Userland PI-futex does not work on ARM (2.6.21.5-rt18)

From: Remy Bohmer
Date: Tue Jul 03 2007 - 15:02:00 EST


Hello All,

I am using the 2.6.21.5-rt18 kernel on the ARM core Atmel at91rm9200
together with a Glibc 2.5+GCC4.2.0 toolchain, and I found out that the
userland PI futexes (configured with PTHREAD_PRIO_INHERIT) do not
work.

What happens is:
* Thread A claims the mutex, and gets the lock.
* Thread B claims the mutex, and *also* gets the lock. (this is
obviously already wrong)
* Thread A wants to release the mutex and that fails because it does
not own it...

It looks like mutexes configured *without* PTHREAD_PRIO_INHERIT seem
to work fine, but have not tested that thouroughly.

Is this problem already known, or am I the first person running into it?


Kind Regards,

Remy Böhmer
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