 ` Tyrel Datwyler
2017-04-20 2:37 ` Frank Rowand
2017-04-20 10:44 ` Frank Rowand
2017-04-19 2:46 ` Steven Rostedt
2017-04-19 3:12 ` Frank Rowand
2017-04-19 17:44 ` Frank Rowand
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