From nobody Sun Dec 28 00:48:24 2025 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 4572B6E2DB for ; Thu, 14 Dec 2023 21:42:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="rYKzl1gL"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="E4nJ9zge" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1702590128; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=w+Rj9ow8fovhfkl47C5quy90KNsRy8XmYEJxuaPSPxc=; b=rYKzl1gLfyiH9IJP+TFLliwyltsoWallmmQO2rIWW8Z/fGewTSWXqFjmYrmYTF+CeN4zKV wPontEoTCZuXFuB3Ybr6bj8SPuuXyeVscircT/Ol/ro4/4dtG60znLbdixzbjBmpbJlFq3 J3TKHO8N6BO1RKK25l+KflE1Xq/GC2yT5PjTw3ZWCPgmMuFfXHba9D9gMifVHVXsifgcar /6IPOTBBy9xorvPK9ZfRGwCxypgXJ6rrybFNb9io6crG3P4hKA5Ph1junGYvzLOycp+ckA d1JYd/lzSbUDSdRQ2G9pcAEg7G9bpuDMUoSFxsEw+Kaq+kojiFKqWrbCnXIIhg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1702590128; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=w+Rj9ow8fovhfkl47C5quy90KNsRy8XmYEJxuaPSPxc=; b=E4nJ9zgeLAGTpX7uf+GwQSKNUOUmHjHZFCXuM4dmVdN4NYPZT8iNldWycwr5Ytv/BL7qeg JD1ZUoqpcg9ry0DQ== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH printk v3 11/14] printk: ringbuffer: Consider committed as finalized in panic Date: Thu, 14 Dec 2023 22:47:58 +0106 Message-Id: <20231214214201.499426-12-john.ogness@linutronix.de> In-Reply-To: <20231214214201.499426-1-john.ogness@linutronix.de> References: <20231214214201.499426-1-john.ogness@linutronix.de> 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 Content-Type: text/plain; charset="utf-8" A descriptor in the committed state means the record does not yet exist for the reader. However, for the panic CPU, committed records should be handled as finalized records since they contain message data in a consistent state and may contain additional hints as to the cause of the panic. Add an exception for records in the commit state to not be considered non-existing when reading from the panic CPU. Signed-off-by: John Ogness --- kernel/printk/printk_ringbuffer.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringb= uffer.c index d6ed33683b8b..e7b808b829a0 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -1857,6 +1857,8 @@ static bool copy_data(struct prb_data_ring *data_ring, * descriptor. However, it also verifies that the record is finalized and = has * the sequence number @seq. On success, 0 is returned. * + * For the panic CPU, committed descriptors are also considered finalized. + * * Error return values: * -EINVAL: A finalized record with sequence number @seq does not exist. * -ENOENT: A finalized record with sequence number @seq exists, but its d= ata @@ -1875,16 +1877,25 @@ static int desc_read_finalized_seq(struct prb_desc_= ring *desc_ring, =20 /* * An unexpected @id (desc_miss) or @seq mismatch means the record - * does not exist. A descriptor in the reserved or committed state - * means the record does not yet exist for the reader. + * does not exist. A descriptor in the reserved state means the + * record does not yet exist for the reader. */ if (d_state =3D=3D desc_miss || d_state =3D=3D desc_reserved || - d_state =3D=3D desc_committed || s !=3D seq) { return -EINVAL; } =20 + /* + * A descriptor in the committed state means the record does not yet + * exist for the reader. However, for the panic CPU, committed + * records are also handled as finalized records since they contain + * message data in a consistent state and may contain additional + * hints as to the cause of the panic. + */ + if (d_state =3D=3D desc_committed && !this_cpu_in_panic()) + return -EINVAL; + /* * A descriptor in the reusable state may no longer have its data * available; report it as existing but with lost data. Or the record --=20 2.39.2