l4-hackers August 2005

l4-hackers@os.inf.tu-dresden.de

25 participants
31 discussions

What happens on timeslice overrun?
by Rene Wittmann 14 Aug '05

14 Aug '05

Hi, I have 2 questions on the RT part in DROPS: 1.) I have 2 RT working threads, each with 3 timeslices: Thread 1: period=10ms ts1=30ms prio1=50 ts2=10ms prio2=30 ts3=20ms prio3=50 Thread 2: period=10ms ts1=20ms prio1=40 ts2=5ms prio2=30 ts3=10ms prio3=40 Assume both threads are ready at the same time. So thread 1 starts and does its work until it releases the voluntarily or it's preempted by its preempter-thread. So say it releases voluntarily after 20ms. Who will get the left 10ms? I guess nobody. Or can I assign my left time to a specific thread, say ts2 of thread 1, that is has 20ms after recognizing that ts1 was finished 10ms earlier?I could do with l4_rt_change_timeslice(), but this would probably not work for the the current period! (or yes?) I could even imagine that it would work in my case described above, as thread 2 would be next after ts1 of thread 1, but consider thread 2 didn't exist... 2.) Consider we have a deadline miss. And we say l4_rt_next_period(): would it wait for the beginning of the next (which means: period 1: deadline miss period 2: call next period (because we think we're still in period 1)+ wait to end of period period 3: normal work) Or do I have to care that we do not call l4_rt_next_period() in case of a deadline miss? BTW: I compiled the fiasco-kernel with apic+one shot mode. But this should not be relevant for my question. Regards, Rene

1 0

Re: Logging/printf's in RT env
by Rene Wittmann 10 Aug '05

10 Aug '05

Hi, first of all: sorry for my late answer, I've been away... On Thu, Aug 04, 2005 at 03:09:12PM +0200, Adam Lackorzynski wrote: > On Thu Aug 04, 2005 at 13:45:12 +0200, Rene Wittmann wrote: > > I have also the problem that I want to output some of my symbols+values > > during the execution of my application. > > Furthermore I'm working in the RT scheduling mode (with APIC one shot > > mode). > > > > I have three timeslices: > > 1. mandatory > > 2. optional > > 3. "mandatory" (if part of optional was executed) > > > > The preempter recognizes timeslice overruns and sets a > > global variable, the working thread checks this variable and therefore > > knows about those "events". > > > > This works fine if my priorites are set to 50,30,50, > > but fails after a few periods with a pagefault if setting the priorities to > > 200,190,200. > > > > In each part I use some calls to LOG() to output a few things I'm > > interested in. If I leave out those LOG()-calls, it works also with the > > high priorites (200,190,200). > > So I assume, there's a LOG-buffer overflow (as the LOG priority is not > > that high)? > > > > Could I prevent this by using printf instead of LOG or is LOG just a > > kind of macro for printf? > > printf is usually also a log function. > > The priorities of the logserver are at 32, so in the first example > they're inbetween and in the latter one completely below. > > Does the PF go away when you add --prio 210 (or similar) as an argument > to log? > Yes, it goes away. But I thought that, if you have a real-time application running it will not be influenced by some "time-sharing" application as the logserver should be. > Can you send me a backtrace with unstripped binaries when the PF > happens? Thanks. > Sure, I can if you tell me how to do it... The exact error message is: app| L4RM: [PF] write at 0x01306f58, eip 0380e48b, src 9.02 app| [9.0] l4rm/lib/src/pagefault.c:78:__unknown_pf(): app| unhandled page fault And then it enters the kernel debugger. I've compiled my program with "CFLAGS = -g" so it should be unstripped, right? But when typing "bt<CR>" in the kernel debugger, there are no symbols and the output just looks like this #4 f000763b #5 f0027332 #6 f000e718 #7 f000627a #8 f000e1fd #9 f000627a #10 f000e1fd #11 f000acb0 #12 f0005f6d #13 f000627a #14 f0006280 #15 f0005c3f #16 f000627a #17 f0006280 #18 f0005aec #19 f999c5f5 #20 f00176ed #21 f0006d54 #22 f0027300 #23 f000cfa5 #24 f0006a5a #25 f000784b #26 f00272dc So I don't expect any helpful information in there or is it? BTW: my grub config looks like this: title llv1_decode (all layers, log locally) root (hd0,2) kernel /drops/bin/x86_586/l4v2/rmgr -sigma0 modaddr 0x08000000 module /l4/kernel/fiasco/build/fiasco_apic -nokdb -nowait -serial -serial_esc module /drops/bin/x86_586/l4v2/sigma0 module /drops/bin/x86_586/l4v2/log_net -net -local -ip 131.188.36.211 -buffer 4096 module /drops/bin/x86_586/l4v2/names module /drops/bin/x86_586/l4v2/dm_phys module /drops/bin/x86_586/l4v2/simple_ts module /drops/bin/x86_586/l4v2/app OK, this modaddr seems huge, but my data is just linked to the binary and I need this huge value... So how would one produce a useful backtrace inside fiasco? Or is there a way to use another debugger (gdb?)? Greetings, Rene

