linux-kernel - Re: [PATCH v5] sched/psi: fix memory barrier without comment warnings

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Message-ID: <CAJuCfpE+LSd7hogwGnLMT5y831unLjCpS3DpOASgphDFxDjGJw@mail.gmail.com>
Date: Mon, 14 Oct 2024 14:06:36 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Pintu Kumar <quic_pintu@...cinc.com>
Cc: hannes@...xchg.org, peterz@...radead.org, mingo@...hat.com, 
	juri.lelli@...hat.com, vincent.guittot@...aro.org, dietmar.eggemann@....com, 
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de, vschneid@...hat.com, 
	christophe.jaillet@...adoo.fr, linux-kernel@...r.kernel.org, joe@...ches.com, 
	skhan@...uxfoundation.org, pintu.ping@...il.com
Subject: Re: [PATCH v5] sched/psi: fix memory barrier without comment warnings

On Sun, Oct 6, 2024 at 1:29 AM Pintu Kumar <quic_pintu@...cinc.com> wrote:
>
> These warnings were reported by checkpatch.
> Fix them with minor changes.
> No functional changes.
>
> WARNING: memory barrier without comment
> +       t = smp_load_acquire(trigger_ptr);
>
> WARNING: memory barrier without comment
> +       smp_store_release(&seq->private, new);
>
> Signed-off-by: Pintu Kumar <quic_pintu@...cinc.com>

Acked-by: Suren Baghdasaryan <surenb@...gle.com>

>
> ---
> Changes in V5:
> Corrected api name and missing () in comments as suggested by Christophe JAILLET.
> V4: https://lore.kernel.org/all/a8393bc0-6f56-4e40-b971-4a837cf28323@wanadoo.fr/
> Changes in V4:
> Added () in comment as well suggested by Christophe JAILLET.
> V3: https://lore.kernel.org/all/00aeb243-3d47-42be-b52c-08b39c5fef07@wanadoo.fr/
> Changes in V3:
> Removed signature of Joe as requested. No other change.
> V2: https://lore.kernel.org/all/CAOuPNLi1mUKW_vv0E6Ynzvdw_rHvCye+nAf2bWv6Qj9A8ofX1g@mail.gmail.com/
> Changes in V2:
> Retain printk_deferred warnings as suggested by Joe Perches.
> V1: https://lore.kernel.org/all/a848671f803ba2b4ab14b0f7b09f0f53a8dd1c4b.camel@perches.com/
> ---
>  kernel/sched/psi.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index 020d58967d4e..907fa3830c8e 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -1474,6 +1474,7 @@ __poll_t psi_trigger_poll(void **trigger_ptr,
>         if (static_branch_likely(&psi_disabled))
>                 return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI;
>
> +       /* Pairs with the smp_store_release() in psi_write() */
>         t = smp_load_acquire(trigger_ptr);
>         if (!t)
>                 return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI;
> @@ -1557,6 +1558,7 @@ static ssize_t psi_write(struct file *file, const char __user *user_buf,
>                 return PTR_ERR(new);
>         }
>
> +       /* Pairs with the smp_load_acquire() in psi_trigger_poll() */
>         smp_store_release(&seq->private, new);
>         mutex_unlock(&seq->lock);
>
> --
> 2.17.1
>