| msg14327 - (view) |
Author: Neal Norwitz (nnorwitz) *  |
Date: 2003-01-31 17:44 |
| test_mmap is failing on a flush while trying to do: Copy-on-write memory map data not written correctly The problem is that the mmap is opened with ACCESS_COPY. This translates to MAP_PRIVATE. On AIX, the msync man page says: "When the MS_SYNC and MAP_PRIVATE flags both are used, the msync subroutine returns an errno value of EINVAL." I'm not sure what the correct fix should be. |
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| msg14328 - (view) |
Author: Martin v. Löwis (loewis) * |
Date: 2003-03-04 07:00 |
| Logged In: YES user_id=21627 I think the test is somewhat bogus: It tries to check that modification to an ACCESS_COPY doesn't modify the underlying file, but assumes that .flush becomes a no-op, even though an exception is more reasonable (IMO; errors should never pass silently). So I see two options: Declare that .flush() always raises an exception (and modify implementations that don't produce an exception accordingly), or declare that aspect to be system-dependent, and modify the test (and the documentation) to expect and ignore an exception. Assigning to Tim, as he incorporated that feature into mmap. |
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| msg14329 - (view) |
Author: Tim Peters (tim.peters) * |
Date: 2003-04-28 19:55 |
| Logged In: YES user_id=31435 Sorry, I've had nothing to do with mmap beyond fixing bugs. The "access" feature was due to Jay Miller, although I believe I checked in his patch. Martin, I don't understand why you think it's reasonable for flush to complain here: the mmap is open for writing, so what's surprising about expecting to be able to flush after a write? Simply that there's no associated file, due to copy-on- write? Then user code would have to be acutely aware of how an mmap'ed object was opened, just to avoid nuisance complaints when they flush after writing. So that's a third alternative: alter the implementation to make mmap.flush() do nothing when an mmap object was opened as copy-on-write. |
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| msg14330 - (view) |
Author: Martin v. Löwis (loewis) * |
Date: 2003-05-03 10:09 |
| Logged In: YES user_id=21627 The documentation for flush says "Flushes changes made to the in-memory copy of a file back to disk." But it doesn't do that, and we all agree it shouldn't do that. So I would claim that it is an error to use .flush on an mmap object that was opened in ACCESS_COPY. This is like trying to write to a file that was opened for reading only: one *could* declare that the write just does nothing, but it helps the developer more if you get an exception, because the code is likely wrong (i.e. not following the likely intentions of the author). |
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| msg14331 - (view) |
Author: Tim Peters (tim.peters) * |
Date: 2003-05-06 20:00 |
| Logged In: YES user_id=31435 Hmm. I suspect the flush docs() are too strong (does flush really promise to materialize bytes *on disk*? it doesn't for other Python file objects, you also need os.fsync() for that). Your point is well taken, though, and whatever flush() does normally do, it's not going to do it for a copy-on-write mmap. So fine by me if we declare that attempting to flush() a copy- on-write mmap raises an exception. |
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| msg14332 - (view) |
Author: Richard Wheeler (wheelrl) |
Date: 2004-01-07 21:57 |
| Logged In: YES user_id=249546 I am getting the same error on AIX 5.2 with Python 2.3.3 release. What can I do to get around the test error and verify the mmap is working? |
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| msg14333 - (view) |
Author: Neal Norwitz (nnorwitz) * |
Date: 2004-01-07 22:06 |
| Logged In: YES user_id=33168 run the test with the -v flag: ./python ./Lib/test/regrtest.py -v test_mmap I think only everything should be fine up to copy-on-write tests. Here's what a good run looks like: [neal@epoch c3]$ ./python ./Lib/test/regrtest.py -v test_mmap test_mmap <type 'mmap.mmap'> Position of foo: 1.0 pages Length of file: 2.0 pages Contents of byte 0: '\x00' Contents of first 3 bytes: '\x00\x00\x00' Modifying file's content... Contents of byte 0: '3' Contents of first 3 bytes: '3\x00\x00' Contents of second page: '\x00foobar\x00' Regex match on mmap (page start, length of match): 1.0 6 Seek to zeroth byte Seek to 42nd byte Seek to last byte Try to seek to negative position... Try to seek beyond end of mmap... Try to seek to negative position... Attempting resize() Creating 10 byte test data file. Opening mmap with access=ACCESS_READ Ensuring that readonly mmap can't be slice assigned. Ensuring that readonly mmap can't be item assigned. Ensuring that readonly mmap can't be write() to. Ensuring that readonly mmap can't be write_byte() to. Ensuring that readonly mmap can't be resized. Opening mmap with size too big Opening mmap with access=ACCESS_WRITE Modifying write-through memory map. Opening mmap with access=ACCESS_COPY Modifying copy-on-write memory map. Ensuring copy-on-write maps cannot be resized. Ensuring invalid access parameter raises exception. Test passed 1 test OK. |
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| msg14334 - (view) |
Author: Mark D. Roth (mdr0) |
Date: 2004-03-10 17:14 |
| Logged In: YES user_id=994239 I'm running into this problem under both AIX 4.3.3 and 5.1. Is this something that's going to affect python if I put it into production, or is it "safe" to ignore it? |
