l4-hackers September 2005

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

24 participants
20 discussions

Re: What happens on timeslice overrun?
by Udo A. Steinberg 23 Nov '05

23 Nov '05

On Sun, 14 Aug 2005 22:16:09 +0200 Rene Wittmann (RW) wrote: RW> I have 2 questions on the RT part in DROPS: RW> RW> 1.) I have 2 RT working threads, each with 3 timeslices: RW> Thread 1: period=10ms RW> ts1=30ms prio1=50 RW> ts2=10ms prio2=30 RW> ts3=20ms prio3=50 RW> RW> Thread 2: period=10ms RW> ts1=20ms prio1=40 RW> ts2=5ms prio2=30 RW> ts3=10ms prio3=40 RW> RW> Assume both threads … [View More]are ready at the same time. RW> So thread 1 starts and does its work until it RW> releases the voluntarily or it's preempted by RW> its preempter-thread. So say it releases RW> voluntarily after 20ms. When you say "it's preempted by its preempter thread", do you mean the situation when a preempter with a higher priority than the current thread receives a preemption IPC from the kernel and thus preempts the current thread? RW> Who will get the left 10ms? I guess nobody. When a thread is preempted (that means it gets involuntarily descheduled), the remaining time quantum is saved and later restored when the thread is scheduled again. If the thread yields its scheduling context (that means it voluntarily gives it away), the time quantum is no longer available to the thread. A yield can happen in two ways depending on the target thread id specified: 1) if the target ID is the NIL_ID, then the thread yields its active scheduling context to noone - the time is effectively gone. This is what next_reservation does. Note that the kernel checks the user-specified ID, to guard against the case where a thread wants to yield its active scheduling context and the time quantum on that scheduling context expires simultaneously. 2) if the target ID is a valid thread ID in the system, then the action depends on whether the specified thread is ready to run: a) if it is, then the current thread donates the current scheduling context to the specified thread and that thread then becomes the current thread. This is similar to what happens during a donating IPC. b) if the specified thread is not ready, then the current scheduling context is gone, similar to 1) RW> Or can I assign my left time to a specific RW> thread, say ts2 of thread 1, that is has 20ms RW> after recognizing that ts1 was finished 10ms RW> earlier?I could do with l4_rt_change_timeslice(), RW> but this would probably not work for the the RW> current period! (or yes?) A thread can yield the current scheduling context to another thread as described in 2a) above. Note that the thread will yield the current scheduling context (which may not necessarily be the thread's own active scheduling context). As an example consider: A sends a donating IPC to B, now B runs on A's scheduling context. If B yields to C, then C will run on A's time and B will not donate its own scheduling context. If the current scheduling context is in fact the active scheduling context of the donating thread, then realize that the donating thread will likely encounter a timeslice overrun soon after the yield (the donatee will consume the time quantum until it runs out). If you'd rather avoid that, then the donatee will have to yield the scheduling context back to the owner (the original donator) who then has to yield it to noone. Changes to the time quantum of a scheduling context are only visible the next time that scheduling context becomes the current scheduling context. That means if you change the current scheduling context, then the change will not be visible immediately. RW> 2.) Consider we have a deadline miss. And we say RW> l4_rt_next_period(): would it wait for the beginning RW> of the next (which means: RW> period 1: deadline miss RW> period 2: call next period (because we think we're RW> still in period 1)+ wait to end of period RW> period 3: normal work) RW> Or do I have to care that we do not call RW> l4_rt_next_period() in case of a deadline miss? If your thread misses its deadline right before it wanted to call l4_rt_next_period, then l4_rt_next_period blocks the thread until the end of the new period started due to the deadline miss. Since this is likely not what the thread intended to do, it's the preempter's job to handle that situation, e.g. by ex_regs'ing the thread out of it's l4_rt_next_period call. RW> BTW: I compiled the fiasco-kernel with apic+one shot RW> mode. But this should not be relevant for my question. It is indeed not relevant. -Udo. [View Less]

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env.ipc_error: unknown
by Shakthi Kannan 30 Sep '05

30 Sep '05

Greetings! I have been working on the BID tutorial in writing the hiworld example. I was able to complete the exercise :) I just found one compilation error, in "4.3 Client helper library", where it said no member ipc_error for env. Declaration is as follows: CORBA_Environment env = dice_default_environment; One usage in the example is: return -env.ipc_error; I checked l4/tool/dice/include/dice/dice-corba-types.h and for l4x2 version, ipc_error is declared inside a _p union. Hence, … [View More]

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About driver stubs for L4Linux
by Jianjun Shen 29 Sep '05

