From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755185AbcEBU4n (ORCPT ); Mon, 2 May 2016 16:56:43 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:54846 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753488AbcEBU4g (ORCPT ); Mon, 2 May 2016 16:56:36 -0400 Date: Mon, 2 May 2016 13:56:34 -0700 From: Andrew Morton To: Oleksandr Natalenko Cc: Ben Hutchings , Lee Jones , Wolfram Sang , Roger Tseng , linux-kernel@vger.kernel.org, Oleg Nesterov Subject: Re: [PATCH RESEND] rtsx_usb_ms: Use msleep_interruptible() in polling loop Message-Id: <20160502135634.ccbfb7f58798b7a217319b98@linux-foundation.org> In-Reply-To: <7afcd6e57d09772699ac37b59db98617@natalenko.name> References: <7afcd6e57d09772699ac37b59db98617@natalenko.name> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 02 May 2016 23:17:41 +0300 Oleksandr Natalenko wrote: > This patch has already been posted to LKML by Ben Hutchings ~6 months > ago, but AFAIK no further action were performed. However, this patch > really fixes weird loadavg with RTS5129 card reader, so I would wonder > if this could be merged. AFAIK, it has been applied to some distros' > kernels, e.g., Ubuntu. > > Original Ben's message goes below. > > rtsx_usb_ms creates a task that mostly sleeps, but tasks in > uninterruptible sleep still contribute to the load average (for > bug-compatibility with Unix). A load average of ~1 on a system that > should be idle is somewhat alarming. > > Change the sleep to be interruptible, but still ignore signals. > > A better fix might be to replace this loop with a delayed work item. > hm. > index 1105db2..645dede 100644 > --- a/drivers/memstick/host/rtsx_usb_ms.c > +++ b/drivers/memstick/host/rtsx_usb_ms.c > @@ -706,7 +706,8 @@ poll_again: > if (host->eject) > break; > > - msleep(1000); > + if (msleep_interruptible(1000)) > + flush_signals(current); > } > > complete(&host->detect_ms_exit); flush_signals() is a bit scary. If this was a userspace task and it had (say) SIGINT pending then it would be very rude for a device driver to rub that out. But this isn't a userspace task - it's a kthread. So I don't *think* it can get any signals anyway? And looking at Oleg's 9e7c8f8c62c1e1cda203b it appears that flush_signals() is for flushing signals of a userspace task, not a kthread? Despite the comment "Flush all pending signals for this kthread". Confused. It's been a while since I looked at this stuff and people have mucked with it. Oleg, can you please sort me out?