Re: alpha fp-emu vs module refcounting

Ivan Kokshaysky
2004-05-07T22:37:50Z

On Fri, May 07, 2004 at 04:35:12PM +0200, Christoph Hellwig wrote:
> On Fri, May 07, 2004 at 06:32:08PM +0400, Ivan Kokshaysky wrote:
> > - MOD_INC_USE_COUNT;
> > + BUG_ON(!try_module_get(THIS_MODULE));
>
> This is broken. If you know you already have a reference somewhere -
> and I can't find how that would work - you'd have to use __module_get,
> but if it's not you can get a failure from try_module_get legally and
> you should do the try_module_get outside the module, before it's code
> is exectuted.

Ok, I realize - this seems to be confusing. I'll try to clarify:
- First of all, mere mortals are _not_ allowed to compile mandatory
alpha IEEE fp emulation code as a module. Which is documented
in arch/alpha/Kconfig.
- Roughly speaking, the fp emu _module_ code intercepts the fp traps,
so races vs module loading/unloading are fundamentally unavoidable.
These refcounting attempts just narrow the window.

And no, try_module_get should never fail here.

Alternatively, we could just drop _all_ module related stuff from
alpha/math-emu...

Ivan.