From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt 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 Message-ID: <20180121170140.23d1ff12@gandalf.local.home> References: <20180121143117.19805-1-wsa+renesas@sang-engineering.com> <20180121143117.19805-2-wsa+renesas@sang-engineering.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <20180121143117.19805-2-wsa+renesas@sang-engineering.com> Sender: linux-renesas-soc-owner@vger.kernel.org To: Wolfram Sang Cc: devicetree@vger.kernel.org, Tyrel Datwyler , Geert Uytterhoeven , linux-renesas-soc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Rob Herring , Frank Rowand , linux-kernel@vger.kernel.org List-Id: devicetree@vger.kernel.org On Sun, 21 Jan 2018 15:31:17 +0100 Wolfram Sang wrote: > From: Tyrel Datwyler > > 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 > [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 >>From the tracing perspective: Reviewed-by: Steven Rostedt (VMware) -- Steve > ---