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Diffstat (limited to 'Doc/library/signal.rst')
| -rw-r--r-- | Doc/library/signal.rst | 165 |
1 files changed, 157 insertions, 8 deletions
diff --git a/Doc/library/signal.rst b/Doc/library/signal.rst index 698b1e7..4fc3fd6 100644 --- a/Doc/library/signal.rst +++ b/Doc/library/signal.rst @@ -13,9 +13,6 @@ rules for working with signals and their handlers: underlying implementation), with the exception of the handler for :const:`SIGCHLD`, which follows the underlying implementation. -* There is no way to "block" signals temporarily from critical sections (since - this is not supported by all Unix flavors). - * 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 @@ -119,6 +116,28 @@ The variables defined in the :mod:`signal` module are: in user and kernel space. SIGPROF is delivered upon expiration. +.. data:: SIG_BLOCK + + A possible value for the *how* parameter to :func:`pthread_sigmask` + indicating that signals are to be blocked. + + .. versionadded:: 3.3 + +.. data:: SIG_UNBLOCK + + A possible value for the *how* parameter to :func:`pthread_sigmask` + indicating that signals are to be unblocked. + + .. versionadded:: 3.3 + +.. data:: SIG_SETMASK + + A possible value for the *how* parameter to :func:`pthread_sigmask` + indicating that the signal mask is to be replaced. + + .. versionadded:: 3.3 + + The :mod:`signal` module defines one exception: .. exception:: ItimerError @@ -126,7 +145,11 @@ The :mod:`signal` module defines one exception: Raised to signal an error from the underlying :func:`setitimer` or :func:`getitimer` implementation. Expect this error if an invalid interval timer or a negative time is passed to :func:`setitimer`. - This error is a subtype of :exc:`IOError`. + This error is a subtype of :exc:`OSError`. + + .. versionadded:: 3.3 + This error used to be a subtype of :exc:`IOError`, which is now an + alias of :exc:`OSError`. The :mod:`signal` module defines the following functions: @@ -160,6 +183,60 @@ The :mod:`signal` module defines the following functions: will then be called. Returns nothing. Not on Windows. (See the Unix man page :manpage:`signal(2)`.) + See also :func:`sigwait`, :func:`sigwaitinfo`, :func:`sigtimedwait` and + :func:`sigpending`. + + +.. function:: pthread_kill(thread_id, signum) + + Send the signal *signum* to the thread *thread_id*, another thread in the same + process as the caller. The signal is asynchronously directed to thread. + + Use :func:`threading.get_ident()` or the :attr:`~threading.Thread.ident` + attribute of :attr:`threading.Thread` to get a 'thread identifier' for + *thread_id*. + + If *signum* is 0, then no signal is sent, but error checking is still + performed; this can be used to check if a thread is still running. + + Availability: Unix (see the man page :manpage:`pthread_kill(3)` for further + information). + + See also :func:`os.kill`. + + .. versionadded:: 3.3 + + +.. function:: pthread_sigmask(how, mask) + + Fetch and/or change the signal mask of the calling thread. The signal mask + is the set of signals whose delivery is currently blocked for the caller. + Return the old signal mask as a set of signals. + + The behavior of the call is dependent on the value of *how*, as follows. + + * :data:`SIG_BLOCK`: The set of blocked signals is the union of the current + set and the *mask* argument. + * :data:`SIG_UNBLOCK`: The signals in *mask* are removed from the current + set of blocked signals. It is permissible to attempt to unblock a + signal which is not blocked. + * :data:`SIG_SETMASK`: The set of blocked signals is set to the *mask* + argument. + + *mask* is a set of signal numbers (e.g. {:const:`signal.SIGINT`, + :const:`signal.SIGTERM`}). Use ``range(1, signal.NSIG)`` for a full mask + including all signals. + + For example, ``signal.pthread_sigmask(signal.SIG_BLOCK, [])`` reads the + signal mask of the calling thread. + + Availability: Unix. See the man page :manpage:`sigprocmask(3)` and + :manpage:`pthread_sigmask(3)` for further information. + + See also :func:`pause`, :func:`sigpending` and :func:`sigwait`. + + .. versionadded:: 3.3 + .. function:: setitimer(which, seconds[, interval]) @@ -189,13 +266,17 @@ 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. @@ -235,6 +316,74 @@ The :mod:`signal` module defines the following functions: :const:`SIGTERM`. A :exc:`ValueError` will be raised in any other case. +.. function:: sigpending() + + Examine the set of signals that are pending for delivery to the calling + thread (i.e., the signals which have been raised while blocked). Return the + set of the pending signals. + + Availability: Unix (see the man page :manpage:`sigpending(2)` for further + information). + + See also :func:`pause`, :func:`pthread_sigmask` and :func:`sigwait`. + + .. versionadded:: 3.3 + + +.. function:: sigwait(sigset) + + Suspend execution of the calling thread until the delivery of one of the + signals specified in the signal set *sigset*. The function accepts the signal + (removes it from the pending list of signals), and returns the signal number. + + Availability: Unix (see the man page :manpage:`sigwait(3)` for further + information). + + See also :func:`pause`, :func:`pthread_sigmask`, :func:`sigpending`, + :func:`sigwaitinfo` and :func:`sigtimedwait`. + + .. versionadded:: 3.3 + + +.. function:: sigwaitinfo(sigset) + + Suspend execution of the calling thread until the delivery of one of the + signals specified in the signal set *sigset*. The function accepts the + signal and removes it from the pending list of signals. If one of the + signals in *sigset* is already pending for the calling thread, the function + will return immediately with information about that signal. The signal + handler is not called for the delivered signal. The function raises an + :exc:`InterruptedError` if it is interrupted by a signal that is not in + *sigset*. + + The return value is an object representing the data contained in the + :c:type:`siginfo_t` structure, namely: :attr:`si_signo`, :attr:`si_code`, + :attr:`si_errno`, :attr:`si_pid`, :attr:`si_uid`, :attr:`si_status`, + :attr:`si_band`. + + Availability: Unix (see the man page :manpage:`sigwaitinfo(2)` for further + information). + + See also :func:`pause`, :func:`sigwait` and :func:`sigtimedwait`. + + .. versionadded:: 3.3 + + +.. function:: sigtimedwait(sigset, (timeout_sec, timeout_nsec)) + + Like :func:`sigtimedwait`, but takes a tuple of ``(seconds, nanoseconds)`` + as an additional argument specifying a timeout. If both *timeout_sec* and + *timeout_nsec* are specified as :const:`0`, a poll is performed. Returns + :const:`None` if a timeout occurs. + + Availability: Unix (see the man page :manpage:`sigtimedwait(2)` for further + information). + + See also :func:`pause`, :func:`sigwait` and :func:`sigwaitinfo`. + + .. versionadded:: 3.3 + + .. _signal-example: Example @@ -251,7 +400,7 @@ be sent, and the handler raises an exception. :: def handler(signum, frame): print('Signal handler called with signal', signum) - raise IOError("Couldn't open device!") + raise OSError("Couldn't open device!") # Set the signal handler and a 5-second alarm signal.signal(signal.SIGALRM, handler) |