multiprocessing.util._eintr_retry doen't recalculate timeouts

@pitrou

BPO	12338
Nosy	@pitrou, @vstinner
Files	mp_remove_eintr_retry.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2012-05-25.20:15:26.574>
created_at = <Date 2011-06-15.13:24:28.294>
labels = ['type-bug']
title = "multiprocessing.util._eintr_retry doen't recalculate timeouts"
updated_at = <Date 2012-05-25.20:15:26.572>
user = 'https://bugs.python.org/sbt'

bugs.python.org fields:

activity = <Date 2012-05-25.20:15:26.572>
actor = 'sbt'
assignee = 'none'
closed = True
closed_date = <Date 2012-05-25.20:15:26.574>
closer = 'sbt'
components = []
creation = <Date 2011-06-15.13:24:28.294>
creator = 'sbt'
dependencies = []
files = ['24888']
hgrepos = []
issue_num = 12338
keywords = ['patch']
message_count = 8.0
messages = ['138364', '138674', '156035', '156088', '157819', '157820', '157821', '161619']
nosy_count = 3.0
nosy_names = ['pitrou', 'vstinner', 'sbt']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue12338'
versions = ['Python 3.3']

multiprocessing.util._eintr_retry is only used to wrap select.select, but it fails to recalculate timeouts.

Also, it will never retry the function it wraps because of a missing "import errno".

I think it would be better to just implement the retrying version of select directly.

subprocess._communicate_with_select() retries select.select() on EINTR: it recomputes timeout before each call.

while self._read_set or self._write_set:
    timeout = self._remaining_time(endtime)
    if timeout is not None and timeout < 0:
        raise TimeoutExpired(self.args, orig_timeout)
    try:
        (rlist, wlist, xlist) = \
            select.select(self._read_set, self._write_set, [],
                          timeout)
    except select.error as e:
        if e.args[0] == errno.EINTR:
            continue
        raise
    ...

It has a similar code for select.poll().

asyncore.poll() handles EINTR: it just returns.

I think it would be better to just implement the retrying version
of select directly.

It would be nice to share more code between subprocess and multiprocessing, but I don't know where such code should be moved. Create a new module just for one function is stupid. Handling EINTR is a common problem when managing subprocesses.

subprocess has a _eintr_retry_call() function.

multiprocessing has a @_eintr_retry decorator handling supporting more error types (use except (EnvironmentError, select.error):).

_eintr_retry is currently unused. The attached patch removes it.

If it is retained then we should at least add a warning that it does not recalculate timeouts.

_eintr_retry is currently unused.

AFAICT it's still used in forking.py.

SocketServer has been changed to restart select() on EINTR, but it doesn't recompute the timeout.

SocketServer has been changed to restart select() on EINTR,
but it doesn't recompute the timeout.

See issue bpo-7978.

Note that socketserver's timeout is not really important: it's just used for a polling loop, with a default of 0.5 seconds.

_eintr_retry was removed by 99ef4501205b.

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multiprocessing.util._eintr_retry doen't recalculate timeouts #56547

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multiprocessing.util._eintr_retry doen't recalculate timeouts #56547

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sbt commented on Jun 15, 2011

vstinner commented on Jun 19, 2011

sbt commented on Mar 16, 2012

pitrou commented on Mar 16, 2012

vstinner commented on Apr 8, 2012

vstinner commented on Apr 8, 2012

pitrou commented on Apr 8, 2012

sbt commented on May 25, 2012

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