linux-kernel - Re: [PATCH 0/8] rcu: Fix expedited GP deadlock (and cleanup some nocb stuff)

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Message-ID: <0be847d6-804e-4f9d-9eb4-beee9efb6c78@paulmck-laptop>
Date:   Mon, 11 Dec 2023 08:38:59 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Neeraj Upadhyay <neeraj.upadhyay@....com>,
        Uladzislau Rezki <urezki@...il.com>,
        Zqiang <qiang.zhang1211@...il.com>, rcu <rcu@...r.kernel.org>
Subject: Re: [PATCH 0/8] rcu: Fix expedited GP deadlock (and cleanup some
 nocb stuff)

On Fri, Dec 08, 2023 at 11:05:37PM +0100, Frederic Weisbecker wrote:
> TREE04 can trigger a writer stall if run with memory pressure. This
> is due to a circular dependency between waiting for expedited grace
> period and polling on expedited grace period when workqueues go back
> to mayday serialization.
> 
> Here is a proposal fix.

The torture.sh "acceptance test" with KCSAN and --duration 30 ran
fine except for this in TREE09:

kernel/rcu/tree_nocb.h:1785:13: error: unused function '__call_rcu_nocb_wake' [-Werror,-Wunused-function]

My guess is that the declaration of __call_rcu_nocb_wake() in
kernel/rcu/tree.h needs an "#ifdef CONFIG_SMP", but you might have a
better fix.

						Thanx, Paul

> Frederic Weisbecker (8):
>   rcu/nocb: Make IRQs disablement symetric
>   rcu/nocb: Re-arrange call_rcu() NOCB specific code
>   rcu/exp: Fix RCU expedited parallel grace period kworker allocation
>     failure recovery
>   rcu/exp: Handle RCU expedited grace period kworker allocation failure
>   rcu: s/boost_kthread_mutex/kthread_mutex
>   rcu/exp: Make parallel exp gp kworker per rcu node
>   rcu/exp: Handle parallel exp gp kworkers affinity
>   rcu/exp: Remove rcu_par_gp_wq
> 
>  kernel/rcu/rcu.h         |   5 -
>  kernel/rcu/tree.c        | 222 +++++++++++++++++++++++++--------------
>  kernel/rcu/tree.h        |  12 +--
>  kernel/rcu/tree_exp.h    |  81 +++-----------
>  kernel/rcu/tree_nocb.h   |  38 ++++---
>  kernel/rcu/tree_plugin.h |  52 ++-------
>  6 files changed, 191 insertions(+), 219 deletions(-)
> 
> -- 
> 2.42.1
>