Messages in this thread | | | Date | Tue, 01 Dec 2009 08:16:10 -0800 | From | Darren Hart <> | Subject | Re: [RFC] [PATCH 0/2] Futex fault injection |
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Ingo Molnar wrote: > * Peter Zijlstra <peterz@infradead.org> wrote: > >> On Tue, 2009-12-01 at 11:33 +0100, Ingo Molnar wrote: >>> * Sripathi Kodi <sripathik@in.ibm.com> wrote: >>> >>>> Hi, >>>> >>>> This patch set adds fault injection for futex subsystem. It adds >>>> faults at places where reading/writing from user space can return >>>> EFAULT. This will be useful in testing any significant change to futex >>>> subsystem. >>> Instead of this unacceptably ugly and special-purpose debugfs >>> interface, please extend perf events to allow event injection. Some >>> other places in the kernel (which deal with rare events) want/need >>> this capability too. >> Thing is, he's using the 'normal' fault injection code to do this, I >> see no objection to doing that. > > Yes - but its impact to the futex code is butt-ugly. That some facility > is in the kernel does not mean it gets a free pass to be applied > everywhere and anywhere.
I don't think the "butt-ugly" argument is enough to reject the patch. It's a fairly subjective metric and I don't think the proposed solution results in "pretty" code either. In fact the super long function names and multi-line conditionals are arguably "ugly" (maybe not "butt-ugly" though). :-)
However, the arguments are solid and I understand wanting to introduce a new feature in a particular way. Has there been any work done on perf event injection up to this point or would this be a completely new perf feature?
-- Darren
> > An example of that would be tracepoints - there's no free pass to add > tracepoints in new places and some maintainers elect to use different > facilities. (or reject all current facilities) > >> If you want to redo the fault injection subsystem, then that's another >> story, but then we need to convert all of its users over. > > What i want to see is sane code in futex.c. If we add hooks/callbacks > i'd like it to be a complete solution helping a lot of usecases not some > limited approach helping testability only. > > Thanks, > > Ingo
-- Darren Hart IBM Linux Technology Center Real-Time Linux Team
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