linux-kernel - [RFC PATCH 0/8] rcu/sched: Fix ignored rescheduling after rcu_eqs

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Date:   Sat,  9 Jan 2021 03:05:28 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        "Paul E . McKenney" <paulmck@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, stable@...r.kernel.org
Subject: [RFC PATCH 0/8] rcu/sched: Fix ignored rescheduling after rcu_eqs_enter() v3

(This was [PATCH 0/4] sched/idle: Fix missing need_resched() checks after rcu_idle_enter() v2)

I initially followed Peterz review but eventually I tried a different
approach. Instead of handling the late wake up from rcu_idle_enter(),
I've split the delayed rcuog wake up and moved it right before
the last generic need_resched() check, it makes more sense and we don't
need to fiddle with cpuidle core and drivers anymore. It's also less
error prone.

I also fixed the nohz_full case and (hopefully) the guest case.

And this comes with debugging to prevent from that pattern to happen
again.

Only lightly tested so far.

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	sched/idle-v3

HEAD: d95fc510e804a5c4658a823ff12d9caba1d906c7

Thanks,
	Frederic
---

Frederic Weisbecker (8):
      rcu: Remove superfluous rdp fetch
      rcu: Pull deferred rcuog wake up to rcu_eqs_enter() callers
      rcu/nocb: Perform deferred wake up before last idle's need_resched() check
      rcu/nocb: Trigger self-IPI on late deferred wake up before user resume
      entry: Explicitly flush pending rcuog wakeup before last rescheduling points
      sched: Report local wake up on resched blind zone within idle loop
      entry: Report local wake up on resched blind zone while resuming to user
      timer: Report ignored local enqueue in nohz mode


 include/linux/rcupdate.h |  2 ++
 include/linux/sched.h    | 11 ++++++++
 kernel/entry/common.c    | 10 ++++++++
 kernel/rcu/tree.c        | 27 ++++++++++++++++++--
 kernel/rcu/tree.h        |  2 +-
 kernel/rcu/tree_plugin.h | 30 +++++++++++++++-------
 kernel/sched/core.c      | 66 +++++++++++++++++++++++++++++++++++++++++++++++-
 kernel/sched/idle.c      |  6 +++++
 kernel/sched/sched.h     |  3 +++
 9 files changed, 144 insertions(+), 13 deletions(-)