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(unknown []) by gzsmtp4 (Coremail) with SMTP id PygvCgB37E96H7Jq1OMEAw--.34383S2; Tue, 22 Sep 2026 14:26:05 +0800 (CST) From: Wang Wensheng To: pmladek@suse.com, rostedt@goodmis.org, john.ogness@linutronix.de, senozhatsky@chromium.org, linux-kernel@vger.kernel.org Cc: wsw9603@163.com Subject: [PATCH] printk_ringbuffer: Avoid needless read of prb_desc Date: Tue, 22 Sep 2026 14:25:20 +0800 Message-ID: <20260922062520.248439-1-wsw9603@163.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: PygvCgB37E96H7Jq1OMEAw--.34383S2 X-Coremail-Antispam: 1Uf129KBjvJXoW7ur1Utw15Jr17JFW7CF15Jwb_yoW5Jr4rpr s3Ka9rKr4kZ34rXr17uFy8ZF9xu3Z7A3yrWa4DZ3ySvF1xtr4Fq3ZFvryFyr15GrWDAr9I y3s0939rAa1jvF7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0pirOzxUUUUU= X-CM-SenderInfo: pzvzmliqt6il2tof0z/xtbC3h0uNmqyH314CgAA3T Content-Type: text/plain; charset="utf-8" Since commit f244b4dc53e5 ("printk: ringbuffer: Improve prb_next_seq() performance"), desc_read() allows @desc_out to be NULL. We can drop the local `desc` variable in desc_reopen_last() and prb_first_seq(). Also update the comment for desc_read(). Signed-off-by: Wang Wensheng Reviewed-by: John Ogness Reviewed-by: Petr Mladek --- kernel/printk/printk_ringbuffer.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringb= uffer.c index 85c0c854b3ce..607666d37455 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -443,8 +443,8 @@ static enum desc_state get_desc_state(unsigned long id, * descriptor is in an inconsistent state (miss or reserved), the caller c= an * only expect the descriptor's @state_var field to be valid. * - * The sequence number and caller_id can be optionally retrieved. Like all - * non-state_var data, they are only valid if the descriptor is in a + * The sequence number, caller_id, and desc can be optionally retrieved. L= ike + * all non-state_var data, they are only valid if the descriptor is in a * consistent state. */ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, @@ -1335,7 +1335,6 @@ static struct prb_desc *desc_reopen_last(struct prb_d= esc_ring *desc_ring, { unsigned long prev_state_val; enum desc_state d_state; - struct prb_desc desc; struct prb_desc *d; unsigned long id; u32 cid; @@ -1346,7 +1345,7 @@ static struct prb_desc *desc_reopen_last(struct prb_d= esc_ring *desc_ring, * To reduce unnecessarily reopening, first check if the descriptor * state and caller ID are correct. */ - d_state =3D desc_read(desc_ring, id, &desc, NULL, &cid); + d_state =3D desc_read(desc_ring, id, NULL, NULL, &cid); if (d_state !=3D desc_committed || cid !=3D caller_id) return NULL; =20 @@ -2007,14 +2006,13 @@ u64 prb_first_seq(struct printk_ringbuffer *rb) { struct prb_desc_ring *desc_ring =3D &rb->desc_ring; enum desc_state d_state; - struct prb_desc desc; unsigned long id; u64 seq; =20 for (;;) { id =3D atomic_long_read(&rb->desc_ring.tail_id); /* LMM(prb_first_seq:A)= */ =20 - d_state =3D desc_read(desc_ring, id, &desc, &seq, NULL); /* LMM(prb_firs= t_seq:B) */ + d_state =3D desc_read(desc_ring, id, NULL, &seq, NULL); /* LMM(prb_first= _seq:B) */ =20 /* * This loop will not be infinite because the tail is --=20 2.43.0