Re: Emacs Hangs on Filesystem Operations on Stale NFS

[Alexander Shukaev]

On 2018-06-11 13:59, Noam Postavsky wrote:
> On 11 June 2018 at 06:27, Alexander Shukaev
> <address@hidden> wrote:
>
> > Well, enough rant.  I think I have a proposal how to fix the issue, 
> > even
> > given the blocking nature of Emacs.  How about introducing a variable
> > `file-access-timeout' defaulting to `nil', which would reflect a
> > configurable timeout for all access operations (such as 
> > `file-readable-p')?
> > This would be achieved via `SIGALARM' in the C code, which would 
> > protect
> > every such operation.  For example,
>
> Does it work? According to some messages on the previous thread you
> referenced [1], NFS hangs happen in the kernel so a signal would not
> help.
>
> [1]: 
> https://lists.gnu.org/archive/html/help-gnu-emacs/2015-11/msg00266.html

Go ahead and try:

import os
import signal
import subprocess

class Alarm(Exception):
  pass

def alarm_handler(signum, frame):
  raise Alarm

path = '/mnt/<nfs>'

signal.signal(signal.SIGALRM, alarm_handler)
signal.alarm(3)
try:
  proc = subprocess.call('stat ' + path,
               shell=True,
               stderr=subprocess.PIPE,
               stdout=subprocess.PIPE)
  stdoutdata, stderrdata = proc.communicate()
  signal.alarm(0)
except Alarm:
  print "Timed out after 3 seconds..."