From f70e1ca0fc30426d12aa8fc6684764ee11a66777 Mon Sep 17 00:00:00 2001 From: Victor Stinner Date: Mon, 30 Mar 2015 21:16:11 +0200 Subject: Issue #23485: select.select() is now retried automatically with the recomputed timeout when interrupted by a signal, except if the signal handler raises an exception. This change is part of the PEP 475. The asyncore and selectors module doesn't catch the InterruptedError exception anymore when calling select.select(), since this function should not raise InterruptedError anymore. --- Doc/library/errno.rst | 5 +++- Doc/library/exceptions.rst | 7 ++++- Doc/library/select.rst | 7 +++++ Doc/whatsnew/3.5.rst | 14 +++++----- Lib/asyncore.py | 5 +--- Lib/selectors.py | 5 +--- Lib/test/eintrdata/eintr_tester.py | 16 +++++++++++- Misc/NEWS | 4 +++ Modules/selectmodule.c | 53 ++++++++++++++++++++++++++++---------- 9 files changed, 85 insertions(+), 31 deletions(-) diff --git a/Doc/library/errno.rst b/Doc/library/errno.rst index d2163b6..22a5cbc 100644 --- a/Doc/library/errno.rst +++ b/Doc/library/errno.rst @@ -41,7 +41,10 @@ defined by the module. The specific list of defined symbols is available as .. data:: EINTR - Interrupted system call + Interrupted system call. + + .. seealso:: + This error is mapped to the exception :exc:`InterruptedError`. .. data:: EIO diff --git a/Doc/library/exceptions.rst b/Doc/library/exceptions.rst index 271a5c8..bddd0ed 100644 --- a/Doc/library/exceptions.rst +++ b/Doc/library/exceptions.rst @@ -536,7 +536,12 @@ depending on the system error code. .. exception:: InterruptedError Raised when a system call is interrupted by an incoming signal. - Corresponds to :c:data:`errno` ``EINTR``. + Corresponds to :c:data:`errno` :py:data:`~errno.EINTR`. + + .. versionchanged:: 3.5 + Python now retries system calls when a syscall is interrupted by a + signal, except if the signal handler raises an exception (see :pep:`475` + for the rationale), instead of raising :exc:`InterruptedError`. .. exception:: IsADirectoryError diff --git a/Doc/library/select.rst b/Doc/library/select.rst index 5334af8..7fe09cb 100644 --- a/Doc/library/select.rst +++ b/Doc/library/select.rst @@ -145,6 +145,13 @@ The module defines the following: library, and does not handle file descriptors that don't originate from WinSock. + .. versionchanged:: 3.5 + The function is now retried with a recomputed timeout when interrupted by + a signal, except if the signal handler raises an exception (see + :pep:`475` for the rationale), instead of raising + :exc:`InterruptedError`. + + .. attribute:: PIPE_BUF The minimum number of bytes which can be written without blocking to a pipe diff --git a/Doc/whatsnew/3.5.rst b/Doc/whatsnew/3.5.rst index d33dfe8..3f70a94 100644 --- a/Doc/whatsnew/3.5.rst +++ b/Doc/whatsnew/3.5.rst @@ -173,9 +173,10 @@ PEP and implementation written by Ben Hoyt with the help of Victor Stinner. PEP 475: Retry system calls failing with EINTR ---------------------------------------------- -:pep:`475` adds support for automatic retry of system calls failing with EINTR: -this means that user code doesn't have to deal with EINTR or InterruptedError -manually, and should make it more robust against asynchronous signal reception. +:pep:`475` adds support for automatic retry of system calls failing with +:py:data:`~errno.EINTR`: this means that user code doesn't have to deal with +EINTR or :exc:`InterruptedError` manually, and should make it more robust +against asynchronous signal reception. .. seealso:: @@ -614,12 +615,13 @@ that may require changes to your code. Changes in the Python API ------------------------- -* :pep:`475`: the following functions are now retried when interrupted instead - of raising :exc:`InterruptedError` if the signal handler does not raise - an exception: +* :pep:`475`: Examples of functions which are now retried when interrupted + instead of raising :exc:`InterruptedError` if the signal handler does not + raise an exception: - :func:`os.open`, :func:`open` - :func:`os.read`, :func:`os.write` + - :func:`select.select` - :func:`time.sleep` * Before Python 3.5, a :class:`datetime.time` object was considered to be false diff --git a/Lib/asyncore.py b/Lib/asyncore.py index 68efd45..5578dda 100644 --- a/Lib/asyncore.py +++ b/Lib/asyncore.py @@ -141,10 +141,7 @@ def poll(timeout=0.0, map=None): time.sleep(timeout) return - try: - r, w, e = select.select(r, w, e, timeout) - except InterruptedError: - return + r, w, e = select.select(r, w, e, timeout) for fd in r: obj = map.get(fd) diff --git a/Lib/selectors.py b/Lib/selectors.py index 6d569c3..4f2a377 100644 --- a/Lib/selectors.py +++ b/Lib/selectors.py @@ -310,10 +310,7 @@ class SelectSelector(_BaseSelectorImpl): def select(self, timeout=None): timeout = None if timeout is None else max(timeout, 0) ready = [] - try: - r, w, _ = self._select(self._readers, self._writers, [], timeout) - except InterruptedError: - return ready + r, w, _ = self._select(self._readers, self._writers, [], timeout) r = set(r) w = set(w) for fd in r | w: diff --git a/Lib/test/eintrdata/eintr_tester.py b/Lib/test/eintrdata/eintr_tester.py index ba056fb..82cef83 100644 --- a/Lib/test/eintrdata/eintr_tester.py +++ b/Lib/test/eintrdata/eintr_tester.py @@ -10,6 +10,7 @@ sub-second periodicity (contrarily to signal()). import io import os +import select import signal import socket import time @@ -303,12 +304,25 @@ class SignalEINTRTest(EINTRBaseTest): self.assertGreaterEqual(dt, self.sleep_time) +@unittest.skipUnless(hasattr(signal, "setitimer"), "requires setitimer()") +class SelectEINTRTest(EINTRBaseTest): + """ EINTR tests for the select module. """ + + def test_select(self): + t0 = time.monotonic() + select.select([], [], [], self.sleep_time) + signal.alarm(0) + dt = time.monotonic() - t0 + self.assertGreaterEqual(dt, self.sleep_time) + + def test_main(): support.run_unittest( OSEINTRTest, SocketEINTRTest, TimeEINTRTest, - SignalEINTRTest) + SignalEINTRTest, + SelectEINTRTest) if __name__ == "__main__": diff --git a/Misc/NEWS b/Misc/NEWS index 36415588..b24ffb5 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -13,6 +13,10 @@ Core and Builtins Library ------- +- Issue #23485: select.select() is now retried automatically with the + recomputed timeout when interrupted by a signal, except if the signal handler + raises an exception. This change is part of the PEP 475. + - Issue #23752: When built from an existing file descriptor, io.FileIO() now only calls fstat() once. Before fstat() was called twice, which was not necessary. diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c index a852344..a6d6a83 100644 --- a/Modules/selectmodule.c +++ b/Modules/selectmodule.c @@ -193,29 +193,31 @@ select_select(PyObject *self, PyObject *args) #endif /* SELECT_USES_HEAP */ PyObject *ifdlist, *ofdlist, *efdlist; PyObject *ret = NULL; - PyObject *tout = Py_None; + PyObject *timeout_obj = Py_None; fd_set ifdset, ofdset, efdset; struct timeval tv, *tvp; int imax, omax, emax, max; int n; + _PyTime_t timeout, deadline = 0; /* convert arguments */ if (!PyArg_UnpackTuple(args, "select", 3, 4, - &ifdlist, &ofdlist, &efdlist, &tout)) + &ifdlist, &ofdlist, &efdlist, &timeout_obj)) return NULL; - if (tout == Py_None) - tvp = (struct timeval *)0; + if (timeout_obj == Py_None) + tvp = (struct timeval *)NULL; else { - _PyTime_t ts; - - if (_PyTime_FromSecondsObject(&ts, tout, _PyTime_ROUND_CEILING) < 0) { - PyErr_SetString(PyExc_TypeError, - "timeout must be a float or None"); + if (_PyTime_FromSecondsObject(&timeout, timeout_obj, + _PyTime_ROUND_CEILING) < 0) { + if (PyErr_ExceptionMatches(PyExc_TypeError)) { + PyErr_SetString(PyExc_TypeError, + "timeout must be a float or None"); + } return NULL; } - if (_PyTime_AsTimeval(ts, &tv, _PyTime_ROUND_CEILING) == -1) + if (_PyTime_AsTimeval(timeout, &tv, _PyTime_ROUND_CEILING) == -1) return NULL; if (tv.tv_sec < 0) { PyErr_SetString(PyExc_ValueError, "timeout must be non-negative"); @@ -224,7 +226,6 @@ select_select(PyObject *self, PyObject *args) tvp = &tv; } - #ifdef SELECT_USES_HEAP /* Allocate memory for the lists */ rfd2obj = PyMem_NEW(pylist, FD_SETSIZE + 1); @@ -237,6 +238,7 @@ select_select(PyObject *self, PyObject *args) return PyErr_NoMemory(); } #endif /* SELECT_USES_HEAP */ + /* Convert sequences to fd_sets, and get maximum fd number * propagates the Python exception set in seq2set() */ @@ -249,13 +251,36 @@ select_select(PyObject *self, PyObject *args) goto finally; if ((emax=seq2set(efdlist, &efdset, efd2obj)) < 0) goto finally; + max = imax; if (omax > max) max = omax; if (emax > max) max = emax; - Py_BEGIN_ALLOW_THREADS - n = select(max, &ifdset, &ofdset, &efdset, tvp); - Py_END_ALLOW_THREADS + if (tvp) + deadline = _PyTime_GetMonotonicClock() + timeout; + + do { + Py_BEGIN_ALLOW_THREADS + errno = 0; + n = select(max, &ifdset, &ofdset, &efdset, tvp); + Py_END_ALLOW_THREADS + + if (errno != EINTR) + break; + + /* select() was interrupted by a signal */ + if (PyErr_CheckSignals()) + goto finally; + + if (tvp) { + timeout = deadline - _PyTime_GetMonotonicClock(); + if (timeout < 0) { + n = 0; + break; + } + _PyTime_AsTimeval_noraise(timeout, &tv, _PyTime_ROUND_CEILING); + } + } while (1); #ifdef MS_WINDOWS if (n == SOCKET_ERROR) { -- cgit v0.12