Re: [PATCH v2 03/15] drivers: thermal: tsens: Add __func__ identifier to debug statements
From: Amit Kucheria
Date: Thu Aug 29 2019 - 12:14:18 EST
On Thu, Aug 29, 2019 at 8:49 PM Daniel Thompson
> On Thu, Aug 29, 2019 at 07:58:45PM +0530, Amit Kucheria wrote:
> > On Thu, Aug 29, 2019 at 7:35 PM Daniel Thompson
> > <daniel.thompson@xxxxxxxxxx> wrote:
> > >
> > > On Tue, Aug 27, 2019 at 05:43:59PM +0530, Amit Kucheria wrote:
> > > > Printing the function name when enabling debugging makes logs easier to
> > > > read.
> > > >
> > > > Signed-off-by: Amit Kucheria <amit.kucheria@xxxxxxxxxx>
> > > > Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
> > > > Reviewed-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> > >
> > > This should need to be manually added at each call site; it is already
> > > built into the logging system (the f flag for dynamic debug)?
> > I assume you meant "shouldn't".
> Quite so. Sorry about that.
> > I haven't yet integrated dynamic debug into my daily workflow.
> > Last time I looked at it, it was a bit bothersome to use because I
> > needed to lookup exact line numbers to trigger useful information. And
> > those line numbers constantly keep changing as I work on the driver,
> > so it was a bit painful to script. Not to mention the syntax to frob
> > the correct files in debugfs to enable this functionality.
> > As opposed to this, adding the following to the makefile is so easy. :-)
> > CFLAGS_tsens-common.o := -DDEBUG
> > Perhaps I am using it all wrong? How would I go about using dynamic
> > debug instead of this patch?
> Throwing dyndbg="file <fname>.c +pf" onto the kernel command line is a
> good start (+p enables debug level prints, +f causes messages to include
> the function name).
That's useful to know.
$ git grep __func__ | wc -l
Want to send some patches? :-)
> When the C files map to module names (whether the modules are actually
> built-in or not) then <module>.dyndbg=+pf is a bit cleaner and allows
> you to debug the whole of a driver without how it is decomposed into
And if changing the kernel cmdline options isn't possible or is inconvenient?
> There are (many) other controls to play with but the above should be
> sufficient to simulate -DDEBUG .
The "hard" bit is explicitly poking the line number in a file to
activate a paricular pr_dbg statement. Even if I scripted it, those
lines numbers keep changing in an actively developed driver.
Somehow, I've always felt dyndbg was more useful to debug a production
system where recompiling the kernel wasn't an option e.g. reporting an
issue back to a distro-kernel vendor.