Here is a v5 of my Hazard Pointers series. I know Boqun has a use case for it for lockdep.
This new version has those significant changes since v4: - Fold scheduler integration. - Actually set ctx slot to backup slot on context switch. - Remove CONFIG_PREEMPT_HAZPTR config option. - Use per-cpu ctx pointers for context switch slot tracking rather than per-task lists. This accelerates the hazptr acquire/release fast-path. - Guarantee scan forward progress with two-lists scheme. - Reimplement the hazptr acquire with a temporary wildcard to eliminate a dependency on the addr_p load, likely to cause a pipeline stall due to the needed memory barrier. This simplifies the algorithm, removes the need for pointer re-load + comparison, and is expected to be faster on some architectures. - Reduce number of percpu slots to 4, introduce a hazptr_slot_item struct to contain both the slot and ctx pointers. Reducing number of slots to 4 makes sure all the slot and ctx pointers fit in a single cache line. - Rebased on v7.0-rc1. Feedback is welcome, Thanks, Mathieu Cc: Nicholas Piggin <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Sebastian Andrzej Siewior <[email protected]> Cc: "Paul E. McKenney" <[email protected]> Cc: Will Deacon <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Boqun Feng <[email protected]> Cc: Alan Stern <[email protected]> Cc: John Stultz <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Joel Fernandes <[email protected]> Cc: Josh Triplett <[email protected]> Cc: Uladzislau Rezki <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Lai Jiangshan <[email protected]> Cc: Zqiang <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Waiman Long <[email protected]> Cc: Mark Rutland <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: [email protected] Cc: Mateusz Guzik <[email protected]> Cc: Jonas Oberhauser <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Mathieu Desnoyers (2): hazptr: Implement Hazard Pointers hazptr: Add refscale test include/linux/hazptr.h | 197 +++++++++++++++++++++++++++++++++ init/main.c | 2 + kernel/Makefile | 2 +- kernel/hazptr.c | 242 +++++++++++++++++++++++++++++++++++++++++ kernel/rcu/refscale.c | 43 ++++++++ kernel/sched/core.c | 2 + 6 files changed, 487 insertions(+), 1 deletion(-) create mode 100644 include/linux/hazptr.h create mode 100644 kernel/hazptr.c -- 2.39.5
