Crate thread

Available on crate feature threading only.

Multi-threading for Ariel OS.

Implements a scheduler based on fixed priorities and preemption. Within one priority level, threads are scheduled cooperatively. This means that there is no time slicing that would equally distribute CPU time among same-priority threads. Instead, you need to use yield_same() to explicitly yield to another thread with the same priority. If no thread is ready, the core is prompted to enter deep sleep until a next thread is ready.

Threads should be implemented using the ariel_os_macros::thread proc macro, which takes care of calling the necessary initialization methods and linking the thread function element it into the binary. A ThreadId between 0 and THREAD_COUNT is assigned to each thread in the order in which the threads are declared.

Optionally, the stacksize and a priority between 1 and SCHED_PRIO_LEVELS can be configured. By default, the stack size is 2048 bytes and priority is 1.

Synchronization

The threading module supports three basic synchronization primitives:

• Channel: synchronous (blocking) channel for sending data between threads
• Lock: basic locking object
• thread_flags: thread-flag implementation for signaling between threads

Modules

• sync
  Synchronization primitives.
• thread_flags
  Thread flags.

Structs

• CoreAffinitycore-affinity
  Affinity mask that defines on what cores a thread can be scheduled.
• CoreId
  ID of a physical core.
• RunqueueId
  Runqueue number.
• ThreadId

Constants

• CORE_COUNT
• IDLE_THREAD_STACK_SIZEmulti-core
• SCHED_PRIO_LEVELS
  The number of possible priority levels.
• THREAD_COUNT
  The maximum number of concurrent threads that can be created.

Traits

• Arguable
  Trait for types that fit into a single register.

Functions

• core_id
  Returns the id of the CPU that this thread is running on.
• create
  Low-level function to create a thread that runs func with arg.
• create_noarg
  Low-level function to create a thread without argument
• current_tid
  Returns the ThreadId of the currently active thread.
• get_priority
  Returns the priority of a thread.
• is_valid_tid
  Checks if a given ThreadId is valid.
• park
  Suspends/ pauses the current thread’s execution.
• set_priority
  Changes the priority of a thread.
• unpark
  Wakes up a thread and adds it to the runqueue.
• yield_same
  “Yields” to another thread with the same priority.