linux-kernel - [PATCH v2 0/4] rcu, arm64: PREEMPT

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Date:   Sat,  7 Aug 2021 01:58:03 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        rcu@...r.kernel.org, linux-rt-users@...r.kernel.org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Steven Price <steven.price@....com>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: [PATCH v2 0/4] rcu, arm64: PREEMPT_RT fixlets

Hi folks,

this is v2 of:

  https://lore.kernel.org/lkml/20210721115118.729943-1-valentin.schneider@arm.com/

respun from Frederic and Paul's helpful feedback. Tested atop v5.14-rc4-rt6 with
the v1 patches reverted. There, commit 

  d76e0926d835 ("rcu/nocb: Use the rcuog CPU's ->nocb_timer")

prevents the NOCB offload warning from firing if there are no NOCB CPUs (which
is sensible). Adding a single NOCB CPU brings the warning back, which patch 3
fixes.

Note that patches 2 & 4 are already in v5.14-rc4-rt6, but still apply against
mainline.

Revisions
=========

v1 -> v2
++++++++

o Rebased and tested against v5.14-rc4-rt6
o Picked rcutorture patch from
  https://lore.kernel.org/lkml/20210803225437.3612591-2-valentin.schneider@arm.com/
o Added a local_lock to protect NOCB offload state under PREEMPT_RT (Frederic,
  Paul)

Valentin Schneider (4):
  rcutorture: Don't disable softirqs with preemption disabled when
    PREEMPT_RT
  sched: Introduce is_pcpu_safe()
  rcu/nocb: Protect NOCB state via local_lock() under PREEMPT_RT
  arm64: mm: Make arch_faults_on_old_pte() check for migratability

 arch/arm64/include/asm/pgtable.h |  2 +-
 include/linux/sched.h            | 10 ++++
 kernel/rcu/rcutorture.c          |  2 +
 kernel/rcu/tree.c                |  4 ++
 kernel/rcu/tree.h                |  4 ++
 kernel/rcu/tree_plugin.h         | 82 ++++++++++++++++++++++++++++----
 6 files changed, 94 insertions(+), 10 deletions(-)

--
2.25.1