Hello! Good turnout and some good questions here in Vancouver BC, please see below for rough notes. ;-) Thanx, Paul ------------------------------------------------------------------------ "Concurrency with tools/memory-model" Andrea Parri presenting. Rough notes of Q&A. o Want atomic bit operation. o But smp_read_barrier_depends() not there, so how to note pairing? A: Note the dependency as the other end of the pairing. o Speculation barriers, as in Spectre and Meltdown? A: This would require adding timing, not in the immediate future. o What ordering does system calls provide? A: None that we know of. Boqun: Userspace needs to explicitly provide the needed ordering when interacting with the kernel. Some architectures do provide full barriers, but not to be counted on. o Why herd7? A: Based on other formalizations -- note that herd7 had a number of hardware models. Paul: Plus the founder of the LKMM project is a co-author of herd, which might have had some effect. o Why not also model interrupts and NMIs? Promela and spin have been used for this. A: Cannot currently model them. You can emulated them with additional threads and locks, if you wish. Vincent Nimal and Lihao Liang have done some academic work on these topics.
