On Thursday 04 July 2002 02:29, pmenage@ensim.com wrote:
> In article <0C01A29FBAE24448A792F5C68F5EA47D2B0A8A@nasdaq.ms.ensim.com>,
> you write:
> >
> >Is it just the mod_dec_use_count; return/unload race we're worried about?
> >>I'm not clear on why this is hard. I'd think it would be sufficient just to
> >walk all runnable processes to ensure none has an execution address inside
> >the module. For smp, an ipi would pick up the current process on each cpu.
> >
> >At this point the use count must be zero and the module deregistered, so
> >all we're interested in is that every process that dec'ed the module's use
> >count has succeeded in executing its way out of the module. If not, we try
> >again later, or if we're impatient, also bump any processes still inside the
> >module to the front of the run queue.
> >
> >I'm sure I must have missed something.
>
> Identifying the valid execution address in a stack traceback isn't
> possible on many architectures (in particular, i386 without debugging
> support enabled) so this wouldn't work if one of the functions had
> called into a function outside the module.
I'm only thinking about the current execution address, and am only
concerned with the handful of instructions between the dec and the
ret. But I did miss something all right: I'd assumed we somehow
magically wrap all exported functions in inc/dec, which on closer
inspection, isn't the case.
> On the other hand, if it was made a rule that any code in a module that
> might theoretically be running without reference counts wasn't allowed
> to call out of the module (or maybe was allowed to call out to a very
> specific small set of library functions that were known to the module
> system), then something like this might work.
That seems like a reasonable rule to make. This, along with the
execution address inspection, would give us a way of declaring
certain modules 'remove clean'. Module removal is just too nice a
feature to give up on so easily.
What else did I miss?
-- Daniel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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