users October 2009

users@lists.genode.org

4 participants
3 discussions

Sharing locks between several address spaces
by Sven Fülster 20 Oct '09

20 Oct '09

Hi there, I'm working on two applications which require communication over shared memory. Therefore, I've adapted some of your datastructures (such as the slab allocator, semaphores and locks) so that they are safe to be shared between different address spaces, by adding smart pointers and taking care of having all shared components (like the Applicant list of the locks, the applicants and the locks themselves) within the shared memory. I have now a little problem with the locks. I have a thread in address space 1 which performs a lock operation on a lock in shared memory. The lock operation is (by default) mapped to the L4_Stop syscall (I work with the Okl4-Kernel). Another thread in address space 2 performs a wake-operation on the same lock (where the thread id is deposited in the applicant), which is mapped to L4_ThreadSwitch which is again mapped to the L4_ExchangeRegisters syscall. This operation does not wake the first thread. In detail, the L4_ThreadWasHalted call which is performed upon L4_ThreadSwitch returns false, hence the thread which tried the wake operation remains spinning in the forever-loop (this is a nice opportunity for a denial-of-service-attac of a malicious client by the way...). However, I've started to investigate by replacing the L4_ThreadSwitch syscall by L4_WaitNotify and the wake-operation by L4_Notify. The result was the same. Checking the error code of the L4_Notify syscall with L4_ErrorCode showed that the call had been aborted due to L4_ErrInvalidThread, respectively L4_ErrNonExist (2). Now I wonder if a thread is generally allowed to invoke syscalls on threads which don't belong to its address space (maybe I need some capability? What exactly is env()->pd_session()->bind_thread() for?). I've also noticed that the thread ids I get from env()->cpu_session()->state() or from thread_get_my_native_id() differ from those the kernel debugger shows (what exactly do you do when you ask Okl4::__L4_TCR_ThreadWord(Genode::UTCB_TCR_THREAD_WORD_MYSELF) for a thread id? Is that the global thread id?) Perhaps you have an idea what's going wrong here (meanwhile I'd add L4_MutexControl to core :o) ). With kind regards Sven -- Sven FÃ¼lster

2 1

Re: Split console with two keyboards
by Christian Helmuth 16 Oct '09

16 Oct '09

Hello Shakthi, On Fri, Oct 16, 2009 at 12:16:21AM +0530, Shakthi Kannan wrote: > Hi, > > I would like to know if it is possible in any of the L4* systems to > have a setup like the following: > > * The console (framebuffer) to be split into two frames/windows, say > top and bottom halves, but, each one should be used/accessed > independently of each other. > > * With two keyboards connected to this single system, one should be > able to use (shell) one of the keyboards with the top window, while > the other should use the bottom one. > > Appreciate any thoughts/inputs in this regard. Thanks! I don't know of any L4-based system, which supports this setup out-of-the-box. IMO Genode [1] and L4Env [2] have all you need to build such a system on your own: PS/2 drivers, USB HID drivers, and frame buffer console/GUI. Both options implicate some hacking on your part as multi-head scenarios were not addressed so far. BTW, Genode seemlessly supports several L4 kernels, namely OKL4, Fiasco, and Pistachio. That's a nice feature if you're not certain which kernel fits your needs best and want to postpone the final decision :-) [1] http://www.genode.org [2] http://www.inf.tu-dresden.de/index.php?node_id=1431 Regards -- Christian Helmuth Genode Labs http://www.genode-labs.com/ · http://genode.org/

1 0

Small TODO tasks at Genode project
by Shakthi Kannan 06 Oct '09

06 Oct '09

Hi, I am looking at small tasks that can be worked for the Genode project. Is it possible for anyone to break down larger goals into smaller project outcomes that people can explore or delve into? Also, this FPGA graphics is quite interesting. What is the content in the FPGA here, and what is the relation with Genode here? Sorry, if this is off-topic in this list, else I shall contact the Genode-FX list. http://www.genode-labs.com/news/genode-fx-on-trenz-electronic-industrial-fp… Thanks! SK -- Shakthi Kannan http://www.shakthimaan.com

2 4

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

users October 2009