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 2E4D3C8C8; Mon, 11 Dec 2023 18:32:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="zAgEi0LT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A5C62C433C9; Mon, 11 Dec 2023 18:32:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1702319566; bh=IcV79FFZhaCReYOxcdLsEcHNYBqgi5CWhmxGns/OiuM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zAgEi0LTcoFP90oesXYtk6fpmswyizcw8KLo+BCdLB+ttGpm+sOJAQanEzpzPwvNM +qlwiUVSB1RD6UzVYy3w/+Lxe4Wt3sL4lpT/svENuda90XJmrZdP2sk1Hq5UyLHpd7 zwuNcHRS3jhQrtHNDEf4ITBIIw/d7aWfPBCs096M= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , "Steven Rostedt (Google)" Subject: [PATCH 6.6 153/244] tracing: Always update snapshot buffer size Date: Mon, 11 Dec 2023 19:20:46 +0100 Message-ID: <20231211182052.686830181@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231211182045.784881756@linuxfoundation.org> References: <20231211182045.784881756@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Steven Rostedt (Google) commit 7be76461f302ec05cbd62b90b2a05c64299ca01f upstream. It use to be that only the top level instance had a snapshot buffer (for latency tracers like wakeup and irqsoff). The update of the ring buffer size would check if the instance was the top level and if so, it would also update the snapshot buffer as it needs to be the same as the main buffer. Now that lower level instances also has a snapshot buffer, they too need to update their snapshot buffer sizes when the main buffer is changed, otherwise the following can be triggered: # cd /sys/kernel/tracing # echo 1500 > buffer_size_kb # mkdir instances/foo # echo irqsoff > instances/foo/current_tracer # echo 1000 > instances/foo/buffer_size_kb Produces: WARNING: CPU: 2 PID: 856 at kernel/trace/trace.c:1938 update_max_tr_single.part.0+0x27d/0x320 Which is: ret = ring_buffer_swap_cpu(tr->max_buffer.buffer, tr->array_buffer.buffer, cpu); if (ret == -EBUSY) { [..] } WARN_ON_ONCE(ret && ret != -EAGAIN && ret != -EBUSY); <== here That's because ring_buffer_swap_cpu() has: int ret = -EINVAL; [..] /* At least make sure the two buffers are somewhat the same */ if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages) goto out; [..] out: return ret; } Instead, update all instances' snapshot buffer sizes when their main buffer size is updated. Link: https://lkml.kernel.org/r/20231205220010.454662151@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Fixes: 6d9b3fa5e7f6 ("tracing: Move tracing_max_latency into trace_array") Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6399,8 +6399,7 @@ static int __tracing_resize_ring_buffer( return ret; #ifdef CONFIG_TRACER_MAX_TRACE - if (!(tr->flags & TRACE_ARRAY_FL_GLOBAL) || - !tr->current_trace->use_max_tr) + if (!tr->current_trace->use_max_tr) goto out; ret = ring_buffer_resize(tr->max_buffer.buffer, size, cpu);