Messages in this thread | | | From | "Serge Noiraud" <> | Subject | Re: RT question : softirq and minimal user RT priority | Date | Fri, 20 Jan 2006 09:24:24 +0100 |
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Hi,
I reproduce the problem without the script command too. I use the tee /dev/ttyS0. It seems the problem is related to a TIMEOUT value somewhere in the buffer management or the scsi driver. The test is 34 minutes ( 2040 sec ) long on my machine. ( HP workstation xw8200 ). I found 1800 sec Time out in the kernel, but not for my drivers.
What kind of test or debug could I use to find out the problem ?
mardi 17 Janvier 2006 08:58, Serge Noiraud wrote/a écrit : > Hi, > I continue my tests and found something new. I tested -rt6 : same problem > > vendredi 13 Janvier 2006 16:53, Steven Rostedt wrote/a écrit : > > On Fri, 2006-01-13 at 15:27 +0100, Serge Noiraud wrote: > > > Hi, > > > > > > I was testing 2.6.15-rt3. During my tests, I tried to run a program which made a loop at > > > RT priority 10 and 30. > > > > So you have two programs running, one at priority 10 and 30 right? > I can reproduce the problem easily after each reboot at any priority with only one program. > The problem occurs if all the IRQ's are affected to CPU 0 ( smp_affinity ) and the test run on CPU 0. > Only one program which makes 60000000000ULL loops. > Before I run this program, I type the command script to keep the results. > When the test stop, I quit the script command <ctrl>d. > I am in the standard shell. > The result file from the script command is empty. This is how I find the problem. > > I tried with 2.6.15-rt6 : same problem. > > > > > > I was very happy to see that after the tests, I can't use any command except those already in memory. > > > > So, are these programs still running? Are they in busy loops? > No they are finished. > > > > > My filesystems were in read-only after the test. I was unable to shutdown the machine : > > > > How did the filesystems go into read-only? Did the tests do that? > No, it's a simple loop in which I get tsc to evaluate system perturbations. > after quiting the script command, I can't type any command. That's what I mean below. > > > > > top => command not found > > > <CTRL><ALT><DEL> => INIT: cannot execute "/sbin/shutdown" > > > /sbin/reboot => Input/Output error > > > I had to push the reset button. > > > > I'll need more info to understand these. > I have no more access to the file system. I can only do less and some other command. > I get Input/Output error for all new command not in memory. > If I try to ssh from another machine, I obtain the following messages : > [root@dist2 root]# ssh dist1 > root@dist1's password: > Last login: Mon Jan 16 11:13:49 2006 from dist2.btsn.xxxxxxxxxx > /usr/X11R6/bin/xauth: error in locking authority file /root/.Xauthority > I can't access .Xauthority file which exists. I could access it before the test. > > At this point, If I try to reboot, I get the following messages. > <CTRL><ALT><DEL> => INIT: cannot execute "/sbin/shutdown" > /sbin/reboot => Input/Output error > > Before launching the script and the test, the system works correctly. > > If I reboot the system and I launch the test again, I get the same problem => easily reproductible > > I send you my CONFIG file and the program to reproduce the problem. > > > > > > > > My questions are : > > > Did I find a bug ? > > > > Don't know yet. > > > > > Is the smallest usable real-time priority greater than the highest real-time softirq ? > > > > Nope, you can use any rt priority you want. It's up to you whether you > > want to preempt the softirqs or not. Be careful, timers may be preempted > > from delivering signals to high priority processes. I have a patch to > > fix this, but I'm waiting on input from either Thomas Gleixner or Ingo. > Effectively, the problem occurs whatever the priority is : 10, 30, 60 or 99. > > > > > > In this case could we forbid priority lesser than the highest softirq priority ? > > > > No need. > > > > -- Steve > > Serge Noiraud - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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