Add dumpsys integration for the native input dispatcher.
Add some InputDevice API stubs.
Add an appendFormat helper method to String8 for printf style
string formatting mainly for debugging purposes.
Use generic ArrayList<WindowState> everywhere in WindowManagerService
to eliminate unnecessary casts all over.
Change-Id: I9d1e3bd90eb7222d10620200477f11b7bfd25e44
This significantly re-works the native key dispatching code to
allow events to be pre-dispatched to the current IME before
being processed by native code. It introduces one new public
API, which must be called after retrieving an event if the app
wishes for it to be pre-dispatched.
Currently the native code will only do pre-dispatching of
system keys, to avoid significant overhead for gaming input.
This should be improved to be smarted, filtering for only
keys that the IME is interested in. Unfortunately IMEs don't
currently provide this information. :p
Change-Id: Ic1c7aeec8b348164957f2cd88119eb5bd85c2a9f
Added several new coordinate values to MotionEvents to capture
touch major/minor area, tool major/minor area and orientation.
Renamed NDK input constants per convention.
Added InputDevice class in Java which will eventually provide
useful information about available input devices.
Added APIs for manufacturing new MotionEvent objects with multiple
pointers and all necessary coordinate data.
Fixed a bug in the input dispatcher where it could get stuck with
a pointer down forever.
Fixed a bug in the WindowManager where the input window list could
end up containing stale removed windows.
Fixed a bug in the WindowManager where the input channel was being
removed only after the final animation transition had taken place
which caused spurious WINDOW DIED log messages to be printed.
Change-Id: Ie55084da319b20aad29b28a0499b8dd98bb5da68
in this commit:
- implemented the C stub
- implemented the binder interfaces involved
- implemented most of the C++ client side
missing:
- SensorManager cannot connect to the SensorServer yet
(because there is no SensorServer yet)
Change-Id: I75010cbeef31c98d6fa62fd5d388dcef87c2636b
And also:
- APIs to show and hide the IME, and control its interaction with the app.
- APIs to tell the app when its window resizes and needs to be redrawn.
- API to tell the app the content rectangle of its window (to layout
around the IME or status bar).
There is still a problem with IME interaction -- we need a way for the
app to deliver events to the IME before it handles them, so that for
example the back key will close the IME instead of finishing the app.
Change-Id: I37b75fc2ec533750ef36ca3aedd2f0cc0b5813cd
Add native Parcel methods analogous to the Java versions.
Currently, these don't do much, but upcoming StrictMode work changes
the RPC calling conventions in some cases, so it's important that
everybody uses these consistently, rather than having a lot of code
trying to parse RPC responses out of Parcels themselves.
As a summary, the current convention that Java Binder services use is
to prepend the reply Parcel with an int32 signaling the exception
status:
0: no exception
-1: Security exception
-2: Bad Parcelable
-3: ...
-4: ...
-5: ...
... followed by Parceled String if the exception code is non-zero.
With an upcoming change, it'll be the case that a response Parcel can,
non-exceptionally return rich data in the header, and also return data
to the caller. The important thing to note in this new case is that
the first int32 in the reply parcel *will not be zero*, so anybody
manually checking for it with reply.readInt32() will get false
negative failures.
Short summary: If you're calling into a Java service and manually
checking the exception status with reply.readInt32(), change it to
reply.readExceptionCode().
Change-Id: I23f9a0e53a8cfbbd9759242cfde16723641afe04
Also other cleanup and fixes:
- We now properly set the default window format to 565.
- New APIs to set the window format and flags from native code.
- Tweaked glue for simpler handling of the "destroy" message.
- Um, other stuff.
Change-Id: Id7790a21a2fa9a19b91854d225324a7c1e7c6ade
This factors out the boiler-plate code from the sample
app to a common glue code that can be used for everyone
writing this style of app: a dedicated app thread that
takes care of waiting for events and processing them.
As part of doing this, ALooper has a new facility to allow
registration of fds that cause ALooper_pollOnce() to return
the fd that has data, allowing the app to drive the loop
without callbacks. Hopefully this makes some people feel better. :)
Also do some other cleanup of the ALooper API, plus some
actual documentation.
Change-Id: Ic53bd56bdf627e3ba28a3c093faa06a92be522b8
Removed old input dispatch code.
Refactored the policy callbacks.
Pushed a tiny bit of the power manager state down to native.
