* Mathieu Desnoyers: >> Could it fall back to >> MEMBARRIER_CMD_GLOBAL instead? > > No. CMD_GLOBAL does not issue the required rseq fence used by the > algorithm discussed. Also, CMD_GLOBAL has quite a few other shortcomings: > it takes a while to execute, and is incompatible with nohz_full kernels. What about using sched_setcpu to move the current thread to the same CPU (and move it back afterwards)? Surely that implies the required sort of rseq barrier that MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ with MEMBARRIER_CMD_FLAG_CPU performs? That is possible even without membarrier, so I wonder why registration of intent is needed for MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ. > In order to make sure the programming model is the same for expedited > private/global plain/sync-core/rseq membarrier commands, we require that > each process perform a registration beforehand. Hmm. At least it's not possible to unregister again. But I think it would be really useful to have some of these barriers available without registration, possibly in a more expensive form. Thanks, Florian