4 4

Fiasco + L4Linux auf echter Hardware
by Marcel Selhorst 09 Aug '05

09 Aug '05

Hallo L4-Hackers, ich kämpfe nunmehr seit drei Tagen mit dem Versuch, Fiasco+L4Linux auf echter Hardware (Pentium 4, 512MB RAM) ans Laufen zu bekommen. Was sich ursprünglich als leichtes Unterfangen anbahnte, entpuppte sich hinlänglich als 'Fiasco' und ich bin mit meinem Latein am Ende :-) Folgende (hoffentlich einfache) Frage: Welche Einstellungen muss man im Fiasco-Kern treffen (mit welchen Experimental- Optionen), und welche im L4Linux, um es gemeinsam ans Laufen zu bekommen? Gibt es zu den einzelnen Optionen irgendwo detailliertere Dokumentationen außer der ein- bis zweizeiligen Onlinehilfe im "make menuconfig"? Ursprüngliche Kompilierungsschwierigkeiten ließen sich durch zwei CVS-Updates an zwei aufeinanderfolgenden Tagen beheben, aber der fiasco bleibt jedesmal beim booten von L4Linux stehen und friert ein, _bevor_ das eigentliche Linux-Fenster in Dope geöffnet wird. Im dmon steht als letzte Zeile: =====> L4Linux 2.6 starting <======= Hoffnungsvolle Grüße, Marcel Selhorst

3 6

Some broken packages in remote-cvs
by Arthur Mielimonka 04 Aug '05

04 Aug '05

Hi, I checked out L4 and tried to compile it. There are some broken packages, which don't compile: /l4/pkg/cpu_reserve/examples/utcb-watch /l4/pkg/loader/examples/fprov-l4 /l4/pkg/dmon/server /l4/pkg/dsi_staticfs /l4/pkg/rt_mon/examples/dope_mon /l4/pkg/rt_mon/examples/l4vfs_dope_mon/ Just to inform you. Bye, Arthur

3 4

Logging/printf's in RT env
by Rene Wittmann 04 Aug '05

04 Aug '05

Hi, I have also the problem that I want to output some of my symbols+values during the execution of my application. Furthermore I'm working in the RT scheduling mode (with APIC one shot mode). I have three timeslices: 1. mandatory 2. optional 3. "mandatory" (if part of optional was executed) The preempter recognizes timeslice overruns and sets a global variable, the working thread checks this variable and therefore knows about those "events". This works fine if my priorites are set to 50,30,50, but fails after a few periods with a pagefault if setting the priorities to 200,190,200. In each part I use some calls to LOG() to output a few things I'm interested in. If I leave out those LOG()-calls, it works also with the high priorites (200,190,200). So I assume, there's a LOG-buffer overflow (as the LOG priority is not that high)? Could I prevent this by using printf instead of LOG or is LOG just a kind of macro for printf? Regards, Rene

2 1

remote gdb stub
by Bert van Leeuwen 04 Aug '05

04 Aug '05

Is there a tutorial or guide somewhere about how to use remote gdb (from a linux machine) to debug an L4 task? I haven't been able to find much more info about this other than casual mention that it is supported...

3 5

i can't find filesystem server pkg and SCSI driver pkg in your CVS
by 강후영 03 Aug '05

03 Aug '05

3 2

kill-l4 fails to kill a task started with run-l4
by Derick Swanepoel 03 Aug '05

03 Aug '05

Hi all, I am using kill-l4 to try and kill a task started with run-l4, but it fails as follows: simplets| l4_ts_kill_recursive_component(): Kill 21.00 sent by 20.00 owner 20.00 simplets| task_kill(): Kill 21.00 from 20.00 but owner is 20.00 | l4ts_kill_task_recursive(): failed (server=8.00, ret=-11, exc 0) Any ideas? Thanks, Derick

2 1

I retry to send mail.. sorry encoding problem..
by ??? 02 Aug '05

02 Aug '05

hello~! I am master course student of pohang university of science and technology in korea I try to l4 testing on fiasco and i have a question.. my machine is only one (now, not used flips NIC) I like to tests that write to SCSI hard disk. I think that this work needs to filesystem server and SCSI driver but i can't find filesystem server pkg and SCSI driver pkg in your CVS how do i get this packages please help me i am looking forward to your answer thank

1 0

i can't find filesystem server pkg and SCSI driver pkg in your CVS
by 강후영 02 Aug '05

02 Aug '05

hello~! I am master course student of pohang university of science and technology in korea   I try to l4 testing on fiasco and i have a question..   my machine is only one (now, not used flips NIC) I like to tests that write to SCSI hard disk.   I think that this work needs to filesystem server and SCSI driver but i can't find filesystem server pkg and SCSI driver pkg in your CVS   how do i get this packages   please help me   thank

1 0

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l4-hackers August 2005