From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans de Goede Subject: Re: [PATCH] uas: replace WARN_ON_ONCE() with assert_spin_locked(). Date: Mon, 11 Aug 2014 21:53:34 +0200 Message-ID: <53E91F3E.6000308@redhat.com> References: <1407743966-25325-1-git-send-email-sanjeev_sharma@mentor.com> <20140811181905.GA25727@roeck-us.net> <53E9118B.3020309@redhat.com> <20140811190823.GA18503@roeck-us.net> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:9173 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754818AbaHKTxn (ORCPT ); Mon, 11 Aug 2014 15:53:43 -0400 In-Reply-To: <20140811190823.GA18503@roeck-us.net> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Guenter Roeck Cc: Sanjeev Sharma , gregkh@linuxfoundation.org, kraxel@redhat.com, mdharm-usb@one-eyed-alien.net, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Hi, On 08/11/2014 09:08 PM, Guenter Roeck wrote: > On Mon, Aug 11, 2014 at 08:55:07PM +0200, Hans de Goede wrote: >> Hi, >> >> On 08/11/2014 08:19 PM, Guenter Roeck wrote: >>> On Mon, Aug 11, 2014 at 01:29:26PM +0530, Sanjeev Sharma wrote: >>>> spin_is_locked() always return false in uniprocessor configuration and therefore it >>>> would be advise to repalce with assert_spin_locked(). >>>> >>>> Signed-off-by: Sanjeev Sharma >>>> --- >>>> drivers/usb/storage/uas.c | 8 ++++---- >>>> 1 file changed, 4 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c >>>> index 3f42785..8e5877d 100644 >>>> --- a/drivers/usb/storage/uas.c >>>> +++ b/drivers/usb/storage/uas.c >>>> @@ -154,7 +154,7 @@ static void uas_mark_cmd_dead(struct uas_dev_info *devinfo, >>>> struct scsi_cmnd *cmnd = container_of(scp, struct scsi_cmnd, SCp); >>>> >>>> uas_log_cmd_state(cmnd, caller); >>>> - WARN_ON_ONCE(!spin_is_locked(&devinfo->lock)); >>>> + assert_spin_locked(&devinfo->lock); >>> >>> Seems to me that replacing WARN_ON_ONCE (which may be annoying but only >>> creates a traceback, and only once) with assert_spin_locked (which >>> crashes the kernel) is a bit drastic. >> >> I can see your point, but so far these paranoia checks have never triggered, >> and having them trigger _always_ one some uni-processor (which is the reason >> for this patch) to me seems the worse problem of the 2. >> > If those are just paranoia checks, it might make sense to use > lockdep_assert_held() to reduce runtime overhead if lockdep > debugging is disabled. Ah yes, that is a good idea. Sanjeev, can you please send a v2 using lockdep_assert_held() ? Thanks & Regards, Hans (the uas driver maintainer)