[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZkypxKBSPPGIo9Se@pathway.suse.cz>
Date: Tue, 21 May 2024 16:03:48 +0200
From: Petr Mladek <pmladek@...e.com>
To: John Ogness <john.ogness@...utronix.de>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
"Paul E. McKenney" <paulmck@...nel.org>,
Frederic Weisbecker <frederic@...nel.org>,
Neeraj Upadhyay <quic_neeraju@...cinc.com>,
Joel Fernandes <joel@...lfernandes.org>,
Josh Triplett <josh@...htriplett.org>,
Boqun Feng <boqun.feng@...il.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
Zqiang <qiang.zhang1211@...il.com>, rcu@...r.kernel.org
Subject: Re: [PATCH printk v5 29/30] rcu: Mark emergency sections in rcu
stalls
On Thu 2024-05-02 23:44:38, John Ogness wrote:
> Mark emergency sections wherever multiple lines of
> rcu stall information are generated. In an emergency
> section the CPU will not perform console output for the
> printk() calls. Instead, a flushing of the console
> output is triggered when exiting the emergency section.
> This allows the full message block to be stored as
> quickly as possible in the ringbuffer.
>
> --- a/kernel/rcu/tree_exp.h
> +++ b/kernel/rcu/tree_exp.h
> @@ -612,6 +616,7 @@ static void synchronize_rcu_expedited_wait(void)
> }
> pr_cont("\n");
> }
> + nbcon_cpu_emergency_flush();
It would make more sense to do the flush inside the cycle after each
dump_cpu_task(). Something like:
rcu_for_each_leaf_node(rnp) {
for_each_leaf_node_possible_cpu(rnp, cpu) {
mask = leaf_node_cpu_bit(rnp, cpu);
if (!(READ_ONCE(rnp->expmask) & mask))
continue;
preempt_disable(); // For smp_processor_id() in dump_cpu_task().
dump_cpu_task(cpu);
preempt_enable();
+ nbcon_cpu_emergency_flush();
}
rcu_exp_print_detail_task_stall_rnp(rnp);
}
Or maybe, it is limited onto to few CPUs by rcu_for_each_leaf_node(rnp)?
> rcu_for_each_leaf_node(rnp) {
> for_each_leaf_node_possible_cpu(rnp, cpu) {
> mask = leaf_node_cpu_bit(rnp, cpu);
Otherwise, it looks good to me.
Best Regards,
Petr
Powered by blists - more mailing lists