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In computer science, the thundering herd problem occurs when a large number of processes or threads waiting for an event are awakened when that event occurs, but only one process is able to handle the event. When the processes wake up, they will each try to handle the event, but only one will win.
Read-copy-update insertion procedure. A thread allocates a structure with three fields, then sets the global pointer gptr to point to this structure.. A key property of RCU is that readers can access a data structure even when it is in the process of being updated: RCU updaters cannot block readers or force them to retry their accesses.
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 ...
Sending cache is changed in S and the requesting cache is set R/F (in read miss the "ownership" is always taken by the last requesting cache) – shared intervention. – In all the other cases the data is supplied by the memory and the requesting cache is set S (V). Data stored in MM and only in one cache in E (R) state.
Contention: some threads/processes have to wait until a lock (or a whole set of locks) is released. If one of the threads holding a lock dies, stalls, blocks, or enters an infinite loop, other threads waiting for the lock may wait indefinitely until the computer is power cycled.
In computer science, a readers–writer (single-writer lock, [1] a multi-reader lock, [2] a push lock, [3] or an MRSW lock) is a synchronization primitive that solves one of the readers–writers problems. An RW lock allows concurrent access for read-only operations, whereas
This was a spurious wakeup, some other thread occurred // first and caused the condition to become false again, and we must // wait again. wait (m, cv); // Temporarily prevent any other thread on any core from doing // operations on m or cv. // release(m) // Atomically release lock "m" so other // // code using this concurrent data // // can ...
Now P3 releases the lock, incrementing now_serving to 2, allowing P2 to acquire it (Row 6). While P2 has the lock, P4 attempts to acquire it, gets a my_ticket value of 3, increments next_ticket to 4, and must wait since now_serving is still 2 (Row 7). When P2 releases the lock, it increments now_serving to 3, allowing P4 to get it (Row 8).