lkml.org 
[lkml]   [2020]   [Dec]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 1/3] x86/resctrl: Move setting task's active CPU in a mask into helpers
    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

    \
     
     \ /
      Last update: 2020-12-07 19:32    [W:4.856 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site