>Number: 149857
>Category: kern
>Synopsis: kqueue not reporting EOF under certain circumstances
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sat Aug 21 20:40:01 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator: Volodymyr Kostyrko
>Release: RELENG_8
>Organization:
>Environment:
FreeBSD limbo.lan 8.1-STABLE FreeBSD 8.1-STABLE #0 r211484M: Thu Aug 19
10:06:29 EEST 2010 [email protected]:/usr/obj/usr/src/sys/MINIMAL_8 i386
>Description:
kqueue ignores EOF event in some cases. I've tried to ping python people
thinking that this one can be python based but they don't think this happens in
python. In any case http://bugs.python.org/issue9591 is the place for this bug
in python roundup.
>How-To-Repeat:
Sorry for the python code, I'm bad at C.
Generally this program only eats everything what comes on stdin, logs any
kevents faced and exits on stream end. Two EOF cases are checked - when kqueue
returns 1 >> 15 (32768) or when we receive 0 bytes of data instead of value
given in kevent.
---------- test.py
#!/usr/bin/env python3.1
import select, sys
kq = select.kqueue()
assert kq.fileno() != -1, "Fatal error: can't initialise kqueue."
kq.control([select.kevent(sys.stdin, select.KQ_FILTER_READ, select.KQ_EV_ADD)],
0)
eof = False
while True:
kevs = kq.control(None, 1, None)
for kev in kevs:
print(kev.filter, kev.data, kev.flags, kev.ident, kev.fflags)
if kev.filter == select.KQ_FILTER_READ and kev.data > 0:
buffer = sys.stdin.read(kev.data)
if len(buffer) == 0:
print('eof')
eof = True
if kev.flags >> 15 == 1 or eof:
eof = True
kq.control([select.kevent(sys.stdin,
select.KQ_FILTER_READ, select.KQ_EV_DELETE)], 0)
if len(kevs) == 0 or eof:
break
---------- test.py
Now let's have some fun:
# cat test.py | ./test.py
-1 684 32768 0 0
#
This hangs:
# ./test.py < test.py
-1 684 0 0 0
<- We are hanging and waiting for other data.
I have tested that on RELENG_8 and RELENG_8_1 and results are the same.
>Fix:
None.
>Release-Note:
>Audit-Trail:
>Unformatted:
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