From nobody Fri Dec 19 17:42:04 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CDF0F14291E; Sun, 24 Mar 2024 22:37:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711319859; cv=none; b=fYEZr+/BgXux6t9CpGyXNdyQJgGWw2visRYiugLrctVBysHqOn+AlWeg7pa5R0MtwtEWpYLAu/AoKeR1k3qiG7TA33rJ9B8W4Vy4HZo7UxmtbXF7xM4MEdoQWzNlPs/bVB0vmlRP7/oNXG49PiEFtPHI+ZDfEN+T/yI/CJagZDs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711319859; c=relaxed/simple; bh=55Nb6Gl3zSs4ji63PyDfoyTChWWBkNx9WldkUmv7yW4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=F7xVmEKaaUkP1JVfCBgrGRmC00lvhR0uChXPYbHfhUOpY3piWv+nz04FGuhHJEBsqeIodk5K7OZ1wvFgNbFp4BwBi64PSDea9Z3LmCyQnqP7GDYgqRPmoRA8CJyEeEFA3pdGJR1MvxdOJRscUh0wsNlybyPBdyMzXeI6vssGA54= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BUBADQqw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BUBADQqw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CE80AC433C7; Sun, 24 Mar 2024 22:37:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711319859; bh=55Nb6Gl3zSs4ji63PyDfoyTChWWBkNx9WldkUmv7yW4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BUBADQqwRLKG+vXVYhERb1zum9zrX9TybyH5boR+RRfIq+tLMwBny/bzmjGK6lm3Y V+vfh035uVcG753ETbTySi7zrVyPtzewpTvS7t6ZBK0edzIdG6DQM3RVDNvSo8GZwP i/hY6nvFSQ7PPL7eOOLNEJXWUkim7pCt1Mw6hbgEUMEBO+sq01jHWZ3VPuRJkqKF66 a6eLXrlTWx65c66yz20zHX/xD4WpISkPitw8miLdI3SEuH8iM8JuQWik48TsPIa5PU T99dLola3GB+NymK2FP3N7jMVbDeZ87Vr+9o4bA8xhW1lrfQPnLuJ+WNQO4KEJMlNi S07FV2ypsB8yw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: John Ogness , Petr Mladek , Sasha Levin Subject: [PATCH 6.8 163/715] printk: ringbuffer: Cleanup reader terminology Date: Sun, 24 Mar 2024 18:25:42 -0400 Message-ID: <20240324223455.1342824-164-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324223455.1342824-1-sashal@kernel.org> References: <20240324223455.1342824-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: John Ogness [ Upstream commit 584528d621459d1a5c31da7a591218ad3bb96d6c ] With the lockless ringbuffer, it is allowed that multiple CPUs/contexts write simultaneously into the buffer. This creates an ambiguity as some writers will finalize sooner. The documentation for the prb_read functions is not clear as it refers to "not yet written" and "no data available". Clarify the return values and language to be in terms of the reader: records available for reading. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20240207134103.1357162-9-john.ogness@linutr= onix.de Signed-off-by: Petr Mladek Stable-dep-of: b1c4c67a5e90 ("printk: ringbuffer: Skip non-finalized record= s in panic") Signed-off-by: Sasha Levin --- kernel/printk/printk_ringbuffer.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringb= uffer.c index d152b6bd35c9a..97ec25d227976 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -2080,11 +2080,13 @@ u64 prb_next_reserve_seq(struct printk_ringbuffer *= rb) } =20 /* - * Non-blocking read of a record. Updates @seq to the last finalized record - * (which may have no data available). + * Non-blocking read of a record. * - * See the description of prb_read_valid() and prb_read_valid_info() - * for details. + * On success @seq is updated to the record that was read and (if provided) + * @r and @line_count will contain the read/calculated data. + * + * On failure @seq is updated to a record that is not yet available to the + * reader, but it will be the next record available to the reader. */ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, struct printk_record *r, unsigned int *line_count) @@ -2103,7 +2105,7 @@ static bool _prb_read_valid(struct printk_ringbuffer = *rb, u64 *seq, *seq =3D tail_seq; =20 } else if (err =3D=3D -ENOENT) { - /* Record exists, but no data available. Skip. */ + /* Record exists, but the data was lost. Skip. */ (*seq)++; =20 } else { @@ -2136,7 +2138,7 @@ static bool _prb_read_valid(struct printk_ringbuffer = *rb, u64 *seq, * On success, the reader must check r->info.seq to see which record was * actually read. This allows the reader to detect dropped records. * - * Failure means @seq refers to a not yet written record. + * Failure means @seq refers to a record not yet available to the reader. */ bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq, struct printk_record *r) @@ -2166,7 +2168,7 @@ bool prb_read_valid(struct printk_ringbuffer *rb, u64= seq, * On success, the reader must check info->seq to see which record meta da= ta * was actually read. This allows the reader to detect dropped records. * - * Failure means @seq refers to a not yet written record. + * Failure means @seq refers to a record not yet available to the reader. */ bool prb_read_valid_info(struct printk_ringbuffer *rb, u64 seq, struct printk_info *info, unsigned int *line_count) --=20 2.43.0