From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 5174E2D12F3 for ; Thu, 21 May 2026 13:47:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779371225; cv=none; b=Osru0pNbQJTHit5o4Hdwa96wq+3n5gXMEYW+O7gescc8S7ErvrZqjvN9pJ+oFm1HZNEyTEoQ694NQYfbHLhheEu5OtIs4nx+yBftCYE4jK5QEH5h/NGcIuJQ4zu01W29si2PY7pWO1Lynx8xRI+0NFjgynt24ySerHvPeQLEmLU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779371225; c=relaxed/simple; bh=HipBzwZbSzE7ksr//g8ykugyaefNuo+SYSzJKfHdl2Y=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=PKXFS7EiCLVudja6sl0QCbGBFkr7B4BT4iWEk68ieHS868nLNkhCFCT9rINc0+vZZ3xJC5KsXVmO32dn9q5Y+a+SsMWidLyHibOSxTA5kNq1nOPa4UdDZkutaCvh3xTXHdCNZd5Yr0VJcdhmKSQNiBlQpDJt5N4p+B7l+jOM3/M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UvXHar1k; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UvXHar1k" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 24F9C1F00A3F; Thu, 21 May 2026 13:47:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779371224; bh=AtgZUkr0l5IwFjKUqHKTZ0sBSZvBMwOZ6pEXD1xGKMA=; h=Date:From:To:Cc:Subject:References; b=UvXHar1kjfAh1aQ+C2HnZn9Z76xWqqbACuB7mSpXX94JOU89gGof+Y9enThk5JUlN zIyK6jhLTtoQvG1evsPKgeJJM730vxlDm+avQ0UUWgWrHsYul3pIJ4ZvhYKR0l3AmS 2A2VtfkNGL4dlP7dA0eLE6aJr92WYxVkZtd4cT9mOhTEFhubPzNtP3Vj0Y3CWhMTeo 6BrNfSTd07tbX/Od1hJch2HOXKiPOg/qeiymOJjmvjrCesWcGQ6k/wrRUDebEDhhRP ubBuPttOiJsTaUutXksgc9SYSoSrtvV9m+MZTUutCOxiRsUJu5yGx4hLKB3O7/avm1 UwJqMaWeFJrwA== Received: from rostedt by gandalf with local (Exim 4.99.2) (envelope-from ) id 1wQ3kD-00000005MRT-1uyu; Thu, 21 May 2026 09:47:25 -0400 Message-ID: <20260521134725.311592796@kernel.org> User-Agent: quilt/0.69 Date: Thu, 21 May 2026 09:47:13 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Vincent Donnefort , David Carlier Subject: [for-linus][PATCH 3/5] tracing: Fix nr_subbufs initialization in simple_ring_buffer_init_mm() References: <20260521134710.628917428@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 From: David Carlier nr_subbufs in the ring buffer metadata is always initialized to zero because it is assigned from cpu_buffer->nr_pages before the page initialization loop has run. While nr_subbufs is not currently read by the kernel, it should reflect the actual buffer geometry in the meta page for correctness. Move the assignment after the page loop so that cpu_buffer->nr_pages holds the final count. Link: https://patch.msgid.link/20260512135420.99194-1-devnexen@gmail.com Fixes: 34e5b958bdad ("tracing: Introduce simple_ring_buffer") Reviewed-by: Vincent Donnefort Assisted-by: Claude:claude-opus-4-7 Signed-off-by: David Carlier Signed-off-by: Steven Rostedt --- kernel/trace/simple_ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_buffer.c index 02af2297ae5a..f731f14d0ff7 100644 --- a/kernel/trace/simple_ring_buffer.c +++ b/kernel/trace/simple_ring_buffer.c @@ -395,7 +395,6 @@ int simple_ring_buffer_init_mm(struct simple_rb_per_cpu *cpu_buffer, memset(cpu_buffer->meta, 0, sizeof(*cpu_buffer->meta)); cpu_buffer->meta->meta_page_size = PAGE_SIZE; - cpu_buffer->meta->nr_subbufs = cpu_buffer->nr_pages; /* The reader page is not part of the ring initially */ page = load_page(desc->page_va[0]); @@ -437,6 +436,7 @@ int simple_ring_buffer_init_mm(struct simple_rb_per_cpu *cpu_buffer, return ret; } + cpu_buffer->meta->nr_subbufs = cpu_buffer->nr_pages; /* Close the ring */ bpage->link.next = &cpu_buffer->tail_page->link; cpu_buffer->tail_page->link.prev = &bpage->link; -- 2.53.0