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Issue #8407: The signal handler writes the signal number as a single byte

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instead of a nul byte into the wakeup file descriptor. So it is possible to
wait more than one signal and know which signals were raised.
This commit is contained in:
Victor Stinner 2011-05-08 02:03:15 +02:00
parent b3e7219abf
commit d49b1f14de
5 changed files with 35 additions and 5 deletions
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10
Doc/library/signal.rst
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@ -262,13 +262,17 @@ The :mod:`signal` module defines the following functions:
.. function:: set_wakeup_fd(fd)
Set the wakeup fd to *fd*. When a signal is received, a ``'\0'`` byte is
written to the fd. This can be used by a library to wakeup a poll or select
call, allowing the signal to be fully processed.
Set the wakeup file descriptor to *fd*. When a signal is received, the
signal number is written as a single byte into the fd. This can be used by
a library to wakeup a poll or select call, allowing the signal to be fully
processed.
The old wakeup fd is returned. *fd* must be non-blocking. It is up to the
library to remove any bytes before calling poll or select again.
Use for example ``struct.unpack('%uB' % len(data), data)`` to decode the
signal numbers list.
When threads are enabled, this function can only be called from the main thread;
attempting to call it from other threads will cause a :exc:`ValueError`
exception to be raised.