Dear Debian folks,
Am Dienstag, den 03.07.2012, 16:50 +0200 schrieb Paul Menzel: > Package: klogd > Version: 1.5-6.2 > Severity: important > klogd suddenly started to consume 100 % of one CPU core. > > $ ps aux | grep klogd > klog 1731 98.4 0.0 2860 1580 ? Rs 12:50 194:41 > /sbin/klogd -P /var/run/klogd/kmsg > > Due to missing debugging symbols attaching with GDB does not seem to be > that useful. But maybe it is. > > $ sudo gdb --pid 1731 > GNU gdb (GDB) 7.4.1-debian > Copyright (C) 2012 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later > <http://gnu.org/licenses/gpl.html> > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. Type "show > copying" > and "show warranty" for details. > This GDB was configured as "i486-linux-gnu". > For bug reporting instructions, please see: > <http://www.gnu.org/software/gdb/bugs/>. > Attaching to process 1731 > Reading symbols from /sbin/klogd...(no debugging symbols > found)...done. > Reading symbols from > /lib/i386-linux-gnu/i686/cmov/libc.so.6...Reading symbols from > /usr/lib/debug/lib/i386-linux-gnu/i686/cmov/libc-2.13.so...done. > done. > Loaded symbols for /lib/i386-linux-gnu/i686/cmov/libc.so.6 > Reading symbols from /lib/ld-linux.so.2...(no debugging symbols > found)...done. > Loaded symbols for /lib/ld-linux.so.2 > 0xffffe424 in __kernel_vsyscall () > (gdb) bt > #0 0xffffe424 in __kernel_vsyscall () > #1 0xb76f0f53 in __read_nocancel () at > ../sysdeps/unix/syscall-template.S:82 > #2 0x0804a404 in ?? () > #3 0x080496a5 in ?? () > #4 0xb7646e46 in __libc_start_main (main=0x80492e0, argc=3, > ubp_av=0xbf87aee4, init=0x804bff0, fini=0x804bfe0, rtld_fini=0xb77cd590, > stack_end=0xbf87aedc) at libc-start.c:228 > #5 0x08049949 in ?? () > (gdb) c > Continuing. > ^C > Program received signal SIGINT, Interrupt. > 0xffffe424 in __kernel_vsyscall () > (gdb) bt > #0 0xffffe424 in __kernel_vsyscall () > #1 0xb76f0f53 in __read_nocancel () at > ../sysdeps/unix/syscall-template.S:82 > #2 0x0804a404 in ?? () > #3 0x080496a5 in ?? () > #4 0xb7646e46 in __libc_start_main (main=0x80492e0, argc=3, > ubp_av=0xbf87aee4, init=0x804bff0, fini=0x804bfe0, rtld_fini=0xb77cd590, > stack_end=0xbf87aedc) at libc-start.c:228 > #5 0x08049949 in ?? () > (gdb) c > Continuing. > ^C > Program received signal SIGINT, Interrupt. > 0xffffe424 in __kernel_vsyscall () > (gdb) bt > #0 0xffffe424 in __kernel_vsyscall () > #1 0xb76f0f53 in __read_nocancel () at > ../sysdeps/unix/syscall-template.S:82 > #2 0x0804a404 in ?? () > #3 0x080496a5 in ?? () > #4 0xb7646e46 in __libc_start_main (main=0x80492e0, argc=3, > ubp_av=0xbf87aee4, init=0x804bff0, fini=0x804bfe0, rtld_fini=0xb77cd590, > stack_end=0xbf87aedc) at libc-start.c:228 > #5 0x08049949 in ?? () > (gdb) c > Continuing. > ^C > Program received signal SIGINT, Interrupt. > 0xffffe424 in __kernel_vsyscall () > (gdb) quit > A debugging session is active. > > Inferior 1 [process 1731] will be detached. > > Quit anyway? (y or n) y > > It seems to want to read something. The following output was printed > continuously to the terminal when attaching with `strace`. > > $ sudo strace -p 1731 > […] > read(0, "", 4095) = 0 > read(0, "", 4095) = 0 > read(0, "", 4095) = 0 > read(0, "", 4095) = 0 > read(0, "", 4095) = 0 > [several more times] > > Building klogd with debugging symbols and installing the rogue(?) > process was killed. > > $ export DEB_BUILD_OPTIONS="debug" > $ dpkg-buildpackage -us -uc -B > $ sudo dpkg -i ../klogd_1.5-6.2_i386.deb > (Lese Datenbank ... 494344 Dateien und Verzeichnisse sind derzeit > installiert.) > Vorbereitung zum Ersetzen von klogd 1.5-6.2 (durch > ../klogd_1.5-6.2_i386.deb) ... > Ersatz für klogd wird entpackt ... > klogd (1.5-6.2) wird eingerichtet ... > [....] Stopping kernel log daemon...start-stop-daemon: warning: > failed to kill 1729: No such process > 1 pids were not killed > No process in pidfile '/var/run/klogd/kmsgpipe.pid' found running; > none killed. > . ok > [ ok ] Starting kernel log daemon.... > Trigger für man-db werden verarbeitet ... > > Is that a known problem? First this might be the same issue as #308580 [1]. I know of one user also experiencing this problem currently. One theory is that it is related to running the latest Linux kernel. In my case Linux 3.5-rc5+. Running the default Debian Linux kernel 3.2 I have not yet experienced this problem I think. Furthermore the other user also figured out that it loops on /run/klogd/kmsg and that this pipe is closed from one end. When dd’ing /proc/kmsg into that pipe is finished, klogd does not handle the EOF. The current theory is that the construct if ((rdcnt = read(…)) < 0) { […] } is buggy. I have no idea how to fix it though. > I also do not know why and how `/etc/init.d/klogd` was changed. […] Thanks, Paul [1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=308580
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