This ignores CTRL-C on every platform I've tested:
python -c "import threading; threading.Event ().wait()"
^C^C^C^C
It looks to me like all signals are masked before entering wait(). Can
someone familiar with the internals explain and/or justify this
behavior? Thanks,
-Alan 3 3508
On Sat, May 17, 2008 at 2:49 PM, John Schroeder <js******@gmail .comwrote:
^C only kills the main thread. Use Control-Break to kill all threads.
>> python -c "import threading; threading.Event ().wait()" ^C^C^C^C
There's a single main thread here though. Or am I missing something?
alan schrieb:
This ignores CTRL-C on every platform I've tested:
python -c "import threading; threading.Event ().wait()"
^C^C^C^C
It looks to me like all signals are masked before entering wait(). Can
someone familiar with the internals explain and/or justify this
behavior? Thanks,
They aren't masked. Read the docs:
# Although Python signal handlers are called asynchronously as far as
the Python user is concerned, they can only occur between the ``atomic''
instructions of the Python interpreter. This means that signals arriving
during long calculations implemented purely in C (such as regular
expression matches on large bodies of text) may be delayed for an
arbitrary amount of time.
( http://docs.python.org/lib/module-signal.html)
Which is what is happening here - wait is implemented in C. So the
arriving signal is stored flagged in the interpreter so that the next
bytecode would be the signal-handler set - but the interpreter still
waits for the blocked call.
Diez
On May 18, 9:05 am, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:
alan schrieb:
This ignores CTRL-C on every platform I've tested:
python -c "import threading; threading.Event ().wait()"
^C^C^C^C
It looks to me like all signals are masked before entering wait(). Can
someone familiar with the internals explain and/or justify this
behavior? Thanks,
They aren't masked. Read the docs:
# Although Python signal handlers are called asynchronously as far as
the Python user is concerned, they can only occur between the ``atomic''
instructions of the Python interpreter. This means that signals arriving
during long calculations implemented purely in C (such as regular
expression matches on large bodies of text) may be delayed for an
arbitrary amount of time.
(http://docs.python.org/lib/module-signal.html)
Which is what is happening here - wait is implemented in C. So the
arriving signal is stored flagged in the interpreter so that the next
bytecode would be the signal-handler set - but the interpreter still
waits for the blocked call.
If a signal arrives while the thread is in a syscall it will usually
interrupt the syscall. Most code in the interpreter will see the
EINTR error code and check if we have a signal to process, which leads
to raising a KeyboardInterru pt exception. However, most thread
synchronization functions specified in POSIX are not interrupted by
signals, so the interpreter never has a chance do anything. Why would
we care anyway, as Python doesn't let you intentionally interrupt a
non-main thread? This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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