Edit report at https://bugs.php.net/bug.php?id=63709&edit=1
ID: 63709
User updated by: eric dot saintetienne at gmail dot com
Reported by: eric dot saintetienne at gmail dot com
Summary: flock() doesn't trigger mandatory locks on linux
Status: Analyzed
Type: Bug
Package: Filesystem function related
Operating System: Linux
PHP Version: 5.3.19
Block user comment: N
Private report: N
New Comment:
You're right, dio is a plain inteface to the underlying C function hence exposing
real file descriptors (integers).
That's also what Python does: it exposes two different types of file objects:
standard file objects via the builtin open() and file descriptors via os.open()
Is that is feasible with php?
Previous Comments:
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[2012-12-07 08:48:41] aharvey@php.net
My worry there is that dio resources are (as I recall, anyway) completely distinct from normal file
resources, so you couldn't fopen() a file and then dio_fcntl() it: it's all or nothing.
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[2012-12-07 08:42:12] eric dot saintetienne at gmail dot com
A fifth option is to pull the "Direct IO" extension into the mainline.
http://pecl.php.net/package/dio
This extension already expose fcntl() as well as a few other low-level
POSIX routines, and have some amount of testing as it's in its fourth
version already (though it's said to be in beta state)
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[2012-12-07 03:24:16] laruence@php.net
I like 3 :)
change the behavior of flock will intruduce a visible bc break
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[2012-12-07 01:48:08] aharvey@php.net
The key difference between Python and PHP here is that Python always uses fcntl() internally,
whereas PHP will use flock() if it's available (which it obviously is on Linux) and will only
fall back to fcntl() if it's not. flock() will never create a mandatory lock, so the manual
page is wrong, which I'm pretty sure is my fault. Mea culpa.
We can probably fix this by switching to preferring fcntl() within our flock() function as Python
does, since that's actually the more useful behaviour, but that would be a (mild) BC break in
how flock() behaves in practice â although it would actually bring it into line with
what's documented.
The options I see are:
1. Change the behaviour of flock() as described above to prefer fcntl().
2. Add a new lockf() function, as suggested.
3. Just bite the bullet and expose fcntl() as a PHP function on POSIX platforms.
4. Do nothing and update the manual. :)
Does anyone have any thoughts? I'm happy to do the donkey work, but am not really sure on the
best way to proceed.
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[2012-12-06 14:19:38] eric dot saintetienne at gmail dot com
Note that dio_fcntl() of the "Direct IO" extension can successfully exclusively
lock the file, but this shouldn't be considered as a workaround as it's not always
possible to install extensions.
If flock() couldn't be modified for backward compatibility reasons, options could
be added to alter its behaviour, or a new call lockf() would be welcome too.
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