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Thread safe, MT-safe: Use a mutex for every single resource to guarantee the thread to be free of race conditions when those resources are accessed by multiple threads simultaneously. Thread safety guarantees usually also include design steps to prevent or limit the risk of different forms of deadlocks , as well as optimizations to maximize ...
This code shows the effect of false sharing. It creates an increasing number of threads from one thread to the number of physical threads in the system. Each thread sequentially increments one byte of a cache line, which as a whole is shared among all threads. The higher the level of contention between threads, the longer each increment takes.
Note that this only covers physical memory addresses. Trying to access an undefined virtual memory address is generally considered to be a segmentation fault rather than a bus error, though if the MMU is separate, the processor cannot tell the difference.
At the level of code errors, this occurs when the program writes to part of its own code segment or the read-only portion of the data segment, as these are loaded by the OS into read-only memory. Here is an example of ANSI C code that will generally cause a segmentation fault on platforms with memory protection.
Concurrent data structures are significantly more difficult to design and to verify as being correct than their sequential counterparts. The primary source of this additional difficulty is concurrency, exacerbated by the fact that threads must be thought of as being completely asynchronous: they are subject to operating system preemption, page faults, interrupts, and so on.
An algorithm is lock-free if, when the program threads are run for a sufficiently long time, at least one of the threads makes progress (for some sensible definition of progress). All wait-free algorithms are lock-free. In particular, if one thread is suspended, then a lock-free algorithm guarantees that the remaining threads can still make ...
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The memory model specifies synchronization barriers that are established via special, well-defined synchronization operations such as acquiring a lock by entering a synchronized block or method. The memory model stipulates that changes to the values of shared variables only need to be made visible to other threads when such a synchronization ...