Hi internals,
while having had a closer look at https://bugs.php.net/78754, I
learned that OPcache's file_cache is prone to some configuration
changes, which may cause PHP segfaults (and maybe other malfunctions).
For instance, if Xdebug is enabled while a file is compiled, but later
disabled when executing that file, the process is segfaulting because
the cached file relies on user opcode handlers which are no longer
available without Xdebug loaded. I'm presenting Xdebug as example
because that likely caused the issues reported in that ticket, but
basically any extension can call zend_set_user_opcode_handler() to
install user opcode handlers, causing the same problems.
It should be mentioned that, to my knowledge, shared memory caches are
not affected by this (except for Windows), because re-attaching a
differently configured php instance isn't possible at all.
Anyhow, should we fix this (assuming a general fix would be possible),
or would that be rather a documentation issue, based on the assumption
that such configuration changes don't make sense in combination with
OPcache at all (IOW, if such changes are done, users should reset OPcache).
--
Christoph M. Becker
while having had a closer look at https://bugs.php.net/78754, I
learned that OPcache's file_cache is prone to some configuration
changes, which may cause PHP segfaults (and maybe other malfunctions).
For instance, if Xdebug is enabled while a file is compiled, but later
disabled when executing that file, the process is segfaulting because
the cached file relies on user opcode handlers which are no longer
available without Xdebug loaded. I'm presenting Xdebug as example
because that likely caused the issues reported in that ticket, but
basically any extension can call zend_set_user_opcode_handler() to
install user opcode handlers, causing the same problems.It should be mentioned that, to my knowledge, shared memory caches are
not affected by this (except for Windows), because re-attaching a
differently configured php instance isn't possible at all.Anyhow, should we fix this (assuming a general fix would be possible),
or would that be rather a documentation issue, based on the assumption
that such configuration changes don't make sense in combination with
OPcache at all (IOW, if such changes are done, users should reset OPcache)..
Any thoughts regarding this issue?
--
Christoph M. Becker
while having had a closer look at https://bugs.php.net/78754, I
learned that OPcache's file_cache is prone to some configuration
changes, which may cause PHP segfaults (and maybe other malfunctions).
For instance, if Xdebug is enabled while a file is compiled, but later
disabled when executing that file, the process is segfaulting because
the cached file relies on user opcode handlers which are no longer
available without Xdebug loaded. I'm presenting Xdebug as example
because that likely caused the issues reported in that ticket, but
basically any extension can call zend_set_user_opcode_handler() to
install user opcode handlers, causing the same problems.It should be mentioned that, to my knowledge, shared memory caches are
not affected by this (except for Windows), because re-attaching a
differently configured php instance isn't possible at all.Anyhow, should we fix this (assuming a general fix would be possible),
or would that be rather a documentation issue, based on the assumption
that such configuration changes don't make sense in combination with
OPcache at all (IOW, if such changes are done, users should reset OPcache)..Any thoughts regarding this issue?
Hi,
My knowledge of opcache is limited, so please forgive me if the
following is incomplete or incorrect. My impression is that the amount
of information that is used to compute the hash for the file cache
directory is a bit low. I see the PHP version go in, an internal API
version and some machine architecture related things.
I would have expected that much - if not all - of the output of
phpinfo() would be included in the hash for example. Better be safe than
sorry. Would that be a sane thing to do? Are there any reasons why this
is currently not done?
Thanks,
Dik Takken
while having had a closer look at https://bugs.php.net/78754, I
learned that OPcache's file_cache is prone to some configuration
changes, which may cause PHP segfaults (and maybe other malfunctions).
For instance, if Xdebug is enabled while a file is compiled, but later
disabled when executing that file, the process is segfaulting because
the cached file relies on user opcode handlers which are no longer
available without Xdebug loaded. I'm presenting Xdebug as example
because that likely caused the issues reported in that ticket, but
basically any extension can call zend_set_user_opcode_handler() to
install user opcode handlers, causing the same problems.It should be mentioned that, to my knowledge, shared memory caches are
not affected by this (except for Windows), because re-attaching a
differently configured php instance isn't possible at all.Anyhow, should we fix this (assuming a general fix would be possible),
or would that be rather a documentation issue, based on the assumption
that such configuration changes don't make sense in combination with
OPcache at all (IOW, if such changes are done, users should reset OPcache)..Any thoughts regarding this issue?
My knowledge of opcache is limited, so please forgive me if the
following is incomplete or incorrect. My impression is that the amount
of information that is used to compute the hash for the file cache
directory is a bit low. I see the PHP version go in, an internal API
version and some machine architecture related things.I would have expected that much - if not all - of the output of
phpinfo()would be included in the hash for example. Better be safe than
sorry. Would that be a sane thing to do? Are there any reasons why this
is currently not done?
Factoring in the complete PHP info can't work, since that also contains
some request specific information. Furthermore, a lot of these details
don't matter regarding the cache, so cache reuse might be suboptimal.
A more general problem is that OPcache calculates the system hash during
its startup, while other extensions may not even have been loaded. Not
sure if that can be resolved.
--
Christoph M. Becker