From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [linux-pm] [RFC][PATCH -mm 1/5] PM: Make freeze_processes SMP-safe Date: Sun, 3 Dec 2006 12:17:46 +0100 Message-ID: <200612031217.47361.rjw@sisk.pl> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: suspend-devel-bounces@lists.sourceforge.net Errors-To: suspend-devel-bounces@lists.sourceforge.net To: suspend-devel@lists.sourceforge.net Cc: pm list , Alan Stern , Pavel Machek List-Id: linux-pm@vger.kernel.org On Saturday, 2 December 2006 16:39, Alan Stern wrote: > On Sat, 2 Dec 2006, Pavel Machek wrote: > > > Hi! > > > > > > We send fake signals to them, so they enter get_signal_to_deliver() and they > > > > call try_to_freeze() from there. > > > > > > Well then, see, you're doing exactly what you said should never happen -- > > > you are freezing a user thread while it might be holding a lock that the > > > unfreezable usb-storage thread needs. > > > > > > I do not think it is okay to call get_signal_to_deliver with *any* > > lock held... Or do you have example when that is broken? > > Is get_signal_to_deliver() ever called at any time other than when the CPU > is about to switch back into user mode? No, I don't think so. There's a check in do_signal() that only allows it to call get_signal_to_deliver() in user mode. > If not then there shouldn't be any problem. The routines I was talking > about earlier hold the USB device locks while running in kernel mode, but > they release them before returning to user mode. Then everything is correct, I think. Greetings, Rafael -- You never change things by fighting the existing reality. R. Buckminster Fuller ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV