RE: [PATCH] Priority Lists for the RT mutex

[Perez-Gonzalez, Inaky]

>From: Bill Huey (hui) [mailto:bhuey@xxxxxxxx]
>
>On Mon, Apr 11, 2005 at 10:57:37AM +0200, Ingo Molnar wrote:
>>
>> * Perez-Gonzalez, Inaky <inaky.perez-gonzalez@xxxxxxxxx> wrote:
>>
>> > Let me re-phrase then: it is a must have only on PI, to make sure
you
>> > don't have a loop when doing it. Maybe is a consequence of the
>> > algorithm I chose. -However- it should be possible to disable it in
>> > cases where you are reasonably sure it won't happen (such as kernel
>> > code). In any case, AFAIR, I still did not implement it.
>>
>> are there cases where userspace wants to disable deadlock-detection
for
>> its own locks?
>
>I'd disable it for userspace locks. There might be folks that want to
>implement userspace drivers, but I can't imagine it being 'ok' to have
>the kernel call out to userspace and have it block correctly. I would
>expect them to do something else that's less drastic.

If you are exposing the kernel locks to userspace to implement
mutexes (eg POSIX mutexes), deadlock checking is a feature you want
to have to complain with POSIX. According to some off the record
requirements I've been given, some applications badly need it (I have 
a hard time believing that they are so broken, but heck...).

-- Inaky
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