The audio enqueuer thread goes to sleep when there is no more audio data
present, and through normal Core::EventLoop events it can be woken up.
However, that waking up only happens when the thread is not currently
running, so that the wake-up events don't queue up and cause weirdness.
The atomic variable responsible for keeping track of whether the thread
is active can lead to a racy deadlock however, where the audio enqueuer
thread will never wake up again despite there being audio data to
enqueue. Consider this scenario:
- Main thread calls into async_enqueue. It detects that according to the
atomic variable, the other thread is still running, skipping the event
queue wake.
- Enqueuer thread has just finished playing the last chunk of audio and
detects that there is no audio left. It enters the if block with the
dbgln "Reached end of provided audio data..."
- Main thread enqueues audio, making the user sample queue non-empty.
- Enqueuer thread does not check this condition again, instead setting
the atomic variable to indicate that it is not running. It exits into
an event loop sleep.
- Main thread exits async_enqueue. The calling audio enqueuing system
(see e.g. Piano, but all of them function similarly) will wait until
the enqueuer thread has played enough samples before async_enqueue is
called again. However, since the enqueuer thread will never play any
audio, this condition is never fulfilled and audio playback deadlocks
This commit fixes that by allowing the event loop to not enqueue an
event that already exists, therefore overloading the audio enqueuer
event loop by at maximum one message in weird situations. We entirely
get rid of the atomic variable and the race condition is prevented.
This will conflict with apps that don't use this thread and it also
creates unnecessary overhead for non-enqueuing clients like AudioApplet.
Use the new Thread is_started info to start the thread only if necessary
(on first call to async_enqueue).
Users can now determine whether a thread has been started or not. A
started thread might also have already terminated.
Implementation note: We *could* detect this with pthread APIs maybe, but
this is much simpler.
We likely won't be able to test `pthread_cancel` itself, but this at
least makes sure that we use the correct values by default and that we
correctly reject invalid values.
In the generated unique string list, index 0 is the empty string, and is
used to indicate a value doesn't exist in the CLDR. Check for this
before returning an empty calendar symbol.
For example, an upcoming commit will add the fixed day period "noon",
which not all locales support.
Commit ec7d535 only partially handled the case of flexible day periods
rolling over midnight, in that it only worked for hours after midnight.
For example, the en locale defines a day period range of [21:00, 06:00).
The previous method of adding 24 hours to the given hour would change
e.g. 23:00 to 47:00, which isn't valid.
Previously, end block was inconsistent. GUIDPartitionTable treated
end block as an inclusive bound, while MBRPartitionTable and
EBRPartitionTable treated end block as an exclusive bound.
Now all three treat end block as an inclusive upper bound.
This adds a new application PartitionEditor which will eventually be
used to create and edit partition tables. Since LibPartition does not
know how to write partition tables yet, it is currently read-only.
Devices are discovered by scanning /dev for block device files.
Since block devices are chmod 600, PartitionEditor be must run as root.
By default Serenity uses the entire disk for the ext2 filesystem
without a partition table. This isn't useful for testing as the
partition list for the default disk will be empty. To test properly,
I created a few disk images using various partitioning schemes
(MBR, EBR, and GPT) and attached them using the following command:
export SERENITY_EXTRA_QEMU_ARGS="
-drive file=/path/to/mbr.img,format=raw,index=1,media=disk
-drive file=/path/to/ebr.img,format=raw,index=2,media=disk
-drive file=/path/to/gpt.img,format=raw,index=3,media=disk"
The existing File::is_device() helpers don't distinguish between
block and char devices. This commit adds File::is_block_device() and
File::is_char_device() helpers which are more specific.
Previously, PartitionTable was constructed using a Kernel::StorageDevice
making it only usable in the kernel. This commit adds a new constructor
that takes a Core::File instead, making it usable in userland as well.
This also adds the m_block_size field which stores the block size of the
underlying device obtained by calling StorageDevice::block_size() in the
kernel or by using the STORAGE_DEVICE_GET_BLOCK_SIZE ioctl in userland.
This avoids the need for an #ifdef every time block size is needed.
Everything in Kernel/Storage/Partition but DiskPartition has been moved
into LibPartiton. This makes the Partition directory unnecessary so
DiskPartition is moved up into Kernel/Storage.
This commit creates a new library LibPartition which will contain
partition related code sharable between Kernel and Userland and
includes DiskPartitionMetadata as the first shared class.
This adds a "temporary promises for the dynamic-linker" flag ('-d')
to the "pledge" utility.
Example usage:
pledge -d -p "stdio rpath" id
Without the '-d' flag, id would crash because the dynamic linker
requires 'prot_exec'.
When this flag is used and the program to be run is dynamically linked,
"pledge" adds promises that are required by the dynamic linker
to the promise set provided by the user.
The dynamic linker will later "give up" the pledge promises it no
longer requires.
Note that as part of this commit semaphore.cpp is excluded from the
DynamicLoader, as the dynamic loader does not build with pthread.cpp
which semaphore.cpp uses.
This helps ensure random pointers are not passed in as semaphores, but
more importantly once named semaphores are implemented, this will
ensure that random files are not used as semaphores.
