gevent.signal – Cooperative implementation of special cases of signal.signal()¶Cooperative implementation of special cases of signal.signal().
This module is designed to work with libev’s child watchers, as used
by default in gevent.os.fork() Note that each SIGCHLD
handler will be run in a new greenlet when the signal is delivered
(just like gevent.hub.signal)
The implementations in this module are only monkey patched if
gevent.os.waitpid() is being used (the default) and if
signal.SIGCHLD is available; see gevent.os.fork() for
information on configuring this not to be the case for advanced uses.
New in version 1.1b4.
Changed in version 1.5a4: Previously there was a backwards compatibility alias
gevent.signal, introduced in 1.1b4, that partly shadowed this
module, confusing humans and static analysis tools alike. That alias
has been removed. (See gevent.signal_handler.)
Exactly the same as signal.getsignal() except where
signal.SIGCHLD is concerned.
For signal.SIGCHLD, this cooperates with signal()
to provide consistent answers.
Exactly the same as signal.signal() except where
signal.SIGCHLD is concerned.
Note
A signal.SIGCHLD handler installed with this function
will only be triggered for children that are forked using
gevent.os.fork() (gevent.os.fork_and_watch());
children forked before monkey patching, or otherwise by the raw
os.fork(), will not trigger the handler installed by this
function. (It’s unlikely that a SIGCHLD handler installed with
the builtin signal.signal() would be triggered either;
libev typically overwrites such a handler at the C level. At
the very least, it’s full of race conditions.)
Note
Use of SIG_IGN and SIG_DFL may also have race conditions
with libev child watchers and the gevent.subprocess module.
Changed in version 1.2a1: If SIG_IGN or SIG_DFL are used to ignore SIGCHLD, a
future use of gevent.subprocess and libev child watchers
will once again work. However, on Python 2, use of os.popen
will fail.
Changed in version 1.1rc2: Allow using SIG_IGN and SIG_DFL to reset and ignore SIGCHLD.
However, this allows the possibility of a race condition if gevent.subprocess
had already been used.
Next page: gevent.subprocess – Cooperative subprocess module