Turns out I need to use tvSet with temporaries. Also removes
unused tvSetObject*, and replaces some tvSetNull* callsites with using
make_tv temporaries.
I noticed that directorty structure of hphp/system was a bit scattered, so
I consolidated things to reduce the total number of folders and to put
related things together with each other.
This diff moves the contents of "hphp/system/classes_hhvm" into
"hphp/system", it moves the contents of "hphp/system/lib" into
"hphp/system", moves "hphp/idl" to "hphp/system/idl", and moves the
contents of "hphp/system/globals" into "hphp/system/idl".
I was learning from @jdelong and he said that you should use
double quotes for local includes and angle brackets for library
includes. I asked why our code was the way it was, and he said he wanted
to clean it up. I beat him to it :)
Conflicts:
hphp/runtime/base/server/admin_request_handler.cpp
hphp/runtime/vm/named_entity.h
In order to build a dependency graph of continuation execution and data-fetching in PHP-land, we need a few instrumentation points in the asio_ext HHVM extension. There are 4 additions required:
1. Callback when a continuation finishes successfully.
2. Callback when a continuation blocks on a wait_handle.
3. Get array of WaitHandles a GenArrayWaitHandle is waiting on.
4. Get WaitHandle that the SetResultToRefWaitHandle is waiting on.
I don't think this should really affect performance, as in the normal case, nothing has changed, but you never know... I'm also not sure who should be reviewing this, so I've just added @jan for now. If you could pile other people on, that would be cool.
sandcastle appears to be broken.
For cppext static methods we have a "ti_" method that takes an extra unused
parameter "const char* cls" and then a "t_" wrapper method that calls the
"ti_" method.
This makes things unnecessarily complicated when writing HipHop extensions.
Let's get rid of the extra unused parameter "cls" and the unnecessary "t_"
wrapper method.
Provide a Static{Result,Exception}WaitHandle::Create() static method for
internal use, use it by GenArrayWaitHandle.
Avoids one inc/decref (Array -> Variant -> m_resultOrException) if
GenArray received an array of finished dependencies.
If a GenArrayWaitHandle is imported, the current implementation imports
only the active child. Try to import other children as well to increase
parallelism.
enterContext() can throw an exception if a cross-context dependency
cycle is found. It is safe to ignore such exception when importing
non-active children. The import will be attempted and fail again once
onBlocked() reaches the dependency that causes the cycle.
Verify sanity of input array of dependencies in advance. Callers get the
error earlier and it also makes it easier to work with the array outside
of the main loop.
We only used it to get the values of certain class constants,
and to define the ObjectStaticCallbacks for every class.
We can put the class constants directly into the class_map
(we should have done that before for perf reasons), and then
the only remaining use of ObjectStaticCallbacks is to proxy
the Class* for each builtin class. So just use the Class*
directly.
Once this is in, Im just a small step away from eliminating
make -C hphp/system - so Im leaving a lot of dead code here.
Its going to be easier to delete it en masse, rather than
try to pick and chose now.
enterContext() throws an exception when cross-context cycle is found.
The problem is that it modifies state before the exception is thrown,
assuming that the call will succeed.
When an exception is thrown, a dependency is left in invalid state, with
parent being in more specific context. This breaks exitContext()
algorithm and results in either internal invariant violations as seen
in #2091939, or memory corruptions and crashes as seen in #2125762.
Let's fix it by modifying state after returning back from recursive call
instead of before doing such call. This was previously unsafe in case we
tried to import dependency loop. Once D720506 is committed, dependency
loops will not exist anymore.
Currently, we detect dependency loops by waiting until there is nothing
else to execute. If the wait handle we are waiting for did not finish,
it means it is in a cycle. We find the cycle by simply following the
dependency chain. Once the cycle is found, one edge is eliminated and an
exception is injected.
There are multiple problems with this approach:
1. Unability to exit contet safely
We are unable to exit context safely. When a context is exited, all wait
handles in that context must be kicked out. But we maintain only
references to the SCHEDULED wait handles + BLOCKED wait handles that
recursively depend on them.
If we do not kick out all unfinished wait handles, we end up in
corrupted state.
2. Unability to break edge that caused the cycle
Once the cycle is detected, we don't know which edge caused the cycle to
be formed. We can only use heuristics to eliminate the edge that likely
formed the cycle, we cannot be sure. This may make it very hard to fix
the PHP code that caused the cycle.
Solution:
This diff implements online cycle detection with a naive approach of
visiting the dependency chain from child at a time new edge between
parent and child is being added. If a parent is visited, a cycle is
found. Otherwise we eventually reach non-BLOCKED wait handle as it is
guaranteed the rest of the graph is cycle-free.
Currently, wait handles store pointer to the context they are in. This
pointer is not protected with reference counting, as it is expected that
whenever a context is exited, references to it are cleaned thru
exitContext() mechanism.
If a bug is present that violates this assumption, it is impossible to
guard against invalid pointer access and a hard to debug memory
corruption occurs.
Since the structure of contexts is a simple stack, let's reference them
by index instead of by pointer.
As a bonus, one pointer worth of memory is saved for every non-trivial wait handle.
The actual bugs will be fixed by the next 2 diffs that do:
1. implement online cycle detection
2. do enterContext() atomically and properly handle failure
Avoid dynamic_cast<> on fast paths, use o_instanceof(StaticString)
instead. Saves about ~0.2-0.3% of CPU time.
Once HPHPc is gone, we will convert these calls to HHVM-specific API.
Thanks @bmaurer for discovery and @mwilliams for suggestion how to fix
it.
This change is mostly for FB internal organizational reasons.
Building is not effected beyond the fact that the target now
lands in hphp/hhvm/hhvm rather than src/hhvm/hhvm.
Jordan DeLong