linux-kernel - [PATCH 00/11] rcu: Make rcu_core() safe in PREEMPT

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Date:   Thu, 30 Sep 2021 00:10:01 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     "Paul E . McKenney" <paulmck@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Boqun Feng <boqun.feng@...il.com>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Josh Triplett <josh@...htriplett.org>,
        Joel Fernandes <joel@...lfernandes.org>, rcu@...r.kernel.org
Subject: [PATCH 00/11] rcu: Make rcu_core() safe in PREEMPT_RT with NOCB + a few other fixes

PREEMPT_RT has made rcu_core() preemptible, making it unsafe against
concurrent NOCB (de-)offloading.

Thomas suggested to drop the local_lock() based solution and simply
check the offloaded state while context looks safe but that's not
enough. Here is a bit of rework.

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	rcu/rt

HEAD: aac1c58961446c731f2e989bd822ca1fd2659bad

Thanks,
	Frederic
---

Frederic Weisbecker (10):
      rcu/nocb: Make local rcu_nocb_lock_irqsave() safe against concurrent deoffloading
      rcu/nocb: Prepare state machine for a new step
      rcu/nocb: Invoke rcu_core() at the start of deoffloading
      rcu/nocb: Make rcu_core() callbacks acceleration (de-)offloading safe
      rcu/nocb: Check a stable offloaded state to manipulate qlen_last_fqs_check
      rcu/nocb: Use appropriate rcu_nocb_lock_irqsave()
      rcu/nocb: Limit number of softirq callbacks only on softirq
      rcu: Fix callbacks processing time limit retaining cond_resched()
      rcu: Apply callbacks processing time limit only on softirq
      rcu/nocb: Don't invoke local rcu core on callback overload from nocb kthread

Thomas Gleixner (1):
      rcu/nocb: Make rcu_core() callbacks acceleration preempt-safe


 include/linux/rcu_segcblist.h | 51 +++++++++++++++++++-------
 kernel/rcu/rcu_segcblist.c    | 10 ++---
 kernel/rcu/rcu_segcblist.h    |  7 ++--
 kernel/rcu/tree.c             | 85 ++++++++++++++++++++++++++++++-------------
 kernel/rcu/tree.h             | 16 +++++---
 kernel/rcu/tree_nocb.h        | 29 ++++++++++++---
 6 files changed, 136 insertions(+), 62 deletions(-)