[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[Eryk Sun]

Eryk Sun  added the comment:

> Given that this requirement is not universal and because a leading 
> slash controls other behaviors on platforms like Windows

Forward slash has no special meaning anywhere in the names of NT objects, such 
as memory Section objects (aka file-mapping objects) and registry Key objects. 
Only the file API translates forward slash to backslash, and that's only 
implemented for the sake of DOS compatibility in a few core functions that 
normalize and translate DOS paths.

Maybe you're thinking of the "Global\\" and "Session\\" prefixes for named 
kernel objects, which require a backslash since the name is really a 
handle-relative NT path. The session's object directory contains object 
symbolic links named "Global" and "Session". A name such as "Global\spam" 
resolves to "spam" in the global object directory, but "Global/spam", with 
forward slash, is just a regular name in the local directory.

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nosy: +eryksun

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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[STINNER Victor]

STINNER Victor  added the comment:

FYI the test also failed on AMD64 FreeBSD 10-STABLE Non-Debug 3.x:
https://buildbot.python.org/all/#/builders/167/builds/600

I will keep on eye on this buildbot worker as well ;-)

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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[Davin Potts]

Davin Potts  added the comment:

Closing.

Thank you Giampaolo for jumping in so quickly to review!

Thank you Victor for catching this on the buildbot.  Though what is this talk 
of "_if_ the color changes"? ;)

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resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[Davin Potts]

Davin Potts  added the comment:


New changeset aadef2b41600cb6a4f845cdc4cea001c916d8745 by Davin Potts in branch 
'master':
bpo-36102: Prepend slash to all POSIX shared memory block names (#12036)
https://github.com/python/cpython/commit/aadef2b41600cb6a4f845cdc4cea001c916d8745


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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[Rohit travels and tours]

Change by Rohit travels and tours :


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type:  -> resource usage

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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[STINNER Victor]

STINNER Victor  added the comment:

Apply the patch, we will see if the buildbot color changes :-)

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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[Davin Potts]

Change by Davin Potts :


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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[Davin Potts]

Davin Potts  added the comment:

I have locally tested GH-12036 on all 5 of the aforementioned OSes and all are 
made happy by the patch.

Victor:  If we want to go ahead and apply this patch right away to hopefully 
make the FreeBSD buildbot go green, the nature of this change is sufficiently 
small that it will still be easy to change during the alpha period.

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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[Davin Potts]

Change by Davin Potts :


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keywords: +patch
pull_requests: +12065
stage:  -> patch review

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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[Davin Potts]

Davin Potts  added the comment:

In local testing, I found the following systems to impose the leading slash as 
a requirement for simply creating a shared memory block:
* NetBSD 8.0
* FreeBSD 12.x
* TrueOS 18.12 (the OS formerly known as PC-BSD)

I found the following systems to have no required leading slash and all tests 
currently pass without modification:
* OpenBSD 6.4
* DragonflyBSD 5.4

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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[Davin Potts]

Davin Potts  added the comment:

Though apparently undocumented on FreeBSD, their implementation of shm_open 
differs from others in the following way:  all names for shared memory blocks 
*must* begin with a slash.  This requirement does not exist on OpenBSD.

According to its man page on shm_open, FreeBSD does at least communicate the 
following non-standard, additional requirement:
Two processes opening the same path
are guaranteed to access the same shared memory object if and only if
path begins with a slash (`/') character.


Given that this requirement is not universal and because a leading slash 
controls other behaviors on platforms like Windows, it would be confusing to 
make a leading slash a universal requirement.

Likewise, requiring users on FreeBSD to be aware of this nuance would be 
contrary to the goals of the SharedMemory class.


I will prepare a patch to prepend a leading slash onto the requested shared 
memory block name and detect the need for it.

I have verified that this does solve the problem on FreeBSD and that all tests 
then pass.  I will test NetBSD and DragonflyBSD to see if they also impose 
FreeBSD's undocumented requirement.

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[issue36102] TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x

[STINNER Victor]

New submission from STINNER Victor :

TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x:

* The tests should be skipped on this buildbot worker
* Or the feature should be fixed on FreeBSD

https://buildbot.python.org/all/#/builders/168/builds/617

Example:

ERROR: test_shared_memory_ShareableList_basics 
(test.test_multiprocessing_forkserver.WithProcessesTestSharedMemory)
--
Traceback (most recent call last):
  File 
"/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/_test_multiprocessing.py",
 line 3770, in test_shared_memory_ShareableList_basics
sl = shared_memory.ShareableList(
  File 
"/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/multiprocessing/shared_memory.py",
 line 305, in __init__
self.shm = SharedMemory(name, create=True, size=requested_size)
  File 
"/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/multiprocessing/shared_memory.py",
 line 88, in __init__
self._fd = _posixshmem.shm_open(
OSError: [Errno 22] Invalid argument: 'psm_f66c2bc7b9'

Failures:

ERROR: test_shared_memory_ShareableList_basics 
(test.test_multiprocessing_forkserver.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_ShareableList_pickling 
(test.test_multiprocessing_forkserver.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_SharedMemoryManager_basics 
(test.test_multiprocessing_forkserver.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_across_processes 
(test.test_multiprocessing_forkserver.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_basics 
(test.test_multiprocessing_forkserver.WithProcessesTestSharedMemory)

ERROR: test_shared_memory_ShareableList_basics 
(test.test_multiprocessing_fork.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_ShareableList_pickling 
(test.test_multiprocessing_fork.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_SharedMemoryManager_basics 
(test.test_multiprocessing_fork.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_across_processes 
(test.test_multiprocessing_fork.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_basics 
(test.test_multiprocessing_fork.WithProcessesTestSharedMemory)

ERROR: test_shared_memory_ShareableList_basics 
(test.test_multiprocessing_spawn.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_ShareableList_pickling 
(test.test_multiprocessing_spawn.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_SharedMemoryManager_basics 
(test.test_multiprocessing_spawn.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_across_processes 
(test.test_multiprocessing_spawn.WithProcessesTestSharedMemory)
ERROR: test_shared_memory_basics 
(test.test_multiprocessing_spawn.WithProcessesTestSharedMemory)

--
components: Tests
messages: 336503
nosy: davin, giampaolo.rodola, pitrou, vstinner
priority: normal
severity: normal
status: open
title: TestSharedMemory fails on AMD64 FreeBSD CURRENT Shared 3.x
versions: Python 3.8

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