This implementation does not use locking or condition variables
internally; it's purely based on atomics and futexes.
Notably, concurrent sem_wait() and sem_post() calls can run *completely
in parallel* without slowing each other down, as long as there are empty
slots for them all to succeed without blocking.
Additionally, sem_wait() never executes an atomic operation with release
ordering, and sem_post() never executes an atomic operation with acquire
ordering (unless you count the syscall). This means the compiler and the
hardware are free to reorder code *into* the critical section.
This implementation features a fast path for pthread_cond_signal() and
pthread_cond_broadcast() for the case there's no thread waiting, and
does not exhibit the "thundering herd" issue in
pthread_cond_broadcast().
Fixes https://github.com/SerenityOS/serenity/issues/8432
This is a private function that locks the lock much like the regular
pthread_mutex_lock(), but causes the corresponding unlock operation to
always assume there may be other waiters. This is useful in case some
waiters are made to wait on the mutex's futex directly, without going
through pthread_mutex_lock(). This is going to be used by the condition
variable implementation in the next commit.
pthread_mutex is now an actual "sleeping" mutex, and not just a
spinlock! It still has a fast path that only uses atomics and (in the
successful case) returns immediately without sleeping. In case of
contention, it calls futex_wait(), which lets the kernel scheduler put
this thread to sleep, *and* lets it know exactly when to consider
scheduling it again.
These are convinient wrappers over the most used futex operations.
futex_wait() also does some smarts for timeout and clock handling.
Use the new futex_wait() instead of a similar private helper in
LibPthread.
This fixes a build issue introduced in 23d66fe, where the compiler
statically detected that that mismatching new and delete operators were
used.
Clang generates a warning for this, for the reasons described in the
comment in `AK/kmalloc.cpp`, but GCC does not.
Besides moving the allocator functions into a `.cpp` file, declarations
in `AK/kmalloc.cpp` were reordered to have imports at the top, in order
to make the code more readable.
Piano is an old application that predates AudioServer. For this reason,
it was architected to directly talk to the soundcard via the /dev/audio
device. This caused multiple problems including simultaneous playback
issues, no ability to change volume/mute for Piano and more.
This change moves Piano to use AudioServer like any well-behaved audio
application :^) The track processing and IPC communication is moved to
the main thread because IPC doesn't like multi-threading. For this, the
new AudioPlayerLoop class is utilized that should evolve into the
DSP->AudioServer interface in the future.
Because Piano's CPU utilization has gotten so low (about 3-6%), the UI
update loop is switched back to render at exactly 60fps.
This is an important commit on the road to #6528.
async_enqueue() is a wrapper over the async_enqueue_buffer() call
to AudioServer. This allows users to asyncronously enqueue audio
samples, when the program requires non-blocking audio streaming.
This also makes ClientConnection use east-const everywhere.
We don't know what is a good time to wait after an audio buffer fails to
be processed by AudioServer. However, it seems like decreasing the wait
time to 10ms after such a failure should improve latency and has not
caused issues in my testing. After all, 10ms is quite some time in audio
sample magnitudes.
This change enforces that paths passed to
VFS::validate_path_against_process_veil are absolute and do not contain
any '..' or '.' parts. We should VERIFY here instead of returning EINVAL
since the code that calls this should resolve non-canonical paths before
calling this function.
Previously, Custody::absolute_path() was called for every call to
validate_path_against_process_veil(). For processes that don't have a
veil, the path is not used by the function. This means that it is
unnecessarily generated. This introduces an overload to
validate_path_against_process_veil(), which takes a Custody const& and
only generates the absolute path if it there is actually a veil and it
is thus needed.
This patch results in a speed up of Assistant's file system cache
building by around 16 percent.
We need to move the result out of the BackgroundAction object before
posting the completion callback as there is a chance the
BackgroundAction instance gets freed before the event loop runs our
callback.
Fixes#7641
If calling the executor function throws an exception, the return value
of `vm.call()` will be an empty value, which we then passed as an
argument to the reject function, which is incorrect - what it actually
needs is the exception value. This stems from a misunderstanding of the
spec I had at the time of implementing this - in their case, the
exception value is part of the completion record returned by Call().
This error was previously masked as we would use a fallback
(`value_or(js_undefined())` for the empty value argument, but that was
removed in 57f7e6e.
Fixes#8447.
As the name implies (and the spec confirms), this is only ever going to
be an object or "nothing", or "undefined" in the spec. By taking this
literally and updating a check to check for `is_undefined()`, we
introduced a bug - the value was still initialized as an empty value.
Instead, use a pointer to an Object - either we have one, or we don't.
Fixes#8448.
Non-RangeError exceptions can be thrown by user implementations of
valueOf (which are called by to_index), and the specification
disallows changing the type of the thrown error.
Previously it was not doing so, and some code relied on this not being
the case.
In particular, set_caption, set_t_head and set_t_foot in
HTMLTableElement relied on this. This commit is not here to fix this,
so I added an assertion to make it equivalent to a reference for now.
Nodes implementing the adoption steps can modify the passed in
document, for example HTMLTemplateElement does so to adopt it's
contents into the new document.
This will be used in HTMLTemplateElement later to clone template
contents.
This makes the clone functions non-const in the process, as the cloning
steps can have side effects.
It was directly creating a new Element object instead of creating the
appropriate element.
For example, document.body.cloneNode(true) would return an Element
instead of an HTMLBodyElement.
