Re: [Patch v5 0/9] liblockdep: userspace lockdep

[Sasha Levin]

On 06/27/2013 05:07 AM, Ingo Molnar wrote:
> * Sasha Levin <sasha.levin@xxxxxxxxxx> wrote:
>
> > On 06/26/2013 11:53 AM, Ingo Molnar wrote:
> > > > Ingo, I don't think I see anything holding this back; however I remember
> > > > > reading some email about people not liking stuff like this living in the
> > > > > tools/ directory or such.
> > > > >
> > > > > Will you pick this up?
> > > So I'd really be interested in how interesting/useful this is to userspace
> > > developers? Does it work for something complex as Firefox, or Apache, to
> > > the extent they make use of these locking APIs?
> >
> > So far I've tested it on Firefox, Apache, QEMU, LKVM, GCC and random
> > smallish programs. I haven't really done full testing for each of those,
> > but just made sure that liblockdep behaves as it supposed to. I'm
> > guessing that with further work it will dig up actual issues.
>
> The other issue is that with lock classes disabled you have to hit an
> actual deadlock to trigger any output.
>
> I.e. much of the power of lockdep is diminished :-/ When actual deadlocks
> are triggered then it's not particularly complex to debug user-space apps:
> gdb the hung task(s) and look at the backtraces.

Lock classes are disabled only if you're using the LD_PRELOAD method of
testing. If you actually re-compile your code with the library (by just
including the header and setting a #define to enable it) you will have
lock classes.


Thanks,
Sasha


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