Hello! This RFC series provides an NMI-safe SRCU reader API in the guise of srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe(). A given srcu_struct structure must use either the traditional srcu_read_lock() and srcu_read_unlock() API or the new _nmisafe() API: Mixing and matching is not permitted. So much so that kernels built with CONFIG_PROVE_RCU=y will complain if you try it. The reason for this restriction is that I have yet to find a use case that is not a accident waiting to happen. And if free intermixing were permitted, it is pretty much a given that someone somewhere will get confused and use srcu_read_lock_nmisafe() within NMI handlers and srcu_read_lock() elsewhere, which will not (repeat, NOT) provide NMI safety. The series is as follows: 1. Convert ->srcu_lock_count and ->srcu_unlock_count to atomic. 2. Create and srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe(). 3. Check for consistent per-CPU per-srcu_struct NMI safety. 4. Check for consistent global per-srcu_struct NMI safety. Thanx, Paul ------------------------------------------------------------------------ b/include/linux/srcu.h | 37 ++++++++++++++++++++ b/include/linux/srcutiny.h | 11 ++++++ b/include/linux/srcutree.h | 4 +- b/kernel/rcu/Kconfig | 3 + b/kernel/rcu/rcutorture.c | 11 ++++-- b/kernel/rcu/srcutree.c | 24 ++++++------- include/linux/srcu.h | 4 +- include/linux/srcutiny.h | 4 +- include/linux/srcutree.h | 12 +++++- kernel/rcu/srcutree.c | 82 +++++++++++++++++++++++++++++++++++++++------ 10 files changed, 160 insertions(+), 32 deletions(-)
