Messages in this thread | | | From | Łukasz Bartosik <> | Date | Mon, 2 Oct 2023 12:07:41 +0200 | Subject | Re: [PATCH v1] dynamic_debug: add support for logs destination |
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pon., 18 wrz 2023 o 09:20 Łukasz Bartosik <lb@semihalf.com> napisał(a): > > pt., 15 wrz 2023 o 20:02 <jim.cromie@gmail.com> napisał(a): > > > > On Fri, Sep 15, 2023 at 9:49 AM Łukasz Bartosik <lb@semihalf.com> wrote: > > > > > > Add support for selection of dynamic debug logs destination. > > > When enabled it allows to configure destination of each callsite > > > individually. The option adds a framework (described by struct > > > ddebug_dst_ops) which provides flexible means to add a new destination > > > for debug logs. On top of the framework support for trace instance as > > > destination is added. By default destination of debug logs is syslog. > > > Syslog can be set explicitly by using dst keyword or is selected by > > > default when dst keyword is omitted, for example: > > > > A while back, > > Cc: Vincent Whitchurch <vincent.whitchurch@axis.com> > > proposed these patches: > > https://lore.kernel.org/lkml/20200825153338.17061-1-vincent.whitchurch@axis.com/ > > > > his approach adds a single flag, +x or (my pref) +T > > which sends the pr_debug to tracefs, independent of +p. > > Steve Rostedt offered feedback on one of the versions, > > and one could read that as provisional acceptance. > > > > Ive worked his patchset since, it is here: > > https://github.com/jimc/linux/tree/dd-trc-11 > > (it has some unrelated bits too) > > > > but it sits atop another patchset: > > https://lore.kernel.org/lkml/20230911230838.14461-1-jim.cromie@gmail.com/ > > or for git remote add > > https://github.com/jimc/linux/tree/dd-fix-5i > > > > I looked through the patches you pointed me to. The solution with > +T/+x is elegant and tailored to specific needs. > Our rationale to write pr_debug/dev_dbg logs to tracefs is similar to > Vincent's to aid us in debugging. > Unfortunately the solution with +T/+x does not cover our use case. > > Our use case is different. We experience issues reported by Chromebook > users which are difficult to reproduce > that's why we would like to enable debug logs to be written to tracefs > on productions systems. > When users experiences an issues and sends us a feedback report the > debug logs written to tracefs would be > attached to the feedback report. We would like to write debug logs to > a separate trace instances based on > the subsystem/driver. Our initial areas of interest/issues are usbcore > and thunderbolt drivers/subsystems. > More may come in the future. > > With my proposal this could be achieved for the thunderbolt subsystem > with the following steps: > * enable kernel configuration option CONFIG_DYNAMIC_DEBUG_CORE, > * enable kernel configuration option DYNAMIC_DEBUG_DST and set its > operation mode to Static. > * add the option to the thunderbolt's drivers/thunderbolt/Makefile > in order to compile in debug logs: > CFLAGS_nhi.o := -DDYNAMIC_DEBUG_MODULE > * compile the kernel and update it on a target device, > * finally append the entry to the kernel boot command line: > thunderbolt.dyndbg="dst trace:thunderbolt =p" > > Both the solutions (I mean +x/+T and mine proposal) have pros and cons. > Maybe both could coexist together, +x/+T by default and this patch as > configurable option > which adds more flexibility ? >
Jim,
Do you have thoughts/comments about/to my proposal ?
Thanks, Lukasz
> > > > syslog and/or tracefs seems sufficient, do you have a 3rd destination ? > > > > I don't have a use case for the third destination, but for example > adding socket destination to my proposal would be relatively fast and > easy (that would be for limited use only after a network is up and > running). > > Thanks, > Lukasz > > > thanks
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