From: Michael Ellerman <mpe@ellerman•id.au>
To: Joel Stanley <joel@jms•id.au>, linuxppc-dev@lists•ozlabs.org
Cc: ego@linux•ibm.com
Subject: Re: [PATCH] powerpc: Warn about use of smt_snooze_delay
Date: Tue, 30 Jun 2020 11:22:29 +1000 [thread overview]
Message-ID: <87366d8i0a.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20200625100349.2408899-1-joel@jms.id.au>
Joel Stanley <joel@jms•id.au> writes:
> It's not done anything for a long time. Save the percpu variable, and
> emit a warning to remind users to not expect it to do anything.
>
> Signed-off-by: Joel Stanley <joel@jms•id.au>
> ---
> arch/powerpc/kernel/sysfs.c | 41 +++++++++++++------------------------
> 1 file changed, 14 insertions(+), 27 deletions(-)
>
> diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
> index 571b3259697e..530ae92bc46d 100644
> --- a/arch/powerpc/kernel/sysfs.c
> +++ b/arch/powerpc/kernel/sysfs.c
> @@ -32,29 +32,25 @@
>
> static DEFINE_PER_CPU(struct cpu, cpu_devices);
>
> -/*
> - * SMT snooze delay stuff, 64-bit only for now
> - */
> -
> #ifdef CONFIG_PPC64
>
> -/* Time in microseconds we delay before sleeping in the idle loop */
> -static DEFINE_PER_CPU(long, smt_snooze_delay) = { 100 };
> +/*
> + * Snooze delay has not been hooked up since 3fa8cad82b94 ("powerpc/pseries/cpuidle:
> + * smt-snooze-delay cleanup.") and has been broken even longer. As was foretold in
> + * 2014:
> + *
> + * "ppc64_util currently utilises it. Once we fix ppc64_util, propose to clean
> + * up the kernel code."
> + *
> + * At some point in the future this code should be removed.
> + */
>
> static ssize_t store_smt_snooze_delay(struct device *dev,
> struct device_attribute *attr,
> const char *buf,
> size_t count)
> {
> - struct cpu *cpu = container_of(dev, struct cpu, dev);
> - ssize_t ret;
> - long snooze;
> -
> - ret = sscanf(buf, "%ld", &snooze);
> - if (ret != 1)
> - return -EINVAL;
> -
> - per_cpu(smt_snooze_delay, cpu->dev.id) = snooze;
> + WARN_ON_ONCE("smt_snooze_delay sysfs file has no effect\n");
We shouldn't have user-triggerable WARNs.
I think this should just be a pr_warn_ratelimited(), maybe including
current->comm & pid.
cheers
prev parent reply other threads:[~2020-06-30 1:22 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-25 10:03 [PATCH] powerpc: Warn about use of smt_snooze_delay Joel Stanley
2020-06-25 10:29 ` Christophe Leroy
2020-06-25 20:38 ` Tyrel Datwyler
2020-06-29 10:42 ` Gautham R Shenoy
2020-06-30 1:05 ` Joel Stanley
2020-06-30 1:22 ` Michael Ellerman [this message]
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=87366d8i0a.fsf@mpe.ellerman.id.au \
--to=mpe@ellerman$(echo .)id.au \
--cc=ego@linux$(echo .)ibm.com \
--cc=joel@jms$(echo .)id.au \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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