Fixed long press on MENU.
Made the virtual key detection and cancelation a bit more precise.
Change-Id: I5d8c1062f7ea0ab3b54c6fadb058c4d5f5a9e02e
This allows us to avoid exposing the file descriptor of
the event queue; instead, you attach an event queue to
a looper. This will also should allow native apps to be
written without the need for a separate thread, by attaching
the event queue to the main thread's looper and scheduling
their own messages there.
Change-Id: I38489282635895ae2cbfacb88599c1b1cad9b239
Not yet hooked up to anything in the NDK, but requires renaming
the existing android_native_window_t type everywhere.
Change-Id: Iffee6ea39c93b8b34e20fb69e4d2c7c837e5ea2e
This change mainly unwinds a premature optimization in the
dispatch pipeline.
To test HOME injection, run 'adb shell input keyevent 3'.
Change-Id: I1c4b7377c205da7c898014b8b07fc6dc1d46e4dd
The native code now maintains a list of all keys that may use
default handling. If the app finishes one of these keys
without handling it, the key will be passed back off to Java
for default treatment.
Change-Id: I6a842a0d728eeafa4de7142fae573f8c11099e18
Set a default orientation of ROTATION_0.
Added some more careful checks based on whether we have valid
absolute axis information from the driver.
Reset key repeating during configuration changes since the keyboard
device may have been removed.
Change-Id: I685960828acffcb17595fc5683309e8064a76714
Target identification is now fully native.
Fixed a couple of minor issues related to input injection.
Native input enabled by default, can be disabled by setting
WindowManagerPolicy.ENABLE_NATIVE_INPUT_DISPATCH to false.
Change-Id: I7edf66ed3e987cc9306ad4743ac57a116af452ff
Sometimes the wrong fd was accessed when the device was addressed
by device id.
The earlier implementation assumed that two arrays were in sync
but one of them was compacted when devices were removed. Instead
of that dependency the device now keeps track of it's file descriptor.
Change-Id: I2b8a793d76b89ab464ae830482b309fe86031671
when assigning a smart pointer to another one, we need to make
sure to read all the data we need from the right-hand-side
reference (the assignee) before we decRef the assigned.
This bug would cause linked-list of smart-pointers to fail
miserably.
Change-Id: Ibb554c15fddf909f7737c632b7c80322e80ea93f
Provides the basic infrastructure for a
NativeActivity's native code to get an object representing
its event stream that can be used to read input events.
Still work to do, probably some API changes, and reasonable
default key handling (so that for example back will still
work).
Change-Id: I6db891bc35dc9683181d7708eaed552b955a077e
Added ANRs handling.
Added event injection.
Fixed a NPE ActivityManagerServer writing ANRs to the drop box.
Fixed HOME key interception.
Fixed trackball reporting.
Fixed pointer rotation in landscape mode.
Change-Id: I50340f559f22899ab924e220a78119ffc79469b7
This is (intendend to be) a no-op change.
At this stage, Binder RPCs just have an additional uint32 passed around
in the header, right before the interface name. But nothing is actually
done with them yet. That value should right now always be 0.
This now boots and seems to work.
Change-Id: I135b7c84f07575e6b9717fef2424d301a450df7b
Added more tests.
Fixed a regression in Vector.
Fixed bugs in pointer tracking.
Fixed a starvation issue in PollLoop when setting or removing callbacks.
Fixed a couple of policy nits.
Modified the internal representation of MotionEvent to be more
efficient and more consistent.
Added code to skip/cancel virtual key processing when there are multiple
pointers down. This helps to better disambiguate virtual key presses
from stray touches (such as cheek presses).
Change-Id: I2a7d2cce0195afb9125b23378baa94fd2fc6671c
Refactored the code to eliminate potential deadlocks due to re-entrant
calls from the policy into the dispatcher. Also added some plumbing
that will be used to notify the framework about ANRs.
Change-Id: Iba7a10de0cb3c56cd7520d6ce716db52fdcc94ff
The old dispatch mechanism has been left in place and continues to
be used by default for now. To enable native input dispatch,
edit the ENABLE_NATIVE_DISPATCH constant in WindowManagerPolicy.
Includes part of the new input event NDK API. Some details TBD.
