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mmap.flush() issue msync() even if mapping was created with prot=mmap.PROT_READ only #55076

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socketpair mannequin opened this issue Jan 8, 2011 · 7 comments
Closed

mmap.flush() issue msync() even if mapping was created with prot=mmap.PROT_READ only #55076

socketpair mannequin opened this issue Jan 8, 2011 · 7 comments

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@socketpair
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Mannequin

socketpair mannequin commented Jan 8, 2011

BPO 10867
Nosy @bitdancer, @socketpair

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 2011-02-21.05:41:19.216>
created_at = <Date 2011-01-08.12:20:25.991>
labels = []
title = 'mmap.flush() issue msync() even if mapping was created with  prot=mmap.PROT_READ only'
updated_at = <Date 2011-02-21.05:41:19.216>
user = 'https://github.com/socketpair'

bugs.python.org fields:

activity = <Date 2011-02-21.05:41:19.216>
actor = 'socketpair'
assignee = 'none'
closed = True
closed_date = <Date 2011-02-21.05:41:19.216>
closer = 'socketpair'
components = []
creation = <Date 2011-01-08.12:20:25.991>
creator = 'socketpair'
dependencies = []
files = []
hgrepos = []
issue_num = 10867
keywords = []
message_count = 7.0
messages = ['125780', '125781', '125782', '125785', '125790', '125798', '125803']
nosy_count = 3.0
nosy_names = ['r.david.murray', 'neologix', 'socketpair']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue10867'
versions = []
@socketpair
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Mannequin Author

socketpair mannequin commented Jan 8, 2011

python mmap objects issue msync() in destructor even if mapping was created with prot=mmap.PROT_READ only

@socketpair
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Mannequin Author

socketpair mannequin commented Jan 8, 2011

Soory, this is dup of bpo-2643

@socketpair
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Mannequin Author

socketpair mannequin commented Jan 8, 2011

i'm crazy today. sorry twice. this is not dup of 2643 :(

@neologix
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Mannequin

neologix mannequin commented Jan 8, 2011

python mmap objects issue msync() in destructor even if mapping was created with prot=mmap.PROT_READ only

Actually, the call to msync(2) from destructor has been removed altogether in py3k. See http://bugs.python.org/issue2643.

The patch (one line) might be worth backporting, though.

@bitdancer
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Antoine didn't want to backport that patch. Does the fix applied in bpo-678250 address this?

@socketpair
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socketpair mannequin commented Jan 8, 2011

I have changed title of the bug. This is more precisely describe the problem.

In my code, I do mmap.close(), so msync does not called.

Generally, calling msync() on read-only mapping is not needed at all. And meven more, calling msync() on memory-mapped USB-camera will lead to EIO errno

I think, that flush() should be no-op if mapping is read-only.

@socketpair socketpair mannequin changed the title python mmap objects issue msync() in destructor even if mapping was created with prot=mmap.PROT_READ only mmap.flush() issue msync() even if mapping was created with prot=mmap.PROT_READ only Jan 8, 2011
@neologix
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neologix mannequin commented Jan 8, 2011

have changed title of the bug. This is more precisely describe the problem

Yes, its's not quite the same problem.

I think, that flush() should be no-op if mapping is read-only.

This has already be done for py3k. See http://svn.python.org/view/python/branches/py3k/Modules/mmapmodule.c?r1=84950&r2=85678

Note that you shouldn't be calling flush in the first place...

@socketpair socketpair mannequin closed this as completed Feb 21, 2011
@ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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