On Sun, May 21, 2017 at 07:57:53PM +0200, Thomas Gleixner wrote:

On Thu, 18 May 2017, Christoph Hellwig wrote:

quoted

On Thu, May 18, 2017 at 10:24:48AM +0200, Christoph Hellwig wrote:

quoted

quoted

b) give the union a name (breaks any reference to timer_list->func in C code):

 +       union {
 +               void            (*func)(struct timer_list *timer);
 +               void            (*function)(unsigned long);
 +       } u;

I'll look into that, as it seems a lot safer, and places outside
the timer code shouldn't really touch it (although I bet they do,
so more fixes for this series..)

Meh.  All the old init_timer users set function directly, so
I guess we need to use the other approach.

There is another possibility. Create a coccinelle script which wraps all

      timer.function = f;
      timer->function = f;

assignements into a helper timer_set_function(timer, func) and ask Linus to
run it right before the next -rc. That handles everything in tree and the
few new instances in next can be addressed with patches sent to the
maintainers.

FWIW, there was another possible approach - I toyed with that several years
ago, but it didn't go anywhere.  Namely, make timer.function take void *
*and* turn the setup part into setup(timer, callback, argument), verifying
that
	* callback(argument) will be acceptable expression for C typechecking
	* callback returns void
	* argument is a pointer type
then cast callback to void (*)(void *) and argument to void *.  That way
we get rid of any boilerplate in callbacks and get sane typechecking...