From: Borislav Petkov <bp@alien8.de>
To: Reinette Chatre <reinette.chatre@intel.com>
Cc: tglx@linutronix.de, fenghua.yu@intel.com, tony.luck@intel.com,
kuo-lang.tseng@intel.com, shakeelb@google.com,
valentin.schneider@arm.com, mingo@redhat.com, babu.moger@amd.com,
james.morse@arm.com, hpa@zytor.com, x86@kernel.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH 1/3] x86/resctrl: Move setting task's active CPU in a mask into helpers
Date: Mon, 7 Dec 2020 19:29:12 +0100 [thread overview]
Message-ID: <20201207182912.GF20489@zn.tnic> (raw)
In-Reply-To: <77973e75a10bf7ef9b33c664544667deee9e1a8e.1607036601.git.reinette.chatre@intel.com>
On Thu, Dec 03, 2020 at 03:25:48PM -0800, Reinette Chatre wrote:
> From: Fenghua Yu <fenghua.yu@intel.com>
>
> The code of setting the CPU on which a task is running in a CPU mask is
> moved into a couple of helpers.
Pls read section "2) Describe your changes" in
Documentation/process/submitting-patches.rst for more details.
More specifically:
"Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
to do frotz", as if you are giving orders to the codebase to change
its behaviour."
> The new helper task_on_cpu() will be reused shortly.
"reused shortly"? I don't think so.
>
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
> Reviewed-by: Tony Luck <tony.luck@intel.com>
> Cc: stable@vger.kernel.org
Fixes?
I guess the same commit from the other two:
Fixes: e02737d5b826 ("x86/intel_rdt: Add tasks files")
?
> ---
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 47 +++++++++++++++++++-------
> 1 file changed, 34 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 6f4ca4bea625..68db7d2dec8f 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -525,6 +525,38 @@ static void rdtgroup_remove(struct rdtgroup *rdtgrp)
> kfree(rdtgrp);
> }
>
> +#ifdef CONFIG_SMP
> +/* Get the CPU if the task is on it. */
> +static bool task_on_cpu(struct task_struct *t, int *cpu)
> +{
> + /*
> + * This is safe on x86 w/o barriers as the ordering of writing to
> + * task_cpu() and t->on_cpu is reverse to the reading here. The
> + * detection is inaccurate as tasks might move or schedule before
> + * the smp function call takes place. In such a case the function
> + * call is pointless, but there is no other side effect.
> + */
> + if (t->on_cpu) {
> + *cpu = task_cpu(t);
Why have an I/O parameter when you can make it simply:
static int task_on_cpu(struct task_struct *t)
{
if (t->on_cpu)
return task_cpu(t);
return -1;
}
> +
> + return true;
> + }
> +
> + return false;
> +}
> +
> +static void set_task_cpumask(struct task_struct *t, struct cpumask *mask)
> +{
> + int cpu;
> +
> + if (mask && task_on_cpu(t, &cpu))
> + cpumask_set_cpu(cpu, mask);
And that you can turn into:
if (!mask)
return;
cpu = task_on_cpu(t);
if (cpu < 0)
return;
cpumask_set_cpu(cpu, mask);
Readable and simple.
Hmm?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2020-12-07 18:29 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 23:25 [PATCH 0/3] x86/resctrl: Fix a few issues in moving a task to a resource group Reinette Chatre
2020-12-03 23:25 ` [PATCH 1/3] x86/resctrl: Move setting task's active CPU in a mask into helpers Reinette Chatre
2020-12-07 18:29 ` Borislav Petkov [this message]
2020-12-07 21:24 ` Reinette Chatre
2020-12-08 9:49 ` Borislav Petkov
2020-12-08 16:35 ` Reinette Chatre
2020-12-09 16:47 ` James Morse
2020-12-10 0:21 ` Reinette Chatre
2020-12-03 23:25 ` [PATCH 2/3] x86/resctrl: Update PQR_ASSOC MSR synchronously when moving task to resource group Reinette Chatre
2020-12-09 16:51 ` James Morse
2020-12-10 0:22 ` Reinette Chatre
2020-12-11 20:46 ` Valentin Schneider
2020-12-14 18:41 ` Reinette Chatre
2020-12-16 17:41 ` Valentin Schneider
2020-12-16 18:26 ` Reinette Chatre
2020-12-17 10:39 ` Valentin Schneider
2020-12-03 23:25 ` [PATCH 3/3] x86/resctrl: Don't move a task to the same " Reinette Chatre
2020-12-11 20:46 ` [PATCH 0/3] x86/resctrl: Fix a few issues in moving a task to a " Valentin Schneider
2020-12-14 18:38 ` Reinette Chatre
2020-12-16 17:41 ` Valentin Schneider
2020-12-16 18:26 ` Reinette Chatre
2020-12-17 12:19 ` [PATCH 4/3] x86/intel_rdt: Apply READ_ONCE/WRITE_ONCE to task_struct .rmid & .closid Valentin Schneider
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