Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 378 insertions, 0 deletions

diff --git a/xpcom/rust/moz_task/src/lib.rs b/xpcom/rust/moz_task/src/lib.rs
new file mode 100644
index 0000000000..2f0c0cfd0a
--- /dev/null
+++ b/xpcom/rust/moz_task/src/lib.rs
@@ -0,0 +1,378 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! This module wraps XPCOM threading functions with Rust functions
+//! to make it safer and more convenient to call the XPCOM functions.
+//! It also provides the Task trait and TaskRunnable struct,
+//! which make it easier to dispatch tasks to threads.
+
+mod dispatcher;
+pub use dispatcher::{dispatch_background_task, dispatch_local, dispatch_onto, RunnableBuilder};
+mod event_loop;
+mod executor;
+pub use executor::{
+    spawn, spawn_blocking, spawn_local, spawn_onto, spawn_onto_blocking, AsyncTask, TaskBuilder,
+};
+
+// Expose functions intended to be used only in gtest via this module.
+// We don't use a feature gate here to stop the need to compile all crates that
+// depend upon `moz_task` twice.
+pub mod gtest_only {
+    pub use crate::event_loop::spin_event_loop_until;
+}
+
+use nserror::nsresult;
+use nsstring::{nsACString, nsCString};
+use std::{ffi::CStr, marker::PhantomData, mem, ptr};
+use xpcom::{
+    getter_addrefs,
+    interfaces::{nsIEventTarget, nsIRunnable, nsISerialEventTarget, nsISupports, nsIThread},
+    AtomicRefcnt, RefCounted, RefPtr, XpCom,
+};
+
+extern "C" {
+    fn NS_GetCurrentThreadRust(result: *mut *const nsIThread) -> nsresult;
+    fn NS_GetMainThreadRust(result: *mut *const nsIThread) -> nsresult;
+    fn NS_IsMainThread() -> bool;
+    fn NS_NewNamedThreadWithDefaultStackSize(
+        name: *const nsACString,
+        result: *mut *const nsIThread,
+        event: *const nsIRunnable,
+    ) -> nsresult;
+    fn NS_IsOnCurrentThread(target: *const nsIEventTarget) -> bool;
+    fn NS_ProxyReleaseISupports(
+        name: *const libc::c_char,
+        target: *const nsIEventTarget,
+        doomed: *const nsISupports,
+        always_proxy: bool,
+    );
+    fn NS_CreateBackgroundTaskQueue(
+        name: *const libc::c_char,
+        target: *mut *const nsISerialEventTarget,
+    ) -> nsresult;
+    fn NS_DispatchBackgroundTask(event: *const nsIRunnable, flags: u32) -> nsresult;
+}
+
+pub fn get_current_thread() -> Result<RefPtr<nsIThread>, nsresult> {
+    getter_addrefs(|p| unsafe { NS_GetCurrentThreadRust(p) })
+}
+
+pub fn get_main_thread() -> Result<RefPtr<nsIThread>, nsresult> {
+    getter_addrefs(|p| unsafe { NS_GetMainThreadRust(p) })
+}
+
+pub fn is_main_thread() -> bool {
+    unsafe { NS_IsMainThread() }
+}
+
+// There's no OS requirement that thread names be static, but dynamic thread
+// names tend to conceal more than they reveal when processing large numbers of
+// crash reports.
+pub fn create_thread(name: &'static str) -> Result<RefPtr<nsIThread>, nsresult> {
+    getter_addrefs(|p| unsafe {
+        NS_NewNamedThreadWithDefaultStackSize(&*nsCString::from(name), p, ptr::null())
+    })
+}
+
+pub fn is_on_current_thread(target: &nsIEventTarget) -> bool {
+    unsafe { NS_IsOnCurrentThread(target) }
+}
+
+/// Creates a queue that runs tasks on the background thread pool. The tasks
+/// will run in the order they're dispatched, one after the other.
+pub fn create_background_task_queue(
+    name: &'static CStr,
+) -> Result<RefPtr<nsISerialEventTarget>, nsresult> {
+    getter_addrefs(|p| unsafe { NS_CreateBackgroundTaskQueue(name.as_ptr(), p) })
+}
+
+/// Dispatches a one-shot runnable to an event target, like a thread or a
+/// task queue, with the given options.
+///
+/// This function leaks the runnable if dispatch fails.
+///
+/// # Safety
+///
+/// As there is no guarantee that the runnable is actually `Send + Sync`, we
+/// can't know that it's safe to dispatch an `nsIRunnable` to any
+/// `nsIEventTarget`.
+pub unsafe fn dispatch_runnable(
+    runnable: &nsIRunnable,
+    target: &nsIEventTarget,
+    options: DispatchOptions,
+) -> Result<(), nsresult> {
+    // NOTE: DispatchFromScript performs an AddRef on `runnable` which is
+    // why this function leaks on failure.
