From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Neukum Subject: Re: [PATCH v3 2/6] PM / Runtime: introduce pm_runtime_set[get]_memalloc_noio() Date: Tue, 30 Oct 2012 17:30:13 +0100 Message-ID: <2504263.kbM6W9JoH9@linux-lqwf.site> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: Alan Stern , linux-kernel@vger.kernel.org, Minchan Kim , Greg Kroah-Hartman , "Rafael J. Wysocki" , Jens Axboe , "David S. Miller" , Andrew Morton , netdev@vger.kernel.org, linux-usb@vger.kernel.org, linux-pm@vger.kernel.org, linux-mm@kvack.org To: Ming Lei Return-path: In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wednesday 31 October 2012 00:00:56 Ming Lei wrote: > On Tue, Oct 30, 2012 at 11:38 PM, Alan Stern wrote: > > > > > Okay, I see your point. But acquiring the lock here doesn't solve the > > problem. Suppose a thread is about to reset a USB mass-storage device. > > It acquires the lock and sees that the noio flag is clear. But before > > it can issue the reset, another thread sets the noio flag. > > If the USB mass-storage device is being reseted, the flag should be set > already generally. If the flag is still unset, that means the disk/network > device isn't added into system(or removed just now), so memory allocation > with block I/O should be allowed during the reset. Looks it isn't one problem, > isn't it? I am afraid it is, because a disk may just have been probed as the deviceis being reset. Regards Oliver