sebastian.huber at embedded-brains.de
Fri Jun 26 13:42:21 UTC 2015
On 26/06/15 15:28, Gedare Bloom wrote:
> Since this thread got migrated to devel a bit prematurely, I'll
> back-stop some of the details and how I understand the state of this
> Saurabh is working toward solving https://devel.rtems.org/ticket/2124
> (so yes there is a ticket already, and it should be referenced by
> patches accordingly). As a first step he has proposed a modified way
> to step-down inherited priorities when multiple mutexes are acquired
> simultaneously by one thread and contended by others, i.e. nested
> mutex access. We wanted assurance the proposal is sound, so we had him
> implement a model of the current thread synchronization of RTEMS
> within a Java-based model-checking framework, called Java Path Finder,
> or JPF. His model shows the existing error with the current
> STRICT_ORDER option, and then does not show a problem using his
> proposed method for solving nested mutex acquisition.
> However, validating the proposed method apparently required adding a
> global lock around the two linked lists that are used in Saurabh's
> proposed solution. My intuition is that the global lock to protect
> these lists is not a big problem for uniprocessor, and for SMP we
> should prefer to find other solutions at any rate. The lists should
> not be long, and we should be able to find their bounds. One list is
> bounded by the number of mutexes a thread may hold, and the other by
> the number of threads that may contend a specific mutex.
Does this new approach address the problem here:
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.huber at embedded-brains.de
PGP : Public key available on request.
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