29 Sep '05

Hello, I try to run multiple L4Linux instances. Dose L4Linux-2.4 or L4Linux-2.6 implement the driver stubs for oshkosh, ide driver and bmodfs? Where can I find them? Thanks! Wei ___________________________________________________________ 雅虎邮箱超强增值服务－2G超大空间、pop3收信、无限量邮件提醒 http://cn.mail.yahoo.com

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l4dm_mem_open call from L4Linux user process
by Julian Grizzard 29 Sep '05

29 Sep '05

All, I've been working with the dataspace calls with the L4Env running x86 Fiasco. I am trying to create a dataspace from a L4Linux user process, but I am having trouble getting the program to compile. Is my Makefile correct for what I am trying to do? Is there any reason I shouldn't be able to link to l4dm_mem_open from a L4Linux user process? Below is my source, Makefile, and compiler error message. Help much appreciated! ---------- SOURCE ---------- #include <l4/dm_mem/dm_mem.h… [View More]> #include <l4/l4rm/l4rm.h> #include <l4/sys/types.h> #include <l4/dm_generic/types.h> int main(int argc, char**argv){ l4dm_dataspace_t ds; void *addr; l4dm_mem_open(L4DM_DEFAULT_DSM,8192,0,0,"L4RM example",&ds); printf("hi\n"); return 0; } ---------- MAKEFILE ---------- PKGDIR ?= ../.. L4DIR ?= $(PKGDIR)/../.. TARGET = $(PKGNAME) MODE = host SYSTEMS = x86-l4v2 x86-l4x0 # list your .c files here SRC_C = main.c LIBCINCDIR = $(addprefix -I,$(L4INCDIR)) # if your server implements the server side of an idl defined in an idl-file # of your package, list the idl file name(s) here (no path needed) SERVERIDL = # list additional library paths and libraries here LIBS = -ldm_generic -ldm_mem include $(L4DIR)/mk/prog.mk ---------- COMPILER ERROR ---------- jgrizza@tomato:~/build_2.6.01/l4/pkg/create_ds/server/src$ make PWD=/home/jgrizza/build_2.6.01/l4/pkg/create_ds/server/src/OBJ-x86_586-l4v2 make -C OBJ-x86_586-l4v2 -f Makefile make[1]: Entering directory `/home/jgrizza/build_2.6.01/l4/pkg/create_ds/server/src/OBJ-x86_586-l4v2' ... Compiling main.o LD_PRELOAD=/home/jgrizza/build_2.6.01/l4/tool/gendep/libgendep.so GENDEP_TARGET=main.o GENDEP_BINARY=cc1 gcc -c -DRAM_BASE=0x0 -DUSE_OSKIT=y -DSYSTEM_x86_586_l4v2 -DARCH_x86 -DCPUTYPE_586 -DL4API_l4v2 -I../../../idl/OBJ-x86-l4v2 -I../../../../../include/x86/l4v2 -I/home/jgrizza/build_2.6.01/drops/include/x86/l4v2 -I../../../../../include/l4v2 -I/home/jgrizza/build_2.6.01/drops/include/l4v2 -I../../../../../include/x86 -I/home/jgrizza/build_2.6.01/drops/include/x86 -I../../../../../include -I/home/jgrizza/build_2.6.01/drops/include -gstabs+ -g -O2 -fno-strict-aliasing -march=i586 -Wall -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations /home/jgrizza/build_2.6.01/l4/pkg/create_ds/server/src/main.c -o main.o /home/jgrizza/build_2.6.01/l4/pkg/create_ds/server/src/main.c: In function `main': /home/jgrizza/build_2.6.01/l4/pkg/create_ds/server/src/main.c:12: warning: implicit declaration of function `printf' /home/jgrizza/build_2.6.01/l4/pkg/create_ds/server/src/main.c:9: warning: unused variable `addr' ==> Linking create_ds LD_PRELOAD=/home/jgrizza/build_2.6.01/l4/tool/gendep/libgendep.so GENDEP_TARGET=create_ds GENDEP_BINARY=ld gcc -o create_ds main.o -L../../../../../lib/x86_586/l4v2 -L/home/jgrizza/build_2.6.01/drops/lib/x86_586/l4v2 -L../../../../../lib/x86_586 -L/home/jgrizza/build_2.6.01/drops/lib/x86_586 -L../../../../../lib -L/home/jgrizza/build_2.6.01/drops/lib -ldm_generic -ldm_mem ../../../../../lib/x86_586/l4v2/libdm_mem.a(open.o)(.text+0xba): In function `l4dm_mem_open': /home/jgrizza/build_2.6.01/l4/pkg/dm_mem/lib/clientlib/src/open.c:87: undefined reference to `LOG_logL' ../../../../../lib/x86_586/l4v2/libdm_mem.a(open.o)(.text+0xff):/home/jgrizza/build_2.6.01/l4/pkg/dm_mem/lib/clientlib/src/open.c:62: undefined reference to `l4env_get_default_dsm' ../../../../../lib/x86_586/l4v2/libdm_mem.a(open.o)(.text+0x12b):/home/jgrizza/build_2.6.01/l4/pkg/dm_mem/lib/clientlib/src/open.c:65: undefined reference to `LOG_logL' collect2: ld returned 1 exit status make[1]: *** [create_ds] Error 1 make[1]: Leaving directory `/home/jgrizza/build_2.6.01/l4/pkg/create_ds/server/src/OBJ-x86_586-l4v2' make: *** [OBJ-x86_586-l4v2] Error 2 Thanks! Julian [View Less]

