Messages in this thread | | | Subject | Re: [PATCH 1/3] x86/resctrl: Move setting task's active CPU in a mask into helpers | From | Reinette Chatre <> | Date | Mon, 7 Dec 2020 13:24:51 -0800 |
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Hi Borislav,
Thank you very much for your review.
On 12/7/2020 10:29 AM, Borislav Petkov wrote: > 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.
How about: "Move the setting of the CPU on which a task is running in a CPU mask into a couple of helpers.
There is no functional change. This is a preparatory change for the fix in the following patch from where the Fixes tag is copied."
> >> >> 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") > > ?
Correct. I will add it. The addition to the commit message above aims to explain a Fixes tag to a patch with no functional changes.
>> --- >> 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? >
Will do. Thank you very much.
Reinette
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