To wire up input dispatch, as the ViewRoot adds a window to the
window session it receives an InputChannel object as an output
argument. The InputChannel encapsulates the file descriptors for a
shared memory region and two pipe end-points. The ViewRoot then
provides the InputChannel to the InputQueue. Behind the
scenes, InputQueue simply attaches handlers to the native PollLoop object
that underlies the MessageQueue. This way MessageQueue doesn't need
to know anything about input dispatch per-se, it just exposes (in native
code) a PollLoop that other components can use to monitor file descriptor
state changes.
There can be zero or more targets for any given input event. Each
input target is specified by its input channel and some parameters
including flags, an X/Y coordinate offset, and the dispatch timeout.
An input target can request either synchronous dispatch (for foreground apps)
or asynchronous dispatch (fire-and-forget for wallpapers and "outside"
targets). Currently, finding the appropriate input targets for an event
requires a call back into the WindowManagerServer from native code.
In the future this will be refactored to avoid most of these callbacks
except as required to handle pending focus transitions.
End-to-end event dispatch mostly works!
To do: event injection, rate limiting, ANRs, testing, optimization, etc.
Change-Id: I8c36b2b9e0a2d27392040ecda0f51b636456de25
Surfaces can now be parcelized and sent to remote
processes. When a surface crosses a process
boundary, it looses its connection with the
current process and gets attached to the new one.
Change-Id: I39c7b055bcd3ea1162ef2718d3d4b866bf7c81c0
this is called for each relayout() and used to create a full Surface (cpp)
which in turn did some heavy work (including an IPC with surfaceflinger),
most of the time to destroy it immediatelly when the returned surface
(the one in the parcel) was the same.
we now more intelligentely read from the parcel and construct the new
object only if needed.
Change-Id: Idfd40d9ac96ffc6d4ae5fd99bcc0773e131e2267
SurfaceComposerClient now only exist on the WindowManager side,
the client side uses the new SurfaceClient class, which only
exposes what a client needs.
also instead of keeping mappings from IBinder to SurfaceComposerClients
we have a SurfaceClient per Surface (referring to the same IBinder), this
is made possible by the fact that SurfaceClient is very light.
Change-Id: I6a1f7015424f07871632a25ed6a502c55abfcfa6
the new native_window_set_buffers_geometry allows
to specify a size and format for all buffers to be
dequeued. the buffer will be scalled to the window's
size.
Change-Id: I2c378b85c88d29cdd827a5f319d5c704d79ba381
this method can be used to change the number of buffers
associated to a native window. the default is two.
Change-Id: I608b959e6b29d77f95edb23c31dc9b099a758f2f
this change introduces R/W locks in the right places.
on the server-side, it guarantees that setBufferCount()
is synchronized with "retire" and "resize".
on the client-side, it guarantees that setBufferCount()
is synchronized with "dequeue", "lockbuffer" and "queue"
Change the way zip archives are handled. This is necessary to deal with
very large (~1GB) APK files, for which our current approach of mapping
the entire file falls over.
We now do the classic scavenger hunt for the End Of Central Directory
magic on a buffer of data read from the file, instead of a memory-mapped
section. We use what we find to create a map that covers the Central
Directory only.
If the caller is interested in unpacking the file contents, we have to
do an additional file read to discover the size of the Local File Header
section so we can skip past it.
This is based on Change I745fb15abb in the dalvik tree. Both
implementations share a common ancestry, but the cost of unifying them
outweighs the benefits of wrapping C calls.
Change-Id: Iddacb50fe913917c2845708a530872d65fdbe620
This change adds the methods necessary to use sp<> to handle refcounting
android_native_window_t and android_native_buffer_t. The new methods forward
the refcounting operations to the corresponding android_native_base_t
functions.
Change-Id: I7de8e262728e439bc1efdf69374a2a9f6f432ced
Merge commit 'ca48c88c3d5733c4405a2fc4f7d9bb7fbba3d43f' into kraken
* commit 'ca48c88c3d5733c4405a2fc4f7d9bb7fbba3d43f':
Make static versions of libutils and libbinder.
Merge commit '8a8658a5de261c2da72d431940877bd054bc9837' into froyo-plus-aosp
* commit '8a8658a5de261c2da72d431940877bd054bc9837':
Make static versions of libutils and libbinder.
Fix some small static-initialization-order issues (and a static-
initializers-missing issue) that result from doing so. The static
libraries don't actually get used for anything real at the moment --
they're used for perf tests of bug 2660235.
