On Fri, Mar 19, 2021 at 02:31:19PM +0100, Rasmus Villemoes wrote: > On 18/03/2021 12.31, Peter Zijlstra wrote: > > The intent is to avoid writing init code after init (because the text > > might have been freed). The code is needlessly different between > > jump_label and static_call and not obviously correct. > > > > The existing code relies on the fact that the module loader clears the > > init layout, such that within_module_init() always fails, while > > jump_label relies on the module state which is more obvious and > > matches the kernel logic. > > > > Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> > > --- > > kernel/static_call.c | 14 ++++---------- > > 1 file changed, 4 insertions(+), 10 deletions(-) > > > > --- a/kernel/static_call.c > > +++ b/kernel/static_call.c > > @@ -149,6 +149,7 @@ void __static_call_update(struct static_ > > }; > > > > for (site_mod = &first; site_mod; site_mod = site_mod->next) { > > + bool init = system_state < SYSTEM_RUNNING; > > I recently had occasion to look at whether that would be a suitable > condition for knowing whether __init stuff was gone, but concluded that > it's not. Maybe I'm wrong. init/main.c:
Ha, me too: https://lkml.kernel.org/r/YFMToXI/3qjlm...@hirez.programming.kicks-ass.net and I share your concern. > Dunno, probably overkill, but perhaps we could have an atomic_t (or > refcount, whatever) init_ref inited to 1, with init_ref_get() doing an > inc_unless_zero, and iff you get a ref, you're free to call (/patch) > __init functions and access __initdata, but must do init_ref_put(), with > PID1 dropping its initial ref and waiting for it to drop to 0 before > doing the *free_initmem() calls. I'd as soon simply add another SYSTEM state. That way we don't have to worry about who else looks at RUNNING for what etc..