Messages in this thread | | | Date | Mon, 7 Dec 2020 19:29:12 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH 1/3] x86/resctrl: Move setting task's active CPU in a mask into helpers |
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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
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