In operating systems, write barrier is a mechanism for enforcing a particular ordering in a sequence of writes to a storage system in a computer system. For example, a write barrier in a file system is a mechanism (program logic) that ensures that in-memory file system state is written out to persistent storage in the correct order.
A write barrier in a garbage collector is a fragment of code emitted by the compiler immediately before every store operation to ensure that (e.g.) generational invariants are maintained. A write barrier in a memory system, also known as a memory barrier, is a hardware-specific compiler intrinsic that ensures that all preceding memory operations "happen before" all subsequent ones.
- Barriers and journaling filesystems (LWN.net, May 21, 2008)
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