open - resource temporarily unavailable

["Andrew P. Cherepenko" <A.P.Cherepenko@inp.nsk.su>]

Hello list,
  'open()' for creating file sometimes returns an error:
    couldn't open "myfile.txt": resource temporarily unavailable
    either in background process or interactively (ex: in Emacs when 
trying to save a file).

system: Debian 8.5
with kernel: linux-image-3.16.0-4-amd64
and systemd 215-17+deb8u4

Is that concerned with some imposed limits on the kernel resources ?

Following comprehensible suggestions about checking/changing such limits 
from here:
http://unix.stackexchange.com/questions/253903/creating-threads-fails-with-resource-temporarily-\
unavailable-with-4-3-kernel

I checked my circumstances.

me:~$ cat /proc/sys/kernel/threads-max
96126

me:~$ ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 48063
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 65536
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 32768
cpu time               (seconds, -t) unlimited
max user processes              (-u) 48063
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

me:~$ ls -1d /proc/*/task/* | wc -l
618

I thought the most important - the limit on open files:
me:~$ ulimit -n
65536

But in use there are:
jeder@mhfpklytstime:~$ lsof | wc -l
26117

So those seemingly reasonable suggestions gave me nothing.
It is quite upsetting too that
  neither the journal nor /var/log/syslog even mentioned the errors.

Am I missing something basic ?


Thanks,
  Andrey