Bug: 2660235
Change-Id: Iee2f38f79cc93b395e8d0a5a144ed92461f5ada0
Merge commit 'f78964490d8098387d51444c87bf520ad3f674e2' into kraken
* commit 'f78964490d8098387d51444c87bf520ad3f674e2':
Add new keycodes for the convenience of Japanese IMEs
Call register_localized_collators() with the current locale.
Fixed deserialization problem in DatePicker.
Fix for bug 2467152 files with spaces fail to open.
Set alpha value for newly created dim surface.
telephony: Fix CID when CID is unknown
Not complete, only for experimentation at this point.
This includes a reworking of how screen size configurations are matched,
so that if you are on a larger screen we can select configurations for
smaller screens if there aren't any exactly matching the current screen.
The screen size at which we switch to xlarge has been arbitrarily
chosen; the compatibility behavior has not yet been defined.
Change-Id: I1a33b3818eeb51a68fb72397568c39ab040a07f5
the reason for the above change is that waitForCondition() had become
large over time, mainly to handle error cases, using inlines to
evaluate the condition doesn't buys us much anymore while it increases
code size.
Change-Id: I2595d850832628954b900ab8bb1796c863447bc7
in the undoDequeue() case, 'tail' was recalculated from 'available' and 'head'
however there was a race between this and retireAndLock(), which could cause
'tail' to be recalculated wrongly.
the interesting thing though is that retireAndLock() shouldn't have any impact
on the value of 'tail', which is client-side only attribute.
we fix the race by saving the value of 'tail' before dequeue() and restore it
in the case of undoDequeue(), since we know it doesn't depend on retireAndLock().
Change-Id: I4bcc4d16b6bc4dd93717ee739c603040b18295a0
Merge commit 'f021d12f6f7116e9275cd3553a349ce5cb8aab14' into kraken
* commit 'f021d12f6f7116e9275cd3553a349ce5cb8aab14':
Allow META* macros outside of the framework
Fix printing order of phone objects creation
The META* macros are useful outside of the framework
for other systems implementing Binder interfaces, but
they depend upon the android namespace. This includes
the appropriate namespace operations, which should be
sane even in that android namespace.
Change-Id: If600156c65191f51f487d0ee301d9f9f532b263d
also increase the dirtyregion size from 1 to 6 rectangles.
Overall we now need 27KiB process instead of 4KiB
Change-Id: Iebda5565015158f49d9ca8dbcf55e6ad04855be3
Merge commit '26f6163557980062dbb203388b3d0794ee0d06f7' into kraken
* commit '26f6163557980062dbb203388b3d0794ee0d06f7':
fix [2599939] "cannot play video" after open/close a video player a dozen of times
Merge commit '0a4ab1b9b4c7b891c1ecb67eed99e9c9b30c93aa' into froyo-plus-aosp
* commit '0a4ab1b9b4c7b891c1ecb67eed99e9c9b30c93aa':
fix [2599939] "cannot play video" after open/close a video player a dozen of times
get rid off the MAP_ONCE flag is MemoryHeapBase (as well as it's functionality),
this feature should not be used anymore.
the software renderer was incorrectly using the default ctor which set MAP_ONCE,
causing the leak. the software renderer itself is incorrectly used while coming
back from sleep.
Change-Id: I123621f8d140550b864f352bbcd8a5729db12b57
this is used in a few places to get access to the android.view.Surface
native surface. use a macro instead. Also rename the field to mNativeSurface.
Change-Id: I1c6dea14abd6b8b1392c7f97b304115999355094
Condition must be initialized with SHARED for the old behavior, where
they can be used accross processes.
Updated the two places android that require SHARED conditions.
PRIVATE conditions (and mutexes) use more efficient syscalls.
Change-Id: I9a281a4b88206e92ac559c66554e886b9c62db3a
the framebuffer implementation doesn't do anything special with this
but the surfaceflinger implementation makes sure the surface is not used
by two APIs simultaneously.
Change-Id: Id4ca8ef7093d68846abc2ac814327cc40a64b66b
This loosens our restriction on many manifest attributes requiring
literal string values, to allow various ones to use values from
resources. This is only allowed if the resource value does not change
from configuration changes, and the restriction is still in place
for attributes that are core to security (requesting permissions) or
market operation (used libraries and features etc).
