linux-kernel - [PATCH 0/4] rcu: Fix PF_IDLE related issues, part. 1

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Message-Id: <20231019233543.1243121-1-frederic@kernel.org>
Date:   Fri, 20 Oct 2023 01:35:39 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Neeraj Upadhyay <neeraj.upadhyay@....com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Uladzislau Rezki <urezki@...il.com>, rcu <rcu@...r.kernel.org>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Zqiang <qiang.zhang1211@...il.com>,
        Lai Jiangshan <jiangshanlai@...il.com>
Subject: [PATCH 0/4] rcu: Fix PF_IDLE related issues, part. 1

The modification of PF_IDLE semantics lately to fix a bug in rcutiny
eventually introduced new bugs in RCU-tasks. This series revert that
PF_IDLE modification and fix rcutiny in an alternate way.

More issues need to be fixed in RCU-tasks:

* The boot code preceding the idle entry is included in this
  quiescent state. Especially after the completion of kthreadd_done
  after which init/1 can launch userspace concurrently. The window
  is tiny before PF_IDLE is set but it exists.

* Similarly, the boot code preceding the idle entry on secondary
  CPUs is wrongly accounted as RCU tasks quiescent state.

And those will be fixed separetely.

Frederic Weisbecker (4):
  softirq: Rename __raise_softirq_irqoff() to raise_softirq_no_wake()
  softirq: Introduce raise_ksoftirqd_irqoff()
  rcu: Make tiny RCU use ksoftirqd to trigger a QS from idle
  Revert "kernel/sched: Modify initial boot task idle setup"

 block/blk-mq.c            |  2 +-
 include/linux/interrupt.h |  3 ++-
 kernel/rcu/tiny.c         | 21 +++++++++++++-----
 kernel/sched/core.c       |  2 +-
 kernel/sched/idle.c       |  1 -
 kernel/softirq.c          | 45 +++++++++++++++++++++++++--------------
 lib/irq_poll.c            |  4 ++--
 net/core/dev.c            |  8 +++----
 8 files changed, 55 insertions(+), 31 deletions(-)

-- 
2.34.1