[PATCH v3 26/54] dyndbg: change __dynamic_func_call_cls* macros into expressions

[jim.cromie at gmail.com]

On Tue, Apr 15, 2025 at 4:06 AM Louis Chauvet <louis.chauvet at bootlin.com> wrote:
>
>
>
> Le 02/04/2025 à 19:41, Jim Cromie a écrit :
> > The Xe driver's XE_IOCTL_DBG macro calls drm_dbg() from inside an if
> > (expression).  This breaks when CONFIG_DRM_USE_DYNAMIC_DEBUG=y because
> > the invoked macro has a do-while-0 wrapper.
> >
> >     if (cond && (drm_dbg("expr-form"),1)) {
> >        ... do some more stuff
> >     }
> >
> > Fix for this usage by changing __dynamic_func_call_cls{,_no_desc}
> > macros into expressions, by replacing the do-while-0s with a ({ })
> > wrapper.  In the common usage, the trailing ';' converts the
> > expression into a statement.
> >
> >     drm_dbg("statement form");
> >
> > Signed-off-by: Jim Cromie <jim.cromie at gmail.com>
> > ---
> > ---
> >   include/linux/dynamic_debug.h | 12 ++++++------
> >   1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
> > index ce221a702f84..2d87cca27544 100644
> > --- a/include/linux/dynamic_debug.h
> > +++ b/include/linux/dynamic_debug.h
> > @@ -337,20 +337,20 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
> >    * (|_cls): adds in _DPRINT_CLASS_DFLT as needed
> >    * (|_no_desc):     former gets callsite descriptor as 1st arg (for prdbgs)
> >    */
> > -#define __dynamic_func_call_cls(id, cls, fmt, func, ...) do {        \
> > -     DEFINE_DYNAMIC_DEBUG_METADATA_CLS((id), cls, fmt);      \
> > +#define __dynamic_func_call_cls(id, cls, fmt, func, ...) ({  \
> > +     DEFINE_DYNAMIC_DEBUG_METADATA_CLS(id, cls, fmt);        \
>
> You remove the protection around id here.
>
> >       if (DYNAMIC_DEBUG_BRANCH(id))                           \
> > -             func(&id, ##__VA_ARGS__);                       \
> > -} while (0)
> > +             func(&(id), ##__VA_ARGS__);                     \
>
> But you add the protection here.
>
> I think in macro it is better to be defensive, so I expect to have ()
> everywhere (except places where it breaks the compilation).
>

yeah, Im a bit inconsistent.
defensive parens are almost never a compilation err.
I'll go thru the macros again


> > +})
> >   #define __dynamic_func_call(id, fmt, func, ...)                             \
> >       __dynamic_func_call_cls(id, _DPRINTK_CLASS_DFLT, fmt,           \
> >                               func, ##__VA_ARGS__)
> >
> > -#define __dynamic_func_call_cls_no_desc(id, cls, fmt, func, ...) do {        \
> > +#define __dynamic_func_call_cls_no_desc(id, cls, fmt, func, ...) ({  \
> >       DEFINE_DYNAMIC_DEBUG_METADATA_CLS(id, cls, fmt);                \
> >       if (DYNAMIC_DEBUG_BRANCH(id))                                   \
> >               func(__VA_ARGS__);                                      \
> > -} while (0)
> > +})
> >   #define __dynamic_func_call_no_desc(id, fmt, func, ...)                     \
> >       __dynamic_func_call_cls_no_desc(id, _DPRINTK_CLASS_DFLT,        \
> >                                       fmt, func, ##__VA_ARGS__)
>
> --
> Louis Chauvet, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
>
>