From mboxrd@z Thu Jan 1 00:00:00 1970 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 7407936308A; Tue, 25 Aug 2026 05:21:33 +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=1787635293; cv=none; b=NrZYWTdrHtONU5mS925BLWcuThBTsOaFirGDFQEl4e19PHiYLTcMd/mPsIzIUNKhyeX5XVtFo7vlvCVVQUdoTk/zD/VXLSE6dpsHW+D5y1emaF0IA/FgIX7Ag/QpAuK7euBXM7G5M0aKFfVeKnMblVVv8HqsUtRGiKAO/09j7Y0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787635293; c=relaxed/simple; bh=6Y1XbZWfQiu+oywBa1EwFn9wtGU0Z1a2BMaPr+MkY/U=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Oen7WB8B0NLxKvnoHCxHMPY7b2AoUS3znFwReQaIijK5YGSlFiOI/Ed+cCSCJ5dm8BA/taNzvWAZ7b/VPn+TahQ5H/p+66Fb25XL22MfHwuCKqia5rkOAZqNap4rauC9PJJsJQ7aqNFOa034+4ATkS6lfzQfTWKisPsiOtURKrU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=shmbcStw; 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="shmbcStw" Received: by smtp.kernel.org (Postfix) with ESMTPS id 464F8C2BCFB; Tue, 25 Aug 2026 05:21:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1787635293; bh=6Y1XbZWfQiu+oywBa1EwFn9wtGU0Z1a2BMaPr+MkY/U=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=shmbcStwdzlHkU1pz/DI2vV39TmrISx9lmIQrhIfUmUx/y/qLodk9wiYX96kxKGvB nobQLcSIyb7/KOr1JSD4u6K60xTmg43z+/6OgwF+4MW63MHdWfZ03l1WezOG/qiHy3 xVgWRTfMzHT2BvfEm7+/NE/AoPqxvkAimXBV1m4fxifvVV1do9PikYOBWRi84YiwgH E9eulQP0H5nywd9RMIvmN5ysSli0to8x5fmkQ7hjUDs0WmjXTxLO4b7mddN8mV/vvU tAwEzu7EagndrRIn0lJ40Rk0PNGsZJuvvzgmNuJAdkWFwbl11Eh90rYRP0Z6ETxUBE VuYprDepuR04g== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2A853C61DB6; Tue, 25 Aug 2026 05:21:33 +0000 (UTC) From: Ivan Immanuel Shaji via B4 Relay Date: Tue, 25 Aug 2026 01:20:38 -0400 Subject: [PATCH 2/2] ring-buffer: Stop remote reader update when page swap fails Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260825-kernel-patch-1-v1-2-e9349aa0b165@gmail.com> References: <20260825-kernel-patch-1-v1-0-e9349aa0b165@gmail.com> In-Reply-To: <20260825-kernel-patch-1-v1-0-e9349aa0b165@gmail.com> To: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Vincent Donnefort Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, stable@vger.kernel.org, Ivan Immanuel Shaji X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1787635292; l=1498; i=ivanimmanuel1234@gmail.com; s=20260825; h=from:subject:message-id; bh=Yt3jJEKjDX8/on3DO9yN+/vqaXIqohP/+YVJCaaE2TA=; b=KmTfJ3GvG/u3YrBfBZAyX5nOKK+yVn9H2LRQsIdURBZL6eyXNJKeUDzGR4U1N8WGLf9D7C5OU bnWoYbWgI93DAs3LZpK+WUo1uq3qAEUUgZNrxB3zqY9axeBmdR+8JnZ X-Developer-Key: i=ivanimmanuel1234@gmail.com; a=ed25519; pk=Wx8O3UUs3XneDkbqbOJJnlNdWSpEf2tWbTAoE7/vnqE= X-Endpoint-Received: by B4 Relay for ivanimmanuel1234@gmail.com/20260825 with auth_id=975 X-Original-From: Ivan Immanuel Shaji Reply-To: ivanimmanuel1234@gmail.com From: Ivan Immanuel Shaji The remote swap_reader_page callback can fail when the writer moves the head before the remote catches it. __rb_get_reader_page_from_remote() warns about that failure but continues with the unchanged reader ID and rearranges the local page list as though the swap succeeded. Stop immediately after warning. Callers already handle a NULL reader page as a failed attempt, and this avoids splicing the same page as both the previous and new reader. Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes") Cc: stable@vger.kernel.org Assisted-by: LLM sparse Signed-off-by: Ivan Immanuel Shaji --- kernel/trace/ring_buffer.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 3c3ed639923d..d11b2759caac 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -5805,8 +5805,9 @@ __rb_get_reader_page_from_remote(struct ring_buffer_per_cpu *cpu_buffer) prev_reader = cpu_buffer->subbuf_ids[cpu_buffer->meta_page->reader.id]; - WARN_ON_ONCE(cpu_buffer->remote->swap_reader_page(cpu_buffer->cpu, - cpu_buffer->remote->priv)); + if (WARN_ON_ONCE(cpu_buffer->remote->swap_reader_page(cpu_buffer->cpu, + cpu_buffer->remote->priv))) + return NULL; /* nr_pages doesn't include the reader page */ if (WARN_ON_ONCE(cpu_buffer->meta_page->reader.id > cpu_buffer->nr_pages)) return NULL; -- 2.53.0