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

Paul E. McKenney
2023-12-11T16:39:00Z

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
>