[PATCH V11 07/17] riscv: qspinlock: Introduce qspinlock param for command line

[Waiman Long]

On 9/14/23 03:32, Leonardo Bras wrote:
> On Tue, Sep 12, 2023 at 09:08:34AM +0800, Guo Ren wrote:
>> On Mon, Sep 11, 2023 at 11:34 PM Waiman Long <longman at redhat.com> wrote:
>>> On 9/10/23 04:29, guoren at kernel.org wrote:
>>>> From: Guo Ren <guoren at linux.alibaba.com>
>>>>
>>>> Allow cmdline to force the kernel to use queued_spinlock when
>>>> CONFIG_RISCV_COMBO_SPINLOCKS=y.
>>>>
>>>> Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
>>>> Signed-off-by: Guo Ren <guoren at kernel.org>
>>>> ---
>>>>    Documentation/admin-guide/kernel-parameters.txt |  2 ++
>>>>    arch/riscv/kernel/setup.c                       | 16 +++++++++++++++-
>>>>    2 files changed, 17 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>>>> index 7dfb540c4f6c..61cacb8dfd0e 100644
>>>> --- a/Documentation/admin-guide/kernel-parameters.txt
>>>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>>>> @@ -4693,6 +4693,8 @@
>>>>                        [KNL] Number of legacy pty's. Overwrites compiled-in
>>>>                        default number.
>>>>
>>>> +     qspinlock       [RISCV] Force to use qspinlock or auto-detect spinlock.
>>>> +
>>>>        qspinlock.numa_spinlock_threshold_ns=   [NUMA, PV_OPS]
>>>>                        Set the time threshold in nanoseconds for the
>>>>                        number of intra-node lock hand-offs before the
>>>> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
>>>> index a447cf360a18..0f084f037651 100644
>>>> --- a/arch/riscv/kernel/setup.c
>>>> +++ b/arch/riscv/kernel/setup.c
>>>> @@ -270,6 +270,15 @@ static void __init parse_dtb(void)
>>>>    }
>>>>
>>>>    #ifdef CONFIG_RISCV_COMBO_SPINLOCKS
>>>> +bool enable_qspinlock_key = false;
>>> You can use __ro_after_init qualifier for enable_qspinlock_key. BTW,
>>> this is not a static key, just a simple flag. So what is the point of
>>> the _key suffix?
>> Okay, I would change it to:
>> bool enable_qspinlock_flag __ro_after_init = false;
> IIUC, this bool / flag is used in a single file, so it makes sense for it
> to be static. Being static means it does not need to be initialized to
> false, as it's standard to zero-fill this areas.
>
> Also, since it's a bool, it does not need to be called _flag.
>
> I would go with:
>
> static bool enable_qspinlock __ro_after_init;

I actually was thinking about the same suggestion to add static. Then I 
realized that the flag was also used in another file in a later patch. 
Of course, if it turns out that this flag is no longer needed outside of 
this file, it should be static.

Cheers,
Longman