<h2>Edit File - semaphore_tracker.py</h2><form method="POST" style="padding:20px">
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# On Unix we run a server process which keeps track of unlinked
# semaphores. The server ignores SIGINT and SIGTERM and reads from a
# pipe.  Every other process of the program has a copy of the writable
# end of the pipe, so we get EOF when all other processes have exited.
# Then the server process unlinks any remaining semaphore names.
#
# This is important because the system only supports a limited number
# of named semaphores, and they will not be automatically removed till
# the next reboot.  Without this semaphore tracker process, &quot;killall
# python&quot; would probably leave unlinked semaphores.
#

import os
import signal
import sys
import threading
import warnings
import _multiprocessing

from . import spawn
from . import util

__all__ = [&#039;ensure_running&#039;, &#039;register&#039;, &#039;unregister&#039;]


class SemaphoreTracker(object):

    def __init__(self):
        self._lock = threading.Lock()
        self._fd = None
        self._pid = None

    def getfd(self):
        self.ensure_running()
        return self._fd

    def ensure_running(self):
        &#039;&#039;&#039;Make sure that semaphore tracker process is running.

        This can be run from any process.  Usually a child process will use
        the semaphore created by its parent.&#039;&#039;&#039;
        with self._lock:
            if self._pid is not None:
                # semaphore tracker was launched before, is it still running?
                pid, status = os.waitpid(self._pid, os.WNOHANG)
                if not pid:
                    # =&gt; still alive
                    return
                # =&gt; dead, launch it again
                os.close(self._fd)
                self._fd = None
                self._pid = None

                warnings.warn(&#039;semaphore_tracker: process died unexpectedly, &#039;
                              &#039;relaunching.  Some semaphores might leak.&#039;)

            fds_to_pass = []
            try:
                fds_to_pass.append(sys.stderr.fileno())
            except Exception:
                pass
            cmd = &#039;from multiprocessing.semaphore_tracker import main;main(%d)&#039;
            r, w = os.pipe()
            try:
                fds_to_pass.append(r)
                # process will out live us, so no need to wait on pid
                exe = spawn.get_executable()
                args = [exe] + util._args_from_interpreter_flags()
                args += [&#039;-c&#039;, cmd % r]
                pid = util.spawnv_passfds(exe, args, fds_to_pass)
            except:
                os.close(w)
                raise
            else:
                self._fd = w
                self._pid = pid
            finally:
                os.close(r)

    def register(self, name):
        &#039;&#039;&#039;Register name of semaphore with semaphore tracker.&#039;&#039;&#039;
        self._send(&#039;REGISTER&#039;, name)

    def unregister(self, name):
        &#039;&#039;&#039;Unregister name of semaphore with semaphore tracker.&#039;&#039;&#039;
        self._send(&#039;UNREGISTER&#039;, name)

    def _send(self, cmd, name):
        self.ensure_running()
        msg = &#039;{0}:{1}\n&#039;.format(cmd, name).encode(&#039;ascii&#039;)
        if len(name) &gt; 512:
            # posix guarantees that writes to a pipe of less than PIPE_BUF
            # bytes are atomic, and that PIPE_BUF &gt;= 512
            raise ValueError(&#039;name too long&#039;)
        nbytes = os.write(self._fd, msg)
        assert nbytes == len(msg)


_semaphore_tracker = SemaphoreTracker()
ensure_running = _semaphore_tracker.ensure_running
register = _semaphore_tracker.register
unregister = _semaphore_tracker.unregister
getfd = _semaphore_tracker.getfd


def main(fd):
    &#039;&#039;&#039;Run semaphore tracker.&#039;&#039;&#039;
    # protect the process from ^C and &quot;killall python&quot; etc
    signal.signal(signal.SIGINT, signal.SIG_IGN)
    signal.signal(signal.SIGTERM, signal.SIG_IGN)

    for f in (sys.stdin, sys.stdout):
        try:
            f.close()
        except Exception:
            pass

    cache = set()
    try:
        # keep track of registered/unregistered semaphores
        with open(fd, &#039;rb&#039;) as f:
            for line in f:
                try:
                    cmd, name = line.strip().split(b&#039;:&#039;)
                    if cmd == b&#039;REGISTER&#039;:
                        cache.add(name)
                    elif cmd == b&#039;UNREGISTER&#039;:
                        cache.remove(name)
                    else:
                        raise RuntimeError(&#039;unrecognized command %r&#039; % cmd)
                except Exception:
                    try:
                        sys.excepthook(*sys.exc_info())
                    except:
                        pass
    finally:
        # all processes have terminated; cleanup any remaining semaphores
        if cache:
            try:
                warnings.warn(&#039;semaphore_tracker: There appear to be %d &#039;
                              &#039;leaked semaphores to clean up at shutdown&#039; %
                              len(cache))
            except Exception:
                pass
        for name in cache:
            # For some reason the process which created and registered this
            # semaphore has failed to unregister it. Presumably it has died.
            # We therefore unlink it.
            try:
                name = name.decode(&#039;ascii&#039;)
                try:
                    _multiprocessing.sem_unlink(name)
                except Exception as e:
                    warnings.warn(&#039;semaphore_tracker: %r: %s&#039; % (name, e))
            finally:
                pass
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