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| msg14335 - (view) |
Author: Neal Norwitz (nnorwitz) * |
Date: 2004-03-11 18:59 |
| Logged In: YES user_id=33168 Mark, the 3 bugs you commented on (this one, 713169, and 678264) are all test errors AFAIK. It should be safe to ignore them. They are in extension modules that are not used by many people. |
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| msg81716 - (view) |
Author: Daniel Diniz (ajaksu2) *  |
Date: 2009-02-12 03:28 |
| Is this concern still valid? |
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| msg114215 - (view) |
Author: Mark Lawrence (BreamoreBoy) * |
Date: 2010-08-18 12:49 |
| Closed as no response to . |
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| msg117054 - (view) |
Author: Sébastien Sablé (sable) |
Date: 2010-09-21 14:47 |
| I would like to reopen this issue as it is still occurring in py3k on AIX 5.3 and 6.1: Re-running test test_mmap in verbose mode test_access_parameter (test.test_mmap.MmapTests) ... ERROR test_anonymous (test.test_mmap.MmapTests) ... ok test_bad_file_desc (test.test_mmap.MmapTests) ... ok test_basic (test.test_mmap.MmapTests) ... ok test_context_manager (test.test_mmap.MmapTests) ... ok test_context_manager_exception (test.test_mmap.MmapTests) ... ok test_double_close (test.test_mmap.MmapTests) ... ok test_entire_file (test.test_mmap.MmapTests) ... ok test_error (test.test_mmap.MmapTests) ... ok test_extended_getslice (test.test_mmap.MmapTests) ... ok test_extended_set_del_slice (test.test_mmap.MmapTests) ... ok test_find_end (test.test_mmap.MmapTests) ... ok test_io_methods (test.test_mmap.MmapTests) ... ok test_move (test.test_mmap.MmapTests) ... ok test_offset (test.test_mmap.MmapTests) ... ok test_prot_readonly (test.test_mmap.MmapTests) ... ok test_rfind (test.test_mmap.MmapTests) ... ok test_subclass (test.test_mmap.MmapTests) ... ok test_tougher_find (test.test_mmap.MmapTests) ... ok ====================================================================== ERROR: test_access_parameter (test.test_mmap.MmapTests) ---------------------------------------------------------------------- Traceback (most recent call last): File "/san_u02/home/recette/buildbot/buildbot-aix5/py3k-aix5-xlc/build/Lib/test/test_mmap.py", line 219, in test_access_parameter m.flush() mmap.error: [Errno 22] Invalid argument ---------------------------------------------------------------------- Ran 19 tests in 0.216s FAILED (errors=1) Should flush be modified to do nothing in this case or should the unit test be updated? thanks |
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| msg117070 - (view) |
Author: Martin v. Löwis (loewis) * |
Date: 2010-09-21 15:28 |
| > Should flush be modified to do nothing in this case or should the unit test be updated? Tim is suggesting that flush should indeed become a noop. Since nobody else speaking in favor of it being an error, I guess this is the way to go: flush, on an ACCESS_COPY file, does nothing, and the test is fine as it stands. |
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| msg117073 - (view) |
Author: Antoine Pitrou (pitrou) * |
Date: 2010-09-21 15:43 |
| Interestingly, the matter was discussed on another issue, #2643. I also agree that ideally flush() should become a no-op (only in 3.2, since it would break compatibility). But then we should also expose a separate sync() method with the current behaviour. |
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| msg117075 - (view) |
Author: Martin v. Löwis (loewis) * |
Date: 2010-09-21 15:53 |
| > Interestingly, the matter was discussed on another issue, #2643. I > also agree that ideally flush() should become a no-op (only in 3.2, > since it would break compatibility). But then we should also expose a > separate sync() method with the current behaviour. I think you misunderstand. I'm not proposing that flush should become a noop entirely - only for ACCESS_COPY mappings. |
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| msg117081 - (view) |
Author: Sébastien Sablé (sable) |
Date: 2010-09-21 16:36 |
| Would that patch be OK? It solves the test_mmap on AIX. |
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| msg117084 - (view) |
Author: Martin v. Löwis (loewis) * |
Date: 2010-09-21 17:16 |
| Looks fine to me. |
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| msg117129 - (view) |
Author: Sébastien Sablé (sable) |
Date: 2010-09-22 09:04 |
| After Antoine commit concerning , here is a new patch (just removing the changes in close). Could you commit it? |
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| msg118993 - (view) |
Author: R. David Murray (r.david.murray) * |
Date: 2010-10-18 01:15 |
| Committed to py3k in r85678. If I'm reading this string correctly, I believe this can (and should be) be backported. Am I correct? |
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| msg119002 - (view) |
Author: Sébastien Sablé (sable) |
Date: 2010-10-18 10:25 |
| I also believe this patch should be backported. If the is not backported, then the patch to apply should be "patch_flush_mmap.diff" instead of "patch_mmap_flush_updated.diff" |
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| msg123764 - (view) |
Author: R. David Murray (r.david.murray) * |
Date: 2010-12-11 02:13 |
| Committed the patch_flush_mmap patch to 3.1 in r87163 and 2.7 in r87164. |
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