Re: [Ksummit-discuss] Self nomination

[Dan Williams <dan.j.williams@intel.com>]

On Fri, Jul 31, 2015 at 11:22 AM, Greg KH <greg@kroah.com> wrote:
> On Fri, Jul 31, 2015 at 02:17:58PM -0400, Dave Jones wrote:
>> On Fri, Jul 31, 2015 at 11:12:45AM -0700, Greg Kroah-Hartman wrote:
>>  > On Fri, Jul 31, 2015 at 12:51:53PM -0500, Bjorn Helgaas wrote:
>>  > > I prefer that a dmesg collected in the simplest possible way, with no
>>  > > special config or boot flags, be as useful as possible.  So converting
>>  > > to dynamic debug requires much more thought about which messages
>>  > > should be always printed and which should become dynamic.
>>  >
>>  > Why would a debugging message ever not be dynamic?  They are there for
>>  > you to use, and turn off when you are done.  If you want a user to
>>  > report the output of them, then of course they should be dynamic so they
>>  > can just write a line to a debugfs file and then start seeing them
>>
>> This implies a user knows ahead of time what bugs they are going to hit,
>> and which messages they need to enable.  For hard-to-reproduce bugs,
>> or bugs that exhibit non-obvious symptoms, this isn't workable.
>
> Fair enough, but wouldn't those messages be "errors"?
>
> Anyway, this is way off-topic from the original thread, it all comes
> down to specifics of the message that is being written and the
> surrounding issues of why it would be written.

One more thought on this tangent... I've had a task stuck at the
bottom of my backlog to look at extending dynamic_debug call sites to
optionally be tracepoints so that you could feasibly have debug on all
the time with less run time impact.