From: Frederic Weisbecker <frederic@kernel.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Neeraj Upadhyay <neeraj.upadhyay@amd.com>,
Uladzislau Rezki <urezki@gmail.com>,
Zqiang <qiang.zhang1211@gmail.com>, rcu <rcu@vger.kernel.org>
Subject: Re: [PATCH 0/8] rcu: Fix expedited GP deadlock (and cleanup some nocb stuff)
Date: Mon, 11 Dec 2023 21:04:04 +0100 [thread overview]
Message-ID: <ZXdrNJFCaXAFMITp@localhost.localdomain> (raw)
In-Reply-To: <0be847d6-804e-4f9d-9eb4-beee9efb6c78@paulmck-laptop>
Le Mon, Dec 11, 2023 at 08:38:59AM -0800, Paul E. McKenney a écrit :
> 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.
Could be because if CONFIG_RCU_NO_CB_CPU=n, the function is only called
(though as dead code) from rcutree_migrate_callbacks() which in turn only
exists if CONFIG_HOTPLUG_CPU=y.
Something like that then:
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 35f7af331e6c..e1ff53d5084c 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -445,6 +445,8 @@ static void rcu_qs(void);
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
+static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
+ unsigned long flags);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
static int rcu_print_task_exp_stall(struct rcu_node *rnp);
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
@@ -466,8 +468,6 @@ static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
unsigned long j, bool lazy);
static void call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *head,
rcu_callback_t func, unsigned long flags, bool lazy);
-static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
- unsigned long flags);
static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level);
static bool do_nocb_deferred_wakeup(struct rcu_data *rdp);
static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
next prev parent reply other threads:[~2023-12-11 20:04 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-08 22:05 [PATCH 0/8] rcu: Fix expedited GP deadlock (and cleanup some nocb stuff) Frederic Weisbecker
2023-12-08 22:05 ` [PATCH 1/8] rcu/nocb: Make IRQs disablement symetric Frederic Weisbecker
2023-12-13 13:01 ` Neeraj upadhyay
2023-12-08 22:05 ` [PATCH 2/8] rcu/nocb: Re-arrange call_rcu() NOCB specific code Frederic Weisbecker
2023-12-08 22:05 ` [PATCH 3/8] rcu/exp: Fix RCU expedited parallel grace period kworker allocation failure recovery Frederic Weisbecker
2023-12-12 16:04 ` Kalesh Singh
2023-12-12 16:10 ` Kalesh Singh
2023-12-08 22:05 ` [PATCH 4/8] rcu/exp: Handle RCU expedited grace period kworker allocation failure Frederic Weisbecker
2023-12-12 16:14 ` Kalesh Singh
2023-12-08 22:05 ` [PATCH 5/8] rcu: s/boost_kthread_mutex/kthread_mutex Frederic Weisbecker
2023-12-08 22:05 ` [PATCH 6/8] rcu/exp: Make parallel exp gp kworker per rcu node Frederic Weisbecker
2023-12-08 22:05 ` [PATCH 7/8] rcu/exp: Handle parallel exp gp kworkers affinity Frederic Weisbecker
2023-12-08 22:05 ` [PATCH 8/8] rcu/exp: Remove rcu_par_gp_wq Frederic Weisbecker
2023-12-11 16:38 ` [PATCH 0/8] rcu: Fix expedited GP deadlock (and cleanup some nocb stuff) Paul E. McKenney
2023-12-11 20:04 ` Frederic Weisbecker [this message]
2023-12-11 21:39 ` Paul E. McKenney
2023-12-12 13:34 ` Frederic Weisbecker
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