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

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Date:	Tue, 3 Jul 2007 21:01:50 +0200
From:	"Remy Bohmer" <l.pinguin@...il.com>
To:	linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-kernel@...r.kernel.org
Cc:	andrew@...people.com, "Ingo Molnar" <mingo@...e.hu>,
	"Daniel Walker" <dwalker@...sta.com>
Subject: Userland PI-futex does not work on ARM (2.6.21.5-rt18)

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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