https://nalar.dev/tags/membarrier/ Recent content in Membarrier on Nalar Hugo en-us Wed, 23 Sep 2026 00:00:00 +0000 https://nalar.dev/membarrier-private-expedited-orders-userspace-memory-across-threads/ Wed, 23 Sep 2026 00:00:00 +0000 https://nalar.dev/membarrier-private-expedited-orders-userspace-memory-across-threads/ <p>Linux <code>membarrier()</code> can move part of a synchronization cost from a frequently executed path to a less frequent coordination path. With <code>MEMBARRIER_CMD_PRIVATE_EXPEDITED</code>, one thread asks the kernel to establish a memory-ordering point across the running threads in the same process. The caller pays for the system call when coordination is needed instead of requiring every fast-path execution to carry an explicit hardware memory barrier.</p> <p>This is narrower than a general thread rendezvous. <code>membarrier()</code> does not run an application callback on sibling threads, does not wait for application-level acknowledgements, and does not turn ordinary data races into valid synchronization. Its contract concerns ordering of userspace memory accesses around the barrier.</p>