Change-Id: I4da02f6a5196cb6a7dbcff9ac25403904c42c2c8
Extract all UI behavior from dock observer and ACTION_DOCK_EVENT.
Also introduce a desk type to go along with the car type all through
the resource system, since we now need to have corresponding high-level
broadcasts for desk dock mode. As part of that I also reworked some
of the logic for switching modes to all funnel through a single
update() call that looks all of the current state to decide what to
do next, and fixed various locking issues.
In addition I found there were bugs in the configuration change
handling causing us to only switch into the car mode config and
then never get out of it. Unfortunately now that we are actually
changing the configuration for each mode change, the transitions
between them are really crummy as we restart all kinds of
activities. :(
And related:
- The aapt tool now sets a resource configurations sdk level to match any configs
that have been set (for example if you specify density your sdk level will be
at least 4).
- New option to modify the targetPackage attribute of instrumentation.
- Clean up of aapt options help.
- Fix of UI type values to leave 0 for "unspecified".
- Make the UI mode config APIs public.
StringBlock instances containing UTF-8 strings use a cache to convert
into UTF-16, but using that cache and then using a JNI call to NewString
causes the UTF-8 string as well as two copies of the UTF-16 string to
be held in memory. Getting the UTF-8 string directly from the StringPool
eliminates one copy of the UTF-16 string being held in memory.
This is part 1. Part 2 will include ResXMLParser optimizations.
Change-Id: Ibd4509a485db746d59cd4b9501f544877139276c
Add a Flattenable interface to libutils which can be used to flatten
an object into bytestream + filedescriptor stream.
Parcel is modified to handle Flattenable. And GraphicBuffer implements
Flattenable.
Except for the overlay classes libui is now independent of libbinder.
Unicode.cpp used a packed data table for character data that essentially
duplicated ICU's functionality.
Change-Id: Ia68fe4ac94e89dc68d9a3f45f33f6e648a5500b7
Remove some utility functions for discovering character data
that ICU probably took over a while ago.
Change-Id: I97abe4de2f51eb2bf48679941258bc501184c3dc
The device mode is now called ui mode. Furthermore is the order of
precedence for the resources now in such a way that the ui mode needs
to be specified after the orientation and before the density.
The ui mode can be set, like it is done for the locale, as follows:
IActivityManager am = ActivityManagerNative.getDefault();
Configuration config = am.getConfiguration();
config.uiMode = Configuration.UI_MODE_TYPE_CAR | Configuration.UI_MODE_NIGHT_ANY;
am.updateConfiguration(config);
To allow users to disable the car mode and set the night mode the IUiModeManager
interface is used.
The automatic night mode switching will be added in a separate change.
A typo caused GL_AMBIENT_AND_DIFFUSE to only set the the ambient color.
Fix another typo which caused the viewer position to be wrong for
specular highlights.
Switch back to eye-space lighting, since there are still some issues
with some demos (San Angeles in particular).
At some point the implementation became complicated because of
SurfaceFlinger's special needs, since we are now relying on gralloc
we can go back to much simpler MemoryDealer.
Removed HeapInterface and AllocatorInterface, since those don't need
to be paramterized anymore. Merged SimpleMemory and Allocation.
Made SimplisticAllocator non virtual.
Removed MemoryDealer flags (READ_ONLY, PAGE_ALIGNED)
Removed a lot of unneeded code.
Allows "aapt dump --values resource" to print out whether a string in a
ResStringPool is in UTF-8 or UTF-16 encoding.
Change-Id: I6478884a70a3b46fee862dece6cb33454fc34843
This is a very simply implementation: upon receiving an IPC, if the handling
thread is at a background priority (the driver will have taken care of
propagating this from the calling thread), then stick it in to the background
scheduling group. Plus an API to turn this off for the process, which is
used by the system process.
This also pulls some of the code for managing scheduling classes out of
the Process JNI wrappers and in to some convenience methods in thread.h.
Allows the use of UTF-8 for packing resources instead of the
default of UTF-16 for Java. When strings are extracted from the
ResStringPool, they are converted to UTF-16 and the result is
cached for subsequent calls.
When using aapt to package, add in the "-8" switch to pack the
resources using UTF-8. This will result in the value, key, and
type strings as well as the compiled XML string values taking
significantly less space in the final application package in
most scenarios.
