I'm creating a new thread, because all the existing screen saver problems dont address my problem
Problem:
On my laptop, many different screen saver will start and sometimes will eat-up all CPU time, at this point, the screen saver process is jammed somewhere in an kernel call, thus, even if I press a key, the screen saver owns the keyboard and mouse inputs and totally prevents me from unlocking it, and thus prevents me from opening a tty shell CTRL-ALT-F?
Often I had to use a power reset
to reboot the laptop...quite embarrassing for a unix system
Based on an strace log, I'm pretty sure the screen saver hangs in a select() kernel call...but why ???
Note, when the laptop jams, I can ssh to it and login and kill the faulty screen saver process
Via ssh, before killing the process, I tried to attach to it using gdb, but even gdb cant attach, it tries, but I never get a prompt...so I cant do "where"
Sometimes I dont have the luxury of having another PC to ssh !
Pls dont tell me to simply disable the screen saver, I saw that lame solution many times in other threads, The reason I'm posting this, is to find a solution, and exchange with resourceful people ! ...maybe learn something in the process, and to improve Linux
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Here is the latest development,
I made a cron job that monitors for a greedy screen saver process and does a few things when this occurs
1- it attaches an strace to it
2- it checks the CPU usage and will kill if required
using SIGABRT (to crate a core dump)
...all this, going to log files
To ease the cron job, I forced the keuphoria.kss screen saver (instead of having a random one)
below I'm pasting the strace log and a "ps" extract
So now, I'm pretty sure it hangs in the select() kernel call that usually times-out...
But I'm kinda stuck, I'm not sure what I can do next, it looks like a kernel problem, I dont think a process should hang so deep that even gdb cant attach to it...
Is it possible that for a reason, the select() call sometimes does not time-out?
STRACE LOG: (last lines)
read(3, 0x6518f4, 4096) = -1 EAGAIN (Resource temporarily unavailable)
select(14, [3 4 7 9 13], [], [], {0, 378}) = 0 (Timeout)
ioctl(14, 0x4008642a, 0x7ffff76839d0) = 0
ioctl(14, 0xc0086444, 0x7ffff7683970) = 0
ioctl(14, 0x40046445, 0x7ffff7683960) = 0
ioctl(14, 0x40206443, 0x7ffff7683a10) = 0
ioctl(14, 0xc0086444, 0x7ffff76839c0) = 0
ioctl(14, 0xc0086444, 0x7ffff7683970) = 0
ioctl(14, 0x40046445, 0x7ffff7683960) = 0
ioctl(14, 0x40206443, 0x7ffff7683a10) = 0
ioctl(14, 0xc0086444, 0x7ffff76839c0) = 0
brk(0xd10000) = 0xd10000
brk(0xd50000) = 0xd50000
ioctl(14, 0xc0086444, 0x7ffff7683ad0) = 0
ioctl(14, 0x40046445, 0x7ffff7683ac0) = 0
ioctl(14, 0xc0086444, 0x7ffff7683ad0) = 0
ioctl(14, 0x40046445, 0x7ffff7683ac0) = 0
ioctl(14, 0xc0086444, 0x7ffff7683b10) = 0
ioctl(14, 0x40046445, 0x7ffff7683b00) = 0
ioctl(14, 0x40206443, 0x7ffff7683bb0) = 0
ioctl(14, 0xc0086444, 0x7ffff7683b60) = 0
ioctl(14, 0xc0086444, 0x7ffff76839c0) = 0
ioctl(14, 0x40046445, 0x7ffff76839b0) = 0
ioctl(14, 0x40206443, 0x7ffff7683a60) = 0
ioctl(14, 0xc0086444, 0x7ffff7683a10) = 0
ioctl(14, 0x6458, 0) = -1 EINVAL (Invalid argument)
select(4, [3], [3], NULL, NULL) = 1 (out [3])
writev(3, [{"\227\5\6\0\233\2 \4\26\10\"\5\1\0\1\0.\6#\5\351\1.\0\234\4\3\0|\0\0 \0"..., 44}], 1) = 44
read(3, 0x6518f4, 4096) = -1 EAGAIN (Resource temporarily unavailable)
select(14, [3 4 7 9 13], [], [], {0, 15323}) = 0 (Timeout)
read(3, 0x6518f4, 4096) = -1 EAGAIN (Resource temporarily unavailable)
select(14, [3 4 7 9 13], [], [], {0, 33}) = 0 (Timeout)
--- SIGINT (Interrupt) @ 0 (0) ---
Process 6061 detached
^^^^---- The cron job sends a SIGABRT to force a core dump, but from strace, it looks like I receive a SIGINT
*** and no core file is generated anywhere
-------
LOG of "ps" just before the cron job kills the screen saver:
F S UID PID PPID C PRI NI ADDR SZ WCHAN STIME TTY TIME CMD
...
1 S pmichel 4524 1 0 80 0 - 38176 - 08:19 ? 00:00:01 kdesktop [kdeinit]
0 S pmichel 7378 4524 0 80 0 - 33084 - 08:49 ? 00:00:00 /opt/kde3/bin/kdesktop_lock
0 R pmichel 7381 7378 58 99 19 - 31684 - 08:49 ? 00:02:11 /opt/kde3/bin/keuphoria.kss -root
^^^--- see keuphoria uses 99% cpu time
Thanks for your inputs