screen saver hangs in select() call - - kernel problem?

[pmichelmp3]

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

--------------------------------------

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

[pmichelmp3]

I've just noticed that the last strace line shows " = 0 "
so this means that select() did return
and based on the strace history of previous events,
I assume that the screen saver is stuck in the iocl() call that should normally follow the select() call

[pmichelmp3]

I modified my cron job to run an lsof on the faulty process

I just got another hang

the last strace line says:
ioctl(12, 0x40046445, 0x7fffb6d5a170) = -1 EINTR (Interrupted system call)
I dont remember seeing the "Interrupted system call" before !
maybe it's my lucky day...

So the file handle is #12...

Here is my lsof:

keuphoria 19810 pmichel 0r CHR 1,3 0t0 2037 /dev/null
keuphoria 19810 pmichel 1w REG 8,4 10271 5767238 /home/pmichel/.xsession-errors
keuphoria 19810 pmichel 2w REG 8,4 10271 5767238 /home/pmichel/.xsession-errors
keuphoria 19810 pmichel 3u unix 0xffff880103182600 0t0 107002 socket
keuphoria 19810 pmichel 4r FIFO 0,7 0t0 107004 pipe
keuphoria 19810 pmichel 5r CHR 1,9 0t0 413 /dev/urandom
keuphoria 19810 pmichel 6w FIFO 0,7 0t0 107004 pipe
keuphoria 19810 pmichel 7r FIFO 0,7 0t0 107005 pipe
keuphoria 19810 pmichel 8w FIFO 0,7 0t0 107005 pipe
keuphoria 19810 pmichel 9r FIFO 0,7 0t0 106996 pipe
keuphoria 19810 pmichel 10w FIFO 0,7 0t0 106996 pipe
keuphoria 19810 pmichel 11u unix 0xffff8800d0898680 0t0 107008 socket
keuphoria 19810 pmichel 12u CHR 226,0 0t0 7675 /dev/dri/card0
keuphoria 19810 pmichel 13u CHR 226,0 0t0 7675 /dev/dri/card0

Which is the video card...

I have an Intel 965 GM, with 3D enabled
I'll check for a newer version...

...crossing my fingers...