Hi,
I got a little time to look at your current patch (2.6.14-rt21-rf8).
I noticed a problem in futex_wake_robust(). You have a "goto retry" to
solve the following situation:
Task A Task B
takes futex in userspace
Tries to take mutex and sets the
waiting bit in user space
releases futex, notices task B
calls kernel and enters
futex_wake_robust()
retry:
if not owner in rt_mutex
goto retry;
Calls kernel
Makes A owner in rt_mutex
blocks
Leaves retry-loop and
completes the futex wake
operation as normally.
However, if Task A is RT on a UP machine it will go on in the retry loop
forever. Task B will never get the CPU to complete it's kernel-call.
You have probably by manipulating the userspace flag from within the
rt_mutex code :-(
Esben
On Fri, 25 Nov 2005, david singleton wrote:
> There is a new patch, patch-2.6.14-rt15-rf1, that adds support for
> robust and priority inheriting
> pthread_mutexes on the 'heap'.
>
> The previous patches only supported either file based pthread_mutexes
> or mmapped anonymous memory based pthread_mutexes. This patch allows
> pthread_mutexes
> to be 'malloc'ed while using the PTHREAD_MUTEX_ROBUST_NP attribute
> or PTHREAD_PRIO_INHERIT attribute.
>
> The patch can be found at:
>
> http://source.mvista.com/~dsingleton
>
> David
>
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