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bpo-30807: signal.setitimer() may disable the timer by mistake (#2493)

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* bpo-30807: signal.setitimer() may disable the timer by mistake

* Add NEWS blurb
This commit is contained in:
Antoine Pitrou 2017-06-30 10:01:05 +02:00 • committed by GitHub
parent 42bc8beadd
commit 729780a810
3 changed files with 19 additions and 0 deletions
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9
Lib/test/test_signal.py
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@ -608,6 +608,15 @@ class ItimerTest(unittest.TestCase):
# and the handler should have been called # and the handler should have been called
self.assertEqual(self.hndl_called, True) self.assertEqual(self.hndl_called, True)
def test_setitimer_tiny(self):
# bpo-30807: C setitimer() takes a microsecond-resolution interval.
# Check that float -> timeval conversion doesn't round
# the interval down to zero, which would disable the timer.
self.itimer = signal.ITIMER_REAL
signal.setitimer(self.itimer, 1e-6)
time.sleep(1)
self.assertEqual(self.hndl_called, True)
class PendingSignalsTests(unittest.TestCase): class PendingSignalsTests(unittest.TestCase):
""" """

6
Misc/NEWS.d/next/Library/2017-06-29-22-04-44.bpo-30807.sLtjY-.rst Normal file
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@ -0,0 +1,6 @@
signal.setitimer() may disable the timer when passed a tiny value.
Tiny values (such as 1e-6) are valid non-zero values for setitimer(), which
is specified as taking microsecond-resolution intervals. However, on some
platform, our conversion routine could convert 1e-6 into a zero interval,
therefore disabling the timer instead of (re-)scheduling it.

4
Modules/signalmodule.c
View file

@ -139,6 +139,10 @@ timeval_from_double(double d, struct timeval *tv)
{ {
tv->tv_sec = floor(d); tv->tv_sec = floor(d);
tv->tv_usec = fmod(d, 1.0) * 1000000.0; tv->tv_usec = fmod(d, 1.0) * 1000000.0;
/* Don't disable the timer if the computation above rounds down to zero. */
if (d > 0.0 && tv->tv_sec == 0 && tv->tv_usec == 0) {
tv->tv_usec = 1;
}
} }
Py_LOCAL_INLINE(double) Py_LOCAL_INLINE(double)