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[3.6] bpo-30807: signal.setitimer() may disable the timer by mistake (GH-2493) #2497

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Merged
pitrou merged 1 commit into from
Jun 30, 2017
Merged

[3.6] bpo-30807: signal.setitimer() may disable the timer by mistake (GH-2493) #2497

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9 changes: 9 additions & 0 deletions Lib/test/test_signal.py
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Original file line number Diff line number Diff line change
Expand Up @@ -611,6 +611,15 @@ def test_itimer_prof(self):
# and the handler should have been called
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):
"""
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6 changes: 6 additions & 0 deletions Misc/NEWS.d/next/Library/2017-06-29-22-04-44.bpo-30807.sLtjY-.rst
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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 changes: 4 additions & 0 deletions Modules/signalmodule.c
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Expand Up @@ -139,6 +139,10 @@ timeval_from_double(double d, struct timeval *tv)
{
tv->tv_sec = floor(d);
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)
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