From: "Paul E. McKenney" <paulmck@kernel.org>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Uladzislau Rezki <urezki@gmail.com>,
Neeraj Upadhyay <quic_neeraju@quicinc.com>,
Boqun Feng <boqun.feng@gmail.com>,
Josh Triplett <josh@joshtriplett.org>,
Joel Fernandes <joel@joelfernandes.org>,
rcu@vger.kernel.org
Subject: Re: [PATCH 5/6] rcu/nocb: Allow empty "rcu_nocbs" kernel parameter
Date: Wed, 17 Nov 2021 11:46:05 -0800 [thread overview]
Message-ID: <20211117194605.GL641268@paulmck-ThinkPad-P17-Gen-1> (raw)
In-Reply-To: <20211117155637.363706-6-frederic@kernel.org>
On Wed, Nov 17, 2021 at 04:56:36PM +0100, Frederic Weisbecker wrote:
> If a user wants to boot without any CPU in offloaded mode initially but
> with the possibility to offload them later using cpusets, provide a way
> to simply pass an empty "rcu_nocbs" kernel parameter which will enforce
> the creation of dormant nocb kthreads.
>
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: Uladzislau Rezki <urezki@gmail.com>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Joel Fernandes <joel@joelfernandes.org>
> ---
> kernel/rcu/tree_nocb.h | 10 ++++++----
Could you please also update kernel-parameters.txt?
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
> index 1871f15b8472..3845f1885ffc 100644
> --- a/kernel/rcu/tree_nocb.h
> +++ b/kernel/rcu/tree_nocb.h
> @@ -66,14 +66,16 @@ static bool rcu_nocb_is_setup;
> static int __init rcu_nocb_setup(char *str)
> {
> alloc_bootmem_cpumask_var(&rcu_nocb_mask);
> - if (cpulist_parse(str, rcu_nocb_mask)) {
> - pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
> - cpumask_setall(rcu_nocb_mask);
> + if (*str == '=') {
> + if (cpulist_parse(++str, rcu_nocb_mask)) {
> + pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
> + cpumask_setall(rcu_nocb_mask);
> + }
Wouldn't "*str == '='" indicate that the parameter passed in was of
the form "rcu_nocbs==8"?
Or am I misreading the next_arg() function in lib/cmdline.c?
If I am reading it correctly, doesn't the test instead want to be
something of the form "if (str && *str)"?
Thanx, Paul
> }
> rcu_nocb_is_setup = true;
> return 1;
> }
> -__setup("rcu_nocbs=", rcu_nocb_setup);
> +__setup("rcu_nocbs", rcu_nocb_setup);
>
> static int __init parse_rcu_nocb_poll(char *arg)
> {
> --
> 2.25.1
>
next prev parent reply other threads:[~2021-11-17 19:46 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-17 15:56 [PATCH 0/6] rcu/nocb: Last prep work before cpuset interface Frederic Weisbecker
2021-11-17 15:56 ` [PATCH 1/6] rcu/nocb: Remove rdp from nocb list when de-offloaded Frederic Weisbecker
2021-11-17 18:53 ` Paul E. McKenney
2021-11-17 21:47 ` Frederic Weisbecker
2021-11-17 22:25 ` Paul E. McKenney
2021-11-17 15:56 ` [PATCH 2/6] rcu/nocb: Prepare nocb_cb_wait() to start with a non-offloaded rdp Frederic Weisbecker
2021-11-17 15:56 ` [PATCH 3/6] rcu/nocb: Optimize kthreads and rdp initialization Frederic Weisbecker
2021-11-17 15:56 ` [PATCH 4/6] rcu/nocb: Create nocb kthreads on all CPUs as long as the "rcu_nocb=" is passed Frederic Weisbecker
2021-11-17 19:27 ` Paul E. McKenney
2021-11-17 21:57 ` Frederic Weisbecker
2021-11-17 22:28 ` Paul E. McKenney
2021-11-17 15:56 ` [PATCH 5/6] rcu/nocb: Allow empty "rcu_nocbs" kernel parameter Frederic Weisbecker
2021-11-17 19:46 ` Paul E. McKenney [this message]
2021-11-17 22:02 ` Frederic Weisbecker
2021-11-17 22:33 ` Paul E. McKenney
2021-11-17 15:56 ` [PATCH 6/6] rcu/nocb: Merge rcu_spawn_cpu_nocb_kthread() and rcu_spawn_one_nocb_kthread() Frederic Weisbecker
2021-11-23 0:37 [PATCH 0/6] rcu/nocb: Last prep work before cpuset interface v2 Frederic Weisbecker
2021-11-23 0:37 ` [PATCH 5/6] rcu/nocb: Allow empty "rcu_nocbs" kernel parameter Frederic Weisbecker
2021-11-25 0:47 ` Paul E. McKenney
2021-11-25 0:55 ` Frederic Weisbecker
2021-11-25 1:02 ` Paul E. McKenney
2021-11-25 4:41 ` Yury Norov
2021-11-25 11:38 ` Andy Shevchenko
2021-11-25 13:28 ` Frederic Weisbecker
2021-11-25 15:06 ` Paul E. McKenney
2021-12-01 9:27 ` Neeraj Upadhyay
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