Difference between revisions of "Effort/Make VCL Thread-Transparent"
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VCL hampers thread transparency in the following ways: | VCL hampers thread transparency in the following ways: | ||
− | * It is | + | * It is [[Uno/Spec/Thread Affine | Thread Affine]] under Windows - bascially letting shine through the Win32 thread affinity regarding window messages, window construction and window destruction. |
− | * It provides the | + | * It provides the Solar MutEx, which needs to be acquired befor VCL can be called. |
− | * It completely releases the | + | * It completely releases the Solar MutEx in some sitations, without any hints at the API. |
− | VCLs internals are not protected against concurrent access, except by the | + | VCLs internals are not protected against concurrent access, except by the Solar MutEx, which needs to be locked from the outside. VCLs API only provides blocking or polling functions for accessing the event loop, which is especially bad as it does not offer a way, to avoid long acquired MutExes, while waiting for events, except by actively polling. |
To make VCL thread transparent, we propose, to | To make VCL thread transparent, we propose, to | ||
− | * remove the | + | * remove the Solar MutEx completely and declare VCL to be non-thread-safe, and to |
− | * encapsulate calls to the | + | * encapsulate calls to the [[Uno/Spec/Thread Affine | Thread Affine]] Win32 API, in a way, that this thread affinity is not visible from the outside. |
The goal being that VCL behaves as an ordinary library, not showing any threading behavior at all. | The goal being that VCL behaves as an ordinary library, not showing any threading behavior at all. | ||
− | To ensure short | + | To ensure short MutEx acquiration times, we propose to |
− | * add a system handle providing API, so that we can poll/select the handle and only need to enter VCL in case of an event. | + | * add a system handle providing API, so that we can poll/select on the handle in an outer event loop, and only need to enter VCL in case of an event. |
Side effects: | Side effects: | ||
* Some Win32 based OOo components (DDE) expect their initialising thread eventually to enter the VCL event loop, to dispatch messages for objects created during this initialization. These implementations need to be adapted, to either delegate Win32 thread affine calls into VCLs new internal thread, or to create a thread for dispatching purposes by their own. | * Some Win32 based OOo components (DDE) expect their initialising thread eventually to enter the VCL event loop, to dispatch messages for objects created during this initialization. These implementations need to be adapted, to either delegate Win32 thread affine calls into VCLs new internal thread, or to create a thread for dispatching purposes by their own. | ||
− | * With the removal of the | + | * With the removal of the Solar MutEx, VCL can not release a protecting MutEx anymore, which it currently does when executing a dialog. That means, that a protecting MutEx will stay acuired, basically disallowing other threads to enter VCL. This is needs to be addressed by [[Async Dialogs | making the office dialogs asynchron]]. |
Revision as of 14:05, 21 April 2006
Status: in progress
VCL provides the OOo base widget set and windowing abstraction. It manages the event loop and dispatches the events. It also owns the display connection and manages various resources, e.g. fonts.
VCL hampers thread transparency in the following ways:
- It is Thread Affine under Windows - bascially letting shine through the Win32 thread affinity regarding window messages, window construction and window destruction.
- It provides the Solar MutEx, which needs to be acquired befor VCL can be called.
- It completely releases the Solar MutEx in some sitations, without any hints at the API.
VCLs internals are not protected against concurrent access, except by the Solar MutEx, which needs to be locked from the outside. VCLs API only provides blocking or polling functions for accessing the event loop, which is especially bad as it does not offer a way, to avoid long acquired MutExes, while waiting for events, except by actively polling.
To make VCL thread transparent, we propose, to
- remove the Solar MutEx completely and declare VCL to be non-thread-safe, and to
- encapsulate calls to the Thread Affine Win32 API, in a way, that this thread affinity is not visible from the outside.
The goal being that VCL behaves as an ordinary library, not showing any threading behavior at all.
To ensure short MutEx acquiration times, we propose to
- add a system handle providing API, so that we can poll/select on the handle in an outer event loop, and only need to enter VCL in case of an event.
Side effects:
- Some Win32 based OOo components (DDE) expect their initialising thread eventually to enter the VCL event loop, to dispatch messages for objects created during this initialization. These implementations need to be adapted, to either delegate Win32 thread affine calls into VCLs new internal thread, or to create a thread for dispatching purposes by their own.
- With the removal of the Solar MutEx, VCL can not release a protecting MutEx anymore, which it currently does when executing a dialog. That means, that a protecting MutEx will stay acuired, basically disallowing other threads to enter VCL. This is needs to be addressed by making the office dialogs asynchron.
Title | Spec | % | Changed | Impl | % | Changed | Test | % | Changed |
API providing a system handle to pollable for messages | 0.0 | 0% | 12/14/2005 | proof | 0% | 12/14/2005 | |||
Remove the SolarMutex | 0.0 | 0% | 12/14/2005 | proof | 0% | 12/14/2005 | |||
Encapsulate Win32 thread affinity | 0.0 | 0% | 12/14/2005 | proof | 0% | 12/14/2005 | |||
Adapt DDE to use same thread for initialisation as VCL is going to use for internal purposes | 0.0 | 0% | 04/05/2006 | open | 0% | 04/05/2006 | 0% | 04/05/2006 | |
Rework OOo code, where dialogs get executed and concurrent threads need to enter VCL | 0.0 | 0% | 04/05/2006 | proof | 0% | 04/05/2006 | 0% | 04/05/2006 |
The above tasks are going to depend on the Extended UNO Threading Framework, therefor VCL Thread Transparency will earliest be available after the UTF.