From: Yury Norov <yury.norov@gmail.com>
To: Pingfan Liu <kernelfans@gmail.com>
Cc: linux-kernel@vger.kernel.org,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Thomas Gleixner <tglx@linutronix.de>,
Steven Price <steven.price@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
"Jason A. Donenfeld" <Jason@zx2c4.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>
Subject: Re: [RFC 07/10] lib/cpumask: Introduce cpumask_not_dying_but()
Date: Mon, 22 Aug 2022 07:15:45 -0700 [thread overview]
Message-ID: <YwOPkc1cpoD/hs2D@yury-laptop> (raw)
In-Reply-To: <20220822021520.6996-8-kernelfans@gmail.com>
On Mon, Aug 22, 2022 at 10:15:17AM +0800, Pingfan Liu wrote:
> During cpu hot-removing, the dying cpus are still in cpu_online_mask.
> On the other hand, A subsystem will migrate its broker from the dying
> cpu to a online cpu in its teardown cpuhp_step.
>
> After enabling the teardown of cpus in parallel, cpu_online_mask can not
> tell those dying from the real online.
>
> Introducing a function cpumask_not_dying_but() to pick a real online
> cpu.
>
> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> Cc: Yury Norov <yury.norov@gmail.com>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Steven Price <steven.price@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
> Cc: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> To: linux-kernel@vger.kernel.org
> ---
> include/linux/cpumask.h | 3 +++
> kernel/cpu.c | 3 +++
> lib/cpumask.c | 18 ++++++++++++++++++
> 3 files changed, 24 insertions(+)
>
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index 0d435d0edbcb..d2033a239a07 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -317,6 +317,9 @@ unsigned int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
> return i;
> }
>
> +/* for parallel kexec reboot */
> +int cpumask_not_dying_but(const struct cpumask *mask, unsigned int cpu);
> +
> #define CPU_BITS_NONE \
> { \
> [0 ... BITS_TO_LONGS(NR_CPUS)-1] = 0UL \
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 90debbe28e85..771e344f8ff9 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -1282,6 +1282,9 @@ static void cpus_down_no_rollback(struct cpumask *cpus)
> struct cpuhp_cpu_state *st;
> unsigned int cpu;
>
> + for_each_cpu(cpu, cpus)
> + set_cpu_dying(cpu, true);
> +
> /* launch ap work one by one, but not wait for completion */
> for_each_cpu(cpu, cpus) {
> st = per_cpu_ptr(&cpuhp_state, cpu);
> diff --git a/lib/cpumask.c b/lib/cpumask.c
> index 8baeb37e23d3..6474f07ed87a 100644
> --- a/lib/cpumask.c
> +++ b/lib/cpumask.c
> @@ -7,6 +7,24 @@
> #include <linux/memblock.h>
> #include <linux/numa.h>
>
> +/* Used in parallel kexec-reboot cpuhp callbacks */
> +int cpumask_not_dying_but(const struct cpumask *mask,
> + unsigned int cpu)
> +{
> + unsigned int i;
> +
> + if (CONFIG_SHUTDOWN_NONBOOT_CPUS) {
Hmm... Would it even work? Anyways, the documentation says:
Within code, where possible, use the IS_ENABLED macro to convert a Kconfig
symbol into a C boolean expression, and use it in a normal C conditional:
.. code-block:: c
if (IS_ENABLED(CONFIG_SOMETHING)) {
...
}
> + cpumask_check(cpu);
> + for_each_cpu(i, mask)
> + if (i != cpu && !cpumask_test_cpu(i, cpu_dying_mask))
> + break;
> + return i;
> + } else {
> + return cpumask_any_but(mask, cpu);
> + }
> +}
> +EXPORT_SYMBOL(cpumask_not_dying_but);
I don't like how you create a dedicated function for a random
mask. Dying mask is nothing special, right? What you really
need is probably this:
cpumask_andnot_any_but(mask, cpu_dying_mask, cpu);
Now, if you still think it's worth that, you can add a trivial wrapper
for cpu_dying_mask. (But please pick some other name, because
'not dying but' sounds like a hangover description. :) )
Thanks,
Yury
> +
> /**
> * cpumask_next_wrap - helper to implement for_each_cpu_wrap
> * @n: the cpu prior to the place to search
> --
> 2.31.1
next prev parent reply other threads:[~2022-08-22 14:18 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-22 2:15 [RFC 00/10] arm64/riscv: Introduce fast kexec reboot Pingfan Liu
2022-08-22 2:15 ` [RFC 01/10] cpu/hotplug: Make __cpuhp_kick_ap() ready for async Pingfan Liu
2022-08-22 2:15 ` [RFC 02/10] cpu/hotplug: Compile smp_shutdown_nonboot_cpus() conditioned on CONFIG_SHUTDOWN_NONBOOT_CPUS Pingfan Liu
2022-08-22 2:15 ` [RFC 03/10] cpu/hotplug: Introduce fast kexec reboot Pingfan Liu
2022-08-22 2:15 ` [RFC 04/10] cpu/hotplug: Check the capability of kexec quick reboot Pingfan Liu
2022-08-22 2:15 ` [RFC 05/10] perf/arm-dsu: Make dsu_pmu_cpu_teardown() parallel Pingfan Liu
2022-08-22 2:15 ` [RFC 06/10] rcu/hotplug: Make rcutree_dead_cpu() parallel Pingfan Liu
2022-08-22 2:45 ` Paul E. McKenney
2022-08-23 1:50 ` Pingfan Liu
2022-08-23 3:01 ` Paul E. McKenney
2022-08-24 13:53 ` Pingfan Liu
2022-08-24 16:20 ` Paul E. McKenney
2022-08-24 17:26 ` Joel Fernandes
2022-08-24 19:21 ` Paul E. McKenney
2022-08-24 22:54 ` Joel Fernandes
2022-08-24 23:01 ` Paul E. McKenney
2022-08-31 16:15 ` Paul E. McKenney
2022-09-05 3:53 ` Pingfan Liu
2022-09-06 18:45 ` Paul E. McKenney
2022-08-22 18:08 ` Joel Fernandes
2022-08-23 1:56 ` Pingfan Liu
2022-08-23 3:14 ` Joel Fernandes
2022-08-24 13:38 ` Pingfan Liu
2022-08-24 13:44 ` Jason A. Donenfeld
2022-08-22 2:15 ` [RFC 07/10] lib/cpumask: Introduce cpumask_not_dying_but() Pingfan Liu
2022-08-22 14:15 ` Yury Norov [this message]
2022-08-23 7:29 ` Pingfan Liu
2022-08-22 2:15 ` [RFC 08/10] cpuhp: Replace cpumask_any_but(cpu_online_mask, cpu) Pingfan Liu
2022-08-22 2:15 ` [RFC 09/10] genirq/cpuhotplug: Ask migrate_one_irq() to migrate to a real online cpu Pingfan Liu
2022-08-22 2:15 ` [RFC 10/10] arm64: smp: Make __cpu_disable() parallel Pingfan Liu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YwOPkc1cpoD/hs2D@yury-laptop \
--to=yury.norov@gmail.com \
--cc=Jason@zx2c4.com \
--cc=andriy.shevchenko@linux.intel.com \
--cc=kernelfans@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@rasmusvillemoes.dk \
--cc=mark.rutland@arm.com \
--cc=sathyanarayanan.kuppuswamy@linux.intel.com \
--cc=steven.price@arm.com \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).