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

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Message-ID: <20241006082926.20647-1-quic_pintu@quicinc.com>
Date: Sun, 6 Oct 2024 13:59:26 +0530
From: Pintu Kumar <quic_pintu@...cinc.com>
To: <hannes@...xchg.org>, <surenb@...gle.com>, <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>
CC: <joe@...ches.com>, <skhan@...uxfoundation.org>, <pintu.ping@...il.com>,
        Pintu Kumar <quic_pintu@...cinc.com>
Subject: [PATCH v5] sched/psi: fix memory barrier without comment warnings

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>

---
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