We're already holding a reference to the Runner prior to dispatching it
to the thread pool; we can pass that reference in rather than requiring
the thread pool to take a new reference to it.
There's no reason to wake up all the threads in a thread pool when one
item gets placed in the queue. Waking up one will serve the same
purpose and is significantly more efficient for thread pools with large
numbers of threads.
There's no reason nsThreadPool needs to use a reentrant monitor for
locking its event queue. Having it use a non-reentrant one should be
slightly more efficient, both in the general operation of the monitor,
and that we're not performing redundant locking in methods like
nsThreadPool::Run. This change also eliminates the only usage of
nsEventQueue::GetReentrantMonitor.
Clients of nsEventQueue don't always need fully reentrant monitors.
Let's account for that by having a base class templated on the monitor
type. This change also opens up the possibility of having the monitor
for the event queue not owned by the event queue itself, but by the
client class, which makes a lot more sense than the current design.
The comment here suggests that we might AddRef/Release, but we really do
no such thing. Let's deal with the transfer of ownership directly,
rather than going through nsCOMPtr. This change makes the code slightly
smaller, and it also makes later refactorings to pull the lock out of
this function easier to do, since we don't have to consider how to hold
the lock within the lifetime of the nsCOMPtr temporary.
The patch removes 455 occurrences of FAIL_ON_WARNINGS from moz.build files, and
adds 78 instances of ALLOW_COMPILER_WARNINGS. About half of those 78 are in
code we control and which should be removable with a little effort.
This is motivated by three separate but related problems:
1. Our concept of recursion depth is broken for things that run from AfterProcessNextEvent observers (e.g. Promises). We decrement the recursionDepth counter before firing observers, so a Promise callback running at the lowest event loop depth has a recursion depth of 0 (whereas a regular nsIRunnable would be 1). This is a problem because it's impossible to distinguish a Promise running after a sync XHR's onreadystatechange handler from a top-level event (since the former runs with depth 2 - 1 = 1, and the latter runs with just 1).
2. The nsIThreadObserver mechanism that is used by a lot of code to run "after" the current event is a poor fit for anything that runs script. First, the order the observers fire in is the order they were added, not anything fixed by spec. Additionally, running script can cause the event loop to spin, which is a big source of pain here (bholley has some nasty bug caused by this).
3. We run Promises from different points in the code for workers and main thread. The latter runs from XPConnect's nsIThreadObserver callbacks, while the former runs from a hardcoded call to run Promises in the worker event loop. What workers do is particularly problematic because it means we can't get the right recursion depth no matter what we do to nsThread.
The solve this, this patch does the following:
1. Consolidate some handling of microtasks and all handling of stable state from appshell and WorkerPrivate into CycleCollectedJSRuntime.
2. Make the recursionDepth counter only available to CycleCollectedJSRuntime (and its consumers) and remove it from the nsIThreadInternal and nsIThreadObserver APIs.
3. Adjust the recursionDepth counter so that microtasks run with the recursionDepth of the task they are associated with.
4. Introduce the concept of metastable state to replace appshell's RunBeforeNextEvent. Metastable state is reached after every microtask or task is completed. This provides the semantics that bent and I want for IndexedDB, where transactions autocommit at the end of a microtask and do not "spill" from one microtask into a subsequent microtask. This differs from appshell's RunBeforeNextEvent in two ways:
a) It fires between microtasks, which was the motivation for starting this.
b) It no longer ensures that we're at the same event loop depth in the native event queue. bent decided we don't care about this.
5. Reorder stable state to happen after microtasks such as Promises, per HTML. Right now we call the regular thread observers, including appshell, before the main thread observer (XPConnect), so stable state tasks happen before microtasks.
The bulk of this commit was generated by running:
run-clang-tidy.py \
-checks='-*,llvm-namespace-comment' \
-header-filter=^/.../mozilla-central/.* \
-fix
PostTimerEvent is only called by the timer thread, which is already able
to access private members of nsTimerImpl; there's no reason for
PostTimerEvent to be public.
GetTracedTask() is only called from nsTimerImpl itself, so it doesn't
need to be public. GetTLSTraceInfo() is called from the timer thread,
which has access to our private members already.
This is straightforward mapping of PR_LOG levels to their LogLevel
counterparts:
PR_LOG_ERROR -> LogLevel::Error
PR_LOG_WARNING -> LogLevel::Warning
PR_LOG_WARN -> LogLevel::Warning
PR_LOG_INFO -> LogLevel::Info
PR_LOG_DEBUG -> LogLevel::Debug
PR_LOG_NOTICE -> LogLevel::Debug
PR_LOG_VERBOSE -> LogLevel::Verbose
Instances of PRLogModuleLevel were mapped to a fully qualified
mozilla::LogLevel, instances of PR_LOG levels in #defines were mapped to a
fully qualified mozilla::LogLevel::* level, and all other instances were
mapped to us a shorter format of LogLevel::*.
Bustage for usage of the non-fully qualified LogLevel were fixed by adding
|using mozilla::LogLevel;| where appropriate.
This is straightforward mapping of PR_LOG levels to their LogLevel
counterparts:
PR_LOG_ERROR -> LogLevel::Error
PR_LOG_WARNING -> LogLevel::Warning
PR_LOG_WARN -> LogLevel::Warning
PR_LOG_INFO -> LogLevel::Info
PR_LOG_DEBUG -> LogLevel::Debug
PR_LOG_NOTICE -> LogLevel::Debug
PR_LOG_VERBOSE -> LogLevel::Verbose
Instances of PRLogModuleLevel were mapped to a fully qualified
mozilla::LogLevel, instances of PR_LOG levels in #defines were mapped to a
fully qualified mozilla::LogLevel::* level, and all other instances were
mapped to us a shorter format of LogLevel::*.
Bustage for usage of the non-fully qualified LogLevel were fixed by adding
|using mozilla::LogLevel;| where appropriate.
