From: Steven Rostedt <rostedt@goodmis.org>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: devicetree@vger.kernel.org,
Tyrel Datwyler <tyreld@linux.vnet.ibm.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
linux-renesas-soc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Rob Herring <robh+dt@kernel.org>,
Frank Rowand <frowand.list@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 1/1] of: introduce event tracepoints for dynamic device_node lifecyle
Date: Sun, 21 Jan 2018 17:01:40 -0500 [thread overview]
Message-ID: <20180121170140.23d1ff12@gandalf.local.home> (raw)
In-Reply-To: <20180121143117.19805-2-wsa+renesas@sang-engineering.com>
On Sun, 21 Jan 2018 15:31:17 +0100
Wolfram Sang <wsa+renesas@sang-engineering.com> wrote:
> From: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
>
> 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.
>
> Further, when pseries lpars are migrated to a different machine we
> perform a live update of our device tree to bring it into alignment with
> the configuration of the new machine. The of_reconfig_notify trace point
> provides a mechanism that can be turned for debuging the device tree
> modifications with out having to build a custom kernel to get at the
> DEBUG code introduced by commit 00aa37206e1a54 ("of/reconfig: Add debug
> output for OF_RECONFIG notifiers").
>
> The following trace events are provided: of_node_get, of_node_put,
> of_node_release, and of_reconfig_notify. These trace points require a
> kernel built with ftrace support to be enabled. In a typical environment
> where debugfs is mounted at /sys/kernel/debug the entire set of
> tracepoints can be set with the following:
>
> echo "of:*" > /sys/kernel/debug/tracing/set_event
>
> or
>
> echo 1 > /sys/kernel/debug/tracing/events/of/enable
>
> The following shows the trace point data from a DLPAR remove of a cpu
> from a pseries lpar:
>
> cat /sys/kernel/debug/tracing/trace | grep "POWER8@10"
>
> cpuhp/23-147 [023] .... 128.324827:
> of_node_put: refcount=5, dn->full_name=/cpus/PowerPC,POWER8@10
> cpuhp/23-147 [023] .... 128.324829:
> of_node_put: refcount=4, dn->full_name=/cpus/PowerPC,POWER8@10
> cpuhp/23-147 [023] .... 128.324829:
> of_node_put: refcount=3, dn->full_name=/cpus/PowerPC,POWER8@10
> cpuhp/23-147 [023] .... 128.324831:
> of_node_put: refcount=2, dn->full_name=/cpus/PowerPC,POWER8@10
> drmgr-7284 [009] .... 128.439000:
> of_node_put: refcount=1, dn->full_name=/cpus/PowerPC,POWER8@10
> drmgr-7284 [009] .... 128.439002:
> of_reconfig_notify: action=DETACH_NODE, dn->full_name=/cpus/PowerPC,POWER8@10,
> prop->name=null, old_prop->name=null
> drmgr-7284 [009] .... 128.439015:
> of_node_put: refcount=0, dn->full_name=/cpus/PowerPC,POWER8@10
> drmgr-7284 [009] .... 128.439016:
> of_node_release: dn->full_name=/cpus/PowerPC,POWER8@10, dn->_flags=4
>
> Signed-off-by: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
> [wsa: fixed commit abbrev and one of the sysfs paths in commit desc,
> removed trailing space and fixed pointer declaration in code]
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
>From the tracing perspective:
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
-- Steve
> ---
next prev parent reply other threads:[~2018-01-21 22:01 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-21 14:31 [RFC PATCH v2 0/1] of: easier debugging for node life cycle issues Wolfram Sang
2018-01-21 14:31 ` [RFC PATCH v2 1/1] of: introduce event tracepoints for dynamic device_node lifecyle Wolfram Sang
2018-01-21 22:01 ` Steven Rostedt [this message]
2018-01-25 6:48 ` Frank Rowand
2018-01-25 6:58 ` Frank Rowand
[not found] ` <4cc627c4-1aaf-b8d5-5a26-eea7e596743f-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-01-25 8:01 ` Geert Uytterhoeven
2018-01-25 22:40 ` Tyrel Datwyler
[not found] ` <25f83d0d-bc67-f1b5-cadb-838987fd846d-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2018-01-25 23:31 ` Frank Rowand
2018-01-25 8:32 ` Frank Rowand
2018-01-22 8:43 ` [RFC PATCH v2 0/1] of: easier debugging for node life cycle issues Frank Rowand
2018-01-22 11:49 ` Wolfram Sang
2018-01-23 12:11 ` Michael Ellerman
2018-01-23 19:53 ` Frank Rowand
2018-01-25 6:47 ` Frank Rowand
[not found] ` <11cf8fac-d2fe-ecdb-546f-de3c3b42a637-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-01-25 23:12 ` Wolfram Sang
2018-01-26 0:42 ` Frank Rowand
2018-01-25 6:48 ` Frank Rowand
[not found] ` <20180121143117.19805-1-wsa+renesas-jBu1N2QxHDJrcw3mvpCnnVaTQe2KTcn/@public.gmane.org>
2018-01-25 6:55 ` Frank Rowand
2018-01-25 11:03 ` Steven Rostedt
2018-01-25 21:49 ` Frank Rowand
[not found] ` <a30d4cd3-0068-8cca-cc2f-ca207d0d278b-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-01-25 23:14 ` Wolfram Sang
2018-01-26 0:46 ` Frank Rowand
2018-02-01 17:10 ` Steven Rostedt
2018-01-25 23:53 ` Tyrel Datwyler
2018-01-26 1:08 ` Frank Rowand
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