Change-Id: I129483f8b3d3b1c5869dced05cb525e494a6c83a
Surface::validate() could sometimes dereference a null pointer before checking it wasn't null.
This will prevent the application to crash when given bad parameters or used incorrectly.
However, the bug above probably has another cause.
we lost the concept of vertical stride when moving video playback to EGLImage.
Here we bring it back in a somewhat hacky-way that will work only for the
softgl/mdp backend.
Use EGLImageKHR instead of copybit directly.
We now have the basis to use streaming YUV textures (well, in fact
we already are). When/if we use the GPU instead of the MDP we'll
need to make sure it supports the appropriate YUV format.
Also make sure we compile if EGL_ANDROID_image_native_buffer is not supported
This also fixes [2152536] ANR in browser
When SF is enqueuing buffers faster than SF dequeues them.
The update flag in SF is not counted and under some situations SF will only
dequeue the first buffer. The state at this point is not technically
corrupted, it's valid, but just delayed by one buffer.
In the case of the Browser ANR, because the last enqueued buffer was delayed
the resizing of the current buffer couldn't happen.
The system would always fall back onto its feet if anything -else- in
tried to draw, because the "late" buffer would be picked up then.
A window is created and the browser is about to render into it the
very first time, at that point it does an IPC to SF to request a new
buffer. Meanwhile, the window manager removes that window from the
list and the shared memory block it uses is marked as invalid.
However, at that point, another window is created and is given the
same index (that just go freed), but a different identity and resets
the "invalid" bit in the shared block. When we go back to the buffer
allocation code, we're stuck because the surface we're allocating for
is gone and we don't detect it's invalid because the invalid bit has
been reset.
It is not sufficient to check for the invalid bit, I should
also check that identities match.
When EGLImage extension is not available, SurfaceFlinger will fallback to using
glTexImage2D and glTexSubImage2D instead, which requires 50% more memory and an
extra copy. However this code path has never been exercised and had some bugs
which this patch fix.
Mainly the scale factor wasn't computed right when falling back on glDrawElements.
We also fallback to this mode of operation if a buffer doesn't have the adequate
usage bits for EGLImage usage.
This changes only code that is currently not executed. Some refactoring was needed to
keep the change clean. This doesn't change anything functionaly.
The ANR is caused by SurfaceFlinger waiting for buffers of a removed surface to become availlable.
When it is removed from the current list, a Surface is marked as NO_INIT, which causes SF to return
immediately in the above case. For some reason, the surface here wasn't marked as NO_INIT.
This change makes the code more robust by always (irregadless or errors) setting the NO_INIT status
in all code paths where a surface is removed from the list.
Additionaly added more information in the logs, should this happen again.
a new method, compostionComplete() is added to the framebuffer hal, it is used by surfaceflinger to signal the driver that the composition is complete, BEFORE it releases its client. This gives a chance to the driver to
This implements support for devices whose hardware can hide
their navigation keys. It works much like the existing keyboardHidden
configuration, and for compatibility uses the same configuration
change bit.
Also add FLAG_TURN_ON_SCREEN for windows, which has the system
cause the screen to be turned on when the window is displayed.
Great fun when used with FLAG_SHOW_WHEN_LOCKED!
Change-Id: I0b867f19af85cfd8786a14cea194b34f7bdd9b7a
Take 2. We needed to check that the usage flags are "good enough" as opposed to "the same".
This reverts commit 8f17a762fe9e9f31e4e86cb60ff2bfb6b10fdee6.
we could have several thread waiting on the condition and they all need to wake-up.
also added a debug "mTid" field in the class, which contains the tid of the thread (as opposed to pthread_t), this
is useful when debugging under gdb for instance.
Rewrote SurfaceFlinger's buffer management from the ground-up.
The design now support an arbitrary number of buffers per surface, however the current implementation is limited to four. Currently only 2 buffers are used in practice.
The main new feature is to be able to dequeue all buffers at once (very important when there are only two).
A client can dequeue all buffers until there are none available, it can lock all buffers except the last one that is used for composition. The client will block then, until a new buffer is enqueued.
The current implementation requires that buffers are locked in the same order they are dequeued and enqueued in the same order they are locked. Only one buffer can be locked at a time.
eg. Allowed sequence: DQ, DQ, LOCK, Q, LOCK, Q
eg. Forbidden sequence: DQ, DQ, LOCK, LOCK, Q, Q
