Keith Owens wrote:
> Change every module that registers anything to make sure that they
> replace the register data with stubs on exit? And make sure that all
> of them do so before they sleep anywhere in module cleanup? It would
> work but is it the best solution?
Not when you put it that way.
> The existing method of avoiding module races is beginning to look like
> a dead dog. Look at the constraints we have to run under :-
> * All code that can ever call any module functions must either have a
> reference count on that module or must run under the same lock as the
> module unload (big kernel lock).
> * Every module must be checked to see that it never sleeps before doing
> * Every module must be checked to see that it never sleeps after doing
These two can be avoided by hoisting the inc/dec up into the netdevice
layer. But we need to wrap dev->get_stats(), dev->ioctl(), etc with
inc/dec as well..
> * Every module that registers anything must change the registered
> functions in module cleanup and must do so before sleeping (new).
> That is an awful lot of opportunities to make mistakes. And forcing
> lots of code to run under the big kernel lock does not scale well.
I am now remembering Alexey's disparaging comments about "self-modifying
It sucks and I'm still seeking a single, centralised fix. How about plan
J (warning: inelegance approaching):
Module unload is a very rare occurence, so let's penalise that and that
We grab the ENTIRE machine within sys_delete_module.
Like, grab the big kernel lock, then wait until ALL other CPUs are
spinning on the kernel lock, and then allow sys_delete_module to