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names memory overlap error
by Shakthi Kannan 28 Sep '05

28 Sep '05

Greetings! Just started playing around with fiasco and l4env. I checked out l4env and hello from CVS, which obtained all the required files. I was able to compile it on my x86 Thinkpad (T41) running Debian Sarge 3.1r0a. I've added an entry in boot/grub/menu.lst as follows: title DROPS/Fiasco u-kernel kernel (hd0,0)/boot/fiasco/rmgr -sigma0 module (hd0,0)/boot/fiasco/main -noserial -nowait -nokdb module (hd0,0)/boot/fiasco/sigma0 module (hd0,0)/boot/fiasco/names module (hd0,0)/boot/… [View More]

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[ANN] Fiasco 1.2 released
by Adam Lackorzynski 26 Sep '05

26 Sep '05

The operating system's group at Technische Universität Dresden is pleased to announce the release of version 1.2 of the Fiasco L4 microkernel. Since the last release Fiasco has significantly matured and is now thought to be the most stable version available. For a comprehensive list of changes please consult the CHANGES file in the distribution. Highlights are the integration of scheduling extensions targeted at real-time applications, better support for paravirtualised systems as well as … [View More]

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Did not find VBE info block
by Shakthi Kannan 26 Sep '05

26 Sep '05

Greetings! I am trying to get the console using l4env and fiasco on an old x86 desktop. Is it like the bash shell? Images have been compiled from CVS sources. All images are booted from the grub present in the demo floppy. The grub entry is as follows: kernel (fd0)/l4/v2/rmgr -sigma0 modaddr 0x01500000 kernel (fd0)/l4/v2/main -noserial -nowait -nokdb kernel (fd0)/l4/v2/sigma0 kernel (fd0)/l4/v2/names kernel (fd0)/l4/v2/log kernel (fd0)/l4/v2/dm_phys kernel (fd0)/l4/v2/con The output that I … [View More]

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Problems porting L4Linux 2.4 module to 2.6
by Derick Swanepoel 22 Sep '05

22 Sep '05

Hi, I'm trying to convert a custom kernel 2.4 module to 2.6. The most serious problem I'm having is that there are now some unresolved symbols with 2.6: *** Warning: "l4rm_detach" [/home/drops/DROPS-20050908/l4/pkg/test/examples/module.ko] undefined! *** Warning: "kmalloc" [/home/drops/DROPS-20050908/l4/pkg/test/examples/module.ko] undefined! *** Warning: "l4rm_do_attach" [/home/drops/DROPS-20050908/l4/pkg/test/examples/module.ko] undefined! *** Warning: "l4env_err_ipcstrings" [/home/drops/… [View More]

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Problem with hybrid L4Linux task
by Mathias Krause 19 Sep '05

19 Sep '05

Hello Hackers, I've got a problem with a hybrid Linux Task. I want to create a little tool to tranfser data between two L4Linuxes easily. A tool similar to the famous netcat but using IPC instead of UDP/TCP. So far so good. Server is listen for client and client is sending data to the server (using long IPC transfering data as dwords). The problem is that the data doesn't arrive at the server task. There only an empty IPC message gets received (no IPC error). After I've played around a … [View More]

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Compiling DROPS' dietlibc on FreeBSD
by Julian Stecklina 15 Sep '05

15 Sep '05

Hello, after changing minimal parts of dietlibc's build procedure, I get as far as cd pkg/dietlibc ; gmake actually doing something but it fails with the following error: ... Compiling lib/__v_printf.o LD_PRELOAD=/home/blitz/src/l4/tool/gendep/libgendep.so GENDEP_TARGET=lib/__v_printf.o GENDEP_BINARY=cc1 gcc33 -c -nostdinc -DRAM_BASE=0x0 -DUSE_DIETLIBC=y -DSYSTEM_x86_686 -DARCH_x86 -DCPUTYPE_686 -DL4API_ -I../include -I.. -I../../../idl/OBJ-x86- -I/include -gstabs+ -g -O2 -fno-… [View More]

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l4-hackers September 2005