linux-kernel - Re: [PATCH 0/7] rcu: Fix expedited GP deadlock

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Date: Tue, 16 Jan 2024 11:11:53 -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>, rcu <rcu@...r.kernel.org>
Subject: Re: [PATCH 0/7] rcu: Fix expedited GP deadlock

On Fri, Jan 12, 2024 at 04:46:14PM +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.
> 
> Changes since v2 (no functional changes, just renames and reorganization):
> 
> _ Move nocb cleanups to their own series
> _ Rename can_queue parameter to use_worker [2/7]
> _ Better explain the rename of the mutex [3/7]
> _ New commit with just code move to ease review [4/7]
> _ Comment declaration of the new rnp->exp_worker field [5/7]
> 
> Thanks.

Hearing no objections, queued for testing and further review,
thank you!

							Thanx, Paul

> Frederic Weisbecker (7):
>   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: Move expedited kthread worker creation functions above
>     rcutree_prepare_cpu()
>   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        | 175 +++++++++++++++++++++++++++------------
>  kernel/rcu/tree.h        |  11 ++-
>  kernel/rcu/tree_exp.h    |  78 +++--------------
>  kernel/rcu/tree_plugin.h |  52 ++----------
>  5 files changed, 142 insertions(+), 179 deletions(-)
> 
> -- 
> 2.34.1
> 
>