Hi Paul, This series applies on top of "hazptr: handle NULL address in hazptr_detach" you have in your rcu dev tree.
This first patch addresses a race identified by Boqun Feng in the two-phase wildcard scheme. (no change since the last series) Patches 2-3 are prerequisites for using ptr_eq() in the 4th patch. Those were discussed at length in a prior version of hazard pointer patches. Since the last series, I have modified patch 2 to take into account feedback from Linus: There is now a x86-specific implementation of ptr_eq, an asm-generic fallback, and both sit in newly introduced "ptreq.h" headers. The documentation is moved to linux/ptreq.h, which includes asm/ptreq.h. This reuses all the usual mechanisms for arch-specific implementation with asm-generic fallback. Patch 4 introduces a "try acquire" helper to allow the fast path to not rely on wildcards, while keeping the wildcard forward progress guarantees in the acquire slow path, used on fast path failure. Thanks, Mathieu Mathieu Desnoyers (4): hazptr: Fix two-phase hazptr_synchronize race with detach ptreq.h: Introduce ptr_eq() to preserve address dependency Documentation: RCU: Refer to ptr_eq() hazptr: Introduce "try acquire" fast path, fallback to overflow list Cc: Paul E. McKenney <[email protected]> Cc: Boqun Feng <[email protected]> Cc: Bradley Morgan <[email protected]> Cc: Gary Guo <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: Lian Wang <[email protected]> Cc: Kunwu Chan <[email protected]> Documentation/RCU/rcu_dereference.rst | 38 +++++++- arch/x86/include/asm/ptreq.h | 16 +++ include/asm-generic/Kbuild | 1 + include/asm-generic/ptreq.h | 16 +++ include/linux/hazptr.h | 48 +++++---- include/linux/ptreq.h | 63 ++++++++++++ kernel/hazptr.c | 135 +++++++++++++++----------- 7 files changed, 237 insertions(+), 80 deletions(-) create mode 100644 arch/x86/include/asm/ptreq.h create mode 100644 include/asm-generic/ptreq.h create mode 100644 include/linux/ptreq.h -- 2.43.0