+    target
+        .DispatchFromScript(runnable, options.flags())
+        .to_result()
+}
+
+/// Dispatches a one-shot task runnable to the background thread pool with the
+/// given options. The task may run concurrently with other background tasks.
+/// If you need tasks to run in a specific order, please create a background
+/// task queue using `create_background_task_queue`, and dispatch tasks to it
+/// instead.
+///
+/// This function leaks the runnable if dispatch fails. This avoids a race where
+/// a runnable can be destroyed on either the original or target thread, which
+/// is important if the runnable holds thread-unsafe members.
+///
+/// ### Safety
+///
+/// As there is no guarantee that the runnable is actually `Send + Sync`, we
+/// can't know that it's safe to dispatch an `nsIRunnable` to any
+/// `nsIEventTarget`.
+pub unsafe fn dispatch_background_task_runnable(
+    runnable: &nsIRunnable,
+    options: DispatchOptions,
+) -> Result<(), nsresult> {
+    // This eventually calls the non-`already_AddRefed<nsIRunnable>` overload of
+    // `nsIEventTarget::Dispatch` (see xpcom/threads/nsIEventTarget.idl#20-25),
+    // which adds an owning reference and leaks if dispatch fails.
+    NS_DispatchBackgroundTask(runnable, options.flags()).to_result()
+}
+
+/// Options to control how task runnables are dispatched.
+#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
+pub struct DispatchOptions(u32);
+
+impl Default for DispatchOptions {
+    #[inline]
+    fn default() -> Self {
+        DispatchOptions(nsIEventTarget::DISPATCH_NORMAL)
+    }
+}
+
+impl DispatchOptions {
+    /// Creates a blank set of options. The runnable will be dispatched using
+    /// the default mode.
+    #[inline]
+    pub fn new() -> Self {
+        DispatchOptions::default()
+    }
+
+    /// Indicates whether or not the dispatched runnable may block its target
+    /// thread by waiting on I/O. If `true`, the runnable may be dispatched to a
+    /// dedicated thread pool, leaving the main pool free for CPU-bound tasks.
+    #[inline]
+    pub fn may_block(self, may_block: bool) -> DispatchOptions {
+        const FLAG: u32 = nsIEventTarget::DISPATCH_EVENT_MAY_BLOCK;
+        if may_block {
+            DispatchOptions(self.flags() | FLAG)
+        } else {
+            DispatchOptions(self.flags() & !FLAG)
+        }
+    }
+
+    /// Specifies that the dispatch is occurring from a running event that was
+    /// dispatched to the same event target, and that event is about to finish.
+    ///
+    /// A thread pool can use this as an optimization hint to not spin up
+    /// another thread, since the current thread is about to become idle.
+    ///
+    /// Setting this flag is unsafe, as it may only be used from the target
+    /// event target when the event is about to finish.
+    #[inline]
+    pub unsafe fn at_end(self, may_block: bool) -> DispatchOptions {
+        const FLAG: u32 = nsIEventTarget::DISPATCH_AT_END;
+        if may_block {
+            DispatchOptions(self.flags() | FLAG)
+        } else {
+            DispatchOptions(self.flags() & !FLAG)
+        }
+    }
+
+    /// Returns the set of bitflags to pass to `DispatchFromScript`.
+    #[inline]
+    fn flags(self) -> u32 {
+        self.0
+    }
+}
+
+/// A task represents an operation that asynchronously executes on a target
+/// thread, and returns its result to the original thread.
+///
+/// # Alternatives
+///
+/// This trait is no longer necessary for basic tasks to be dispatched to
+/// another thread with a callback on the originating thread. `moz_task` now has
+/// a series of more rust-like primitives which can be used instead. For
+/// example, it may be preferable to use the async executor over `Task`:
+///
+/// ```ignore
+/// // Spawn a task onto the background task pool, and capture the result of its
+/// // execution.
+/// let bg_task = moz_task::spawn("Example", async move {
+///     do_background_work(captured_state)
+/// });
+///
+/// // Spawn another task on the calling thread which will await on the result
+/// // of the async operation, and invoke a non-Send callback. This task won't
+/// // be awaited on, so needs to be `detach`-ed.
+/// moz_task::spawn_local("Example", async move {
+///     callback.completed(bg_task.await);
+/// })
+/// .detach();
+/// ```
+///
+/// If no result is needed, the task returned from `spawn` may be also detached
+/// directly.
+pub trait Task {
+    // FIXME: These could accept `&mut`.
