From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:56542 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727583AbeI0PkR (ORCPT ); Thu, 27 Sep 2018 11:40:17 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jason Behmer , Vaibhav Nagarnaik , "Steven Rostedt (VMware)" Subject: [PATCH 4.14 33/64] ring-buffer: Allow for rescheduling when removing pages Date: Thu, 27 Sep 2018 11:03:50 +0200 Message-Id: <20180927090254.814422280@linuxfoundation.org> In-Reply-To: <20180927090249.801943776@linuxfoundation.org> References: <20180927090249.801943776@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vaibhav Nagarnaik commit 83f365554e47997ec68dc4eca3f5dce525cd15c3 upstream. When reducing ring buffer size, pages are removed by scheduling a work item on each CPU for the corresponding CPU ring buffer. After the pages are removed from ring buffer linked list, the pages are free()d in a tight loop. The loop does not give up CPU until all pages are removed. In a worst case behavior, when lot of pages are to be freed, it can cause system stall. After the pages are removed from the list, the free() can happen while the work is rescheduled. Call cond_resched() in the loop to prevent the system hangup. Link: http://lkml.kernel.org/r/20180907223129.71994-1-vnagarnaik@google.com Cc: stable@vger.kernel.org Fixes: 83f40318dab00 ("ring-buffer: Make removal of ring buffer pages atomic") Reported-by: Jason Behmer Signed-off-by: Vaibhav Nagarnaik Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/ring_buffer.c | 2 ++ 1 file changed, 2 insertions(+) --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1479,6 +1479,8 @@ rb_remove_pages(struct ring_buffer_per_c tmp_iter_page = first_page; do { + cond_resched(); + to_remove_page = tmp_iter_page; rb_inc_page(cpu_buffer, &tmp_iter_page);