From: Victor Stinner <victor.stinner@gmail.com>
Date: Thu, 17 Jul 2014 20:45:42 +0000 (+0200)
Subject: (Merge 3.4) Python issue #21645, Tulip issue 192: Rewrite signal handling
X-Git-Tag: v3.5.0a1~1261
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=2fa2c3dfc5d9f0e61a9ffd37b5edeb04e8b8faeb;p=thirdparty%2FPython%2Fcpython.git

(Merge 3.4) Python issue #21645, Tulip issue 192: Rewrite signal handling

Since Python 3.3, the C signal handler writes the signal number into the wakeup
file descriptor and then schedules the Python call using Py_AddPendingCall().

asyncio uses the wakeup file descriptor to wake up the event loop, and relies
on Py_AddPendingCall() to schedule the final callback with call_soon().

If the C signal handler is called in a thread different than the thread of the
event loop, the loop is awaken but Py_AddPendingCall() was not called yet. In
this case, the event loop has nothing to do and go to sleep again.
Py_AddPendingCall() is called while the event loop is sleeping again and so the
final callback is not scheduled immediatly.

This patch changes how asyncio handles signals. Instead of relying on
Py_AddPendingCall() and the wakeup file descriptor, asyncio now only relies on
the wakeup file descriptor. asyncio reads signal numbers from the wakeup file
descriptor to call its signal handler.
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