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ac6 >> ac6-training >> Online Training >> Embedded Real-Time Systems >> Linux Real-Time and Multi-Core programming Download Catalog Download as PDF Write us Printable version

oRT1 Linux Real-Time and Multi-Core programming

Programming Linux real-time and multi-core systems, avoiding common pitfalls

formateur
Objectives
  • Discover the concepts of real time multitasking
  • Understand the specificities of multicore processors
  • Master concurrent programming
    • on the same processor
    • on a multiprocessor system
  • Understand real time constraints
    • Determinism
    • Preemption
    • Interruptions
  • Interactions with processor architecture features
    • Cache
    • Pipeline
    • I/O optimizations
    • Multicore and Hyperthreading
  • Debug real time applications
  • Understand the structure of a real time kernel
Labs are conducted QEMU ARM-based board
Prerequisite
  • Good C programming skills (see our L2 course)
  • Basic understanding of processor architecture
Course environment
  • Theoretical course
    • PDF course material (in English)
    • Course dispensed using the Teams video-conferencing system
    • The trainer to answer trainees’ questions during the training and provide technical and pedagogical assistance through the Teams video-conferencing system
  • Practical activities
    • Practical activities represent from 40% to 50% of course duration
    • One Online Linux PC per trainee for the practical activities
    • The trainer has access to trainees’ Online PCs for technical and pedagogical assistance.
    • Eclipse environment and GCC compiler
  • Downloadable preconfigured virtual machine for post-course practical activities.
Duration
  • Total: 30 hours
  • 5 sessions, 5 hours each (excluding break time)
  • From 40% to 50% of training time is devoted to practical activities
  • Some Labs may be completed between sessions and are checked by the trainer on the next session

First Session
Introduction to real time
  • Base real time concepts
  • The real time constraints
  • Multi-task and real-time
  • Multi-core and Hyperthreading
Exercise:  Prepare the environment
Exercise:  Create a simple context switch routine
Thread safe data structures
  • Need for specific data structures
  • Thread safe data structures
    • Linked lists (simple or double links)
    • Circular lists
    • FIFOs
    • Stacks
  • Data structure integrity proofs
    • Assertions
    • Pre and post-conditions
Exercise:  Build a general purpose thread safe doubly linked list
Memory management
  • Memory management algorithms
    • Buddy system
    • Best fit
    • First fit
    • Pool management
  • Memory management errors
    • memory leaks
    • using unallocated/deallocated memory
    • stack monitoring
Exercise:  Write a simple, thread safe, buddy system memory manager
Exercise:  Write a generic, multi-level, memory manager
Exercise:  Enhance the memory manager for memory error detection
Exercise:  Enhance the context switching infrastructure to monitor stack use
Second Session
Elements of a real time system
  • Tasks and task descriptors
    • Content of the task descriptor
    • Lists of task descriptors
  • Context switch
  • Task scheduling and preemption
    • Tick based or tickless scheduling
  • Scheduling systems and schedulability proofs
    • Fixed priority scheduling
    • RMA and EDF scheduling
    • Adaptive scheduling
Exercise:  Write a simple, fixed priority, scheduler
Interrupt management in real time systems
  • Need for interrupts in a real time system
    • Time interrupts
    • Device interrupts
  • Level or Edge interrupts
  • Hardware and software acknowledge
  • Interrupt vectoring
  • Interrupts and scheduling
Exercise:  Write a basic interrupt manager
Exercise:  Extend the scheduler to also support real-time round-robin scheduling
Multicore interactions
  • Cache coherency
    • Snooping basics
    • Snoop Control Unit: cache-to-cache transfers
    • MOESI state machine
  • Memory Ordering and Coherency
    • Out-of-order accesses
    • Memory ordering
    • Memory barriers
    • DMA data coherency
  • Multicore data access
    • Read-Modify-Write instructions
    • Linked-Read/Conditional-Write
  • Multicore synchronization
    • Spinlocks
    • Inter-Processor Interrupts
Exercise:  Writing a spinlock implementation
Third Session
Multicore scheduling
  • Multicore scheduling
    • Assigning interrupts to processors
    • Multi-core scheduling
  • Multicore optimization
    • Cache usage optimization
    • Avoiding false sharing
    • Avoiding cache spilling
Exercise:  Study of a multi-core scheduler
Synchronization primitives
  • Waiting and waking up tasks
  • Semaphores
  • Mutual exclusion
    • Spinlocks and interrupt masking
    • Mutexes or semaphores
    • Recursive and non-recursive mutexes
    • The priority inversion problem
    • Priority inheritance (the automagic answer)
    • Priority ceiling (the design centric answer)
  • Mutexes and condition variables
  • Mailboxes
Exercise:  Implement Semaphores by direct interaction with the scheduler
Exercise:  Implement the mutex mechanism
Exercise:  Check proper nesting of mutexes and recursive/non-recursive use
Exercise:  Implement a priority ceiling mechanism
Exercise:  Add Condition variable support to the mutex mechanism
Fourth Session
Avoiding sequencing problems
  • The various sequencing problems
    • Uncontrolled parallel access
    • Deadlocks
    • Livelocks
    • Starvation
Exercise:  The producer-consumer problem, illustrating (and avoiding) concurrent access problems
Exercise:  The philosophers dinner problem, illustrating (and avoiding) deadlock, livelock and starvation
Working with Pthreads
  • The pthread standard
    • threads
    • mutexes and condition variables
    • Thread local storage
  • POSIX semaphores
  • Scheduling
    • context switches
    • scheduling policies (real-time, traditional)
    • preemption
Exercise:  Solve the classic readers-writers problem with POSIX threads
Exercise:  Maintain per-thread static data for the readers-writers problem
Fifth Session
Multi-tasking in the Linux kernel
  • Kernel memory management
    • "buddy" and "slab" memory allocation algorithms
  • Kernel task handling
  • Linux kernel threads
    • creation
    • termination
  • Concurrent kernel programming
    • atomic operations
    • spinlocks
    • read/write locks
    • semaphores and read/write semaphores
    • mutexes
    • sequential locks
    • read-copy-update
    • hardware spinlock
  • Basic thread synchronization
    • waiting queues
    • completion events
  • Hardware clocks
    • clockevents
  • Software clocks
    • delayed execution
    • kernel timers
    • high resolution timers
Exercise:  Create a kernel-mode execution barrier using kernel synchronization primitives
Exercise:  Create a kernel event synchronization object, using basic synchronization primitives
Asymmetric multiprocessing
  • AMP overview
    • Architecture
    • Shared memory
    • Challenges comparing to SMP
  • Inter-processor communication
  • OpenAMP framework
    • Remoteproc
    • rpmsg
Exercise:  Sending messages between AMP cores demonstration