On 12.11.2012 14:28, Udo Steinberg wrote: > On Mon, 12 Nov 2012 12:24:04 +0100 Alexander Boettcher (AB) wrote: > > AB> On 12.11.2012 10:27, Norman Feske wrote: > AB> > processes the execution flows through. As far as I know, NOVA is the > AB> > only kernel of the Genode base platforms that properly implements > AB> > priority inheritance. > AB> Just some note for completeness: This is solely implemented for the IPC > AB> mechanism of the kernel, however it is not supported for the semaphores > AB> provided by the kernel. That means if semaphores are used as locks to > AB> protect some critical section in user mode, the thread running inside > AB> the critical section (and holding the lock) doesn't inherit the priority > AB> of other threads also attempting to get into the same critical section. > > We don't do it for semaphores, because semaphores can be used from different > cores and cross-core inheritance doesn't work. We could add some limited > form of local inheritance to semaphores, e.g. threads on the same core could > help each other. > > But - having only core-local inheritance for semaphores could lead to odd > behavior, such as programs working as expected on a single-core machine and > breaking when running on a multi-core machine, because a developer may have > built assumptions about priority inheritance into their code. > > So... how useful would core-local inheritance for semaphores be?
IMHO - it is not useful. Since semaphores can be used cross CPU, priority inheritance either works * for semaphores on uni- as multi CPU systems or * it doesn't work at all for semaphores. Currently it does not - which is consequent. Alex. > > Cheers, > Udo > > > > ------------------------------------------------------------------------------ > Everyone hates slow websites. So do we. > Make your web apps faster with AppDynamics > Download AppDynamics Lite for free today: > http://p.sf.net/sfu/appdyn_d2d_nov > > > > _______________________________________________ > Genode-main mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/genode-main > ------------------------------------------------------------------------------ Monitor your physical, virtual and cloud infrastructure from a single web console. Get in-depth insight into apps, servers, databases, vmware, SAP, cloud infrastructure, etc. Download 30-day Free Trial. Pricing starts from $795 for 25 servers or applications! http://p.sf.net/sfu/zoho_dev2dev_nov _______________________________________________ Genode-main mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/genode-main
