'imp' documentation does not mention that lock is re-entrant

[djmitche]

BPO	1625509
Nosy	@akuchling
Files	1625509.patch: 1625509.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 = 'https://github.com/akuchling'
closed_at = <Date 2008-05-10.17:49:14.873>
created_at = <Date 2007-01-01.00:22:20.000>
labels = ['docs']
title = "'imp' documentation does not mention that lock is re-entrant"
updated_at = <Date 2008-05-10.17:49:14.866>
user = 'https://bugs.python.org/djmitche'

bugs.python.org fields:

activity = <Date 2008-05-10.17:49:14.866>
actor = 'akuchling'
assignee = 'akuchling'
closed = True
closed_date = <Date 2008-05-10.17:49:14.873>
closer = 'akuchling'
components = ['Documentation']
creation = <Date 2007-01-01.00:22:20.000>
creator = 'djmitche'
dependencies = []
files = ['10258']
hgrepos = []
issue_num = 1625509
keywords = ['patch']
message_count = 3.0
messages = ['61049', '66543', '66545']
nosy_count = 2.0
nosy_names = ['akuchling', 'djmitche']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1625509'
versions = ['Python 2.5']

[djmitche]

My reading of import.c shows that imp.{acquire,release}_lock operate in the fashion of a threading.RLock, rather than a threading.Lock. Of course, this makes sense for the use to which it's put, but it would be great to have that mentioned explicitly in the documentation. Suggestion (stolen from threading documentation):

acquire_lock()
Acquires the interpreter's import lock for the current thread. This lock should be used by import hooks to ensure thread-safety when importing modules. 

Once a thread has acquired the import lock, the same thread may acquire it again without blocking; the thread must release it once for each time it has acquired it.

On platforms without threads, this function does nothing. New in version 2.3.

[djmitche]

Patch attached.

[akuchling]

Applied to trunk to r62996.