+    fn run(&self);
+    fn done(&self) -> Result<(), nsresult>;
+}
+
+pub struct TaskRunnable {
+    name: &'static str,
+    task: Box<dyn Task + Send + Sync>,
+}
+
+impl TaskRunnable {
+    // XXX: Fixme: clean up this old API. (bug 1744312)
+    pub fn new(
+        name: &'static str,
+        task: Box<dyn Task + Send + Sync>,
+    ) -> Result<TaskRunnable, nsresult> {
+        Ok(TaskRunnable { name, task })
+    }
+
+    pub fn dispatch(self, target: &nsIEventTarget) -> Result<(), nsresult> {
+        self.dispatch_with_options(target, DispatchOptions::default())
+    }
+
+    pub fn dispatch_with_options(
+        self,
+        target: &nsIEventTarget,
+        options: DispatchOptions,
+    ) -> Result<(), nsresult> {
+        // Perform `task.run()` on a background thread.
+        let task = self.task;
+        let handle = TaskBuilder::new(self.name, async move {
+            task.run();
+            task
+        })
+        .options(options)
+        .spawn_onto(target);
+
+        // Run `task.done()` on the starting thread once the background thread
+        // is done with the task.
+        spawn_local(self.name, async move {
+            let task = handle.await;
+            let _ = task.done();
+        })
+        .detach();
+        Ok(())
+    }
+
+    pub fn dispatch_background_task_with_options(
+        self,
+        options: DispatchOptions,
+    ) -> Result<(), nsresult> {
+        // Perform `task.run()` on a background thread.
+        let task = self.task;
+        let handle = TaskBuilder::new(self.name, async move {
+            task.run();
+            task
+        })
+        .options(options)
+        .spawn();
+
+        // Run `task.done()` on the starting thread once the background thread
+        // is done with the task.
+        spawn_local(self.name, async move {
+            let task = handle.await;
+            let _ = task.done();
+        })
+        .detach();
+        Ok(())
+    }
+}
+
+pub type ThreadPtrHandle<T> = RefPtr<ThreadPtrHolder<T>>;
+
+/// A Rust analog to `nsMainThreadPtrHolder` that wraps an `nsISupports` object
+/// with thread-safe refcounting. The holder keeps one reference to the wrapped
+/// object that's released when the holder's refcount reaches zero.
+pub struct ThreadPtrHolder<T: XpCom + 'static> {
+    ptr: *const T,
+    marker: PhantomData<T>,
+    name: &'static CStr,
+    owning_thread: RefPtr<nsIThread>,
+    refcnt: AtomicRefcnt,
+}
+
+unsafe impl<T: XpCom + 'static> Send for ThreadPtrHolder<T> {}
+unsafe impl<T: XpCom + 'static> Sync for ThreadPtrHolder<T> {}
+
+unsafe impl<T: XpCom + 'static> RefCounted for ThreadPtrHolder<T> {
+    unsafe fn addref(&self) {
+        self.refcnt.inc();
+    }
+
+    unsafe fn release(&self) {
+        let rc = self.refcnt.dec();
+        if rc == 0 {
+            // Once the holder's count reaches zero, release the wrapped
+            // object...
+            if !self.ptr.is_null() {
+                // The holder can be released on any thread. If we're on the
+                // owning thread, we can release the object directly. Otherwise,
+                // we need to post a proxy release event to release the object
+                // on the owning thread.
+                if is_on_current_thread(&self.owning_thread) {
+                    (*self.ptr).release()
+                } else {
+                    NS_ProxyReleaseISupports(
+                        self.name.as_ptr(),
+                        self.owning_thread.coerce(),
+                        self.ptr as *const T as *const nsISupports,
+                        false,
+                    );
+                }
+            }
+            // ...And deallocate the holder.
+            mem::drop(Box::from_raw(self as *const Self as *mut Self));
+        }
+    }
+}
+
+impl<T: XpCom + 'static> ThreadPtrHolder<T> {
+    /// Creates a new owning thread pointer holder. Returns an error if the
+    /// thread manager has shut down. Panics if `name` isn't a valid C string.
+    pub fn new(name: &'static CStr, ptr: RefPtr<T>) -> Result<RefPtr<Self>, nsresult> {
+        let owning_thread = get_current_thread()?;
+        // Take ownership of the `RefPtr`. This does _not_ decrement its
+        // refcount, which is what we want. Once we've released all references
+        // to the holder, we'll release the wrapped `RefPtr`.
+        let raw: *const T = &*ptr;
+        mem::forget(ptr);
+        unsafe {
+            let boxed = Box::new(ThreadPtrHolder {
+                name,
+                ptr: raw,
+                marker: PhantomData,
+                owning_thread,
+                refcnt: AtomicRefcnt::new(),
+            });
+            Ok(RefPtr::from_raw(Box::into_raw(boxed)).unwrap())
+        }
+    }
+
+    /// Returns the wrapped object's owning thread.
+    pub fn owning_thread(&self) -> &nsIThread {
+        &self.owning_thread
+    }
+
+    /// Returns the wrapped object if called from the owning thread, or
+    /// `None` if called from any other thread.
+    pub fn get(&self) -> Option<&T> {
+        if is_on_current_thread(&self.owning_thread) && !self.ptr.is_null() {
+            unsafe { Some(&*self.ptr) }
+        } else {
+            None
+        }
+    }
+}