Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932357Ab0FDPTr (ORCPT ); Fri, 4 Jun 2010 11:19:47 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:55989 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751523Ab0FDPTq (ORCPT ); Fri, 4 Jun 2010 11:19:46 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=cQOegh+1co1ZWBTiWH5BuHZjjC32b4fC2Qy4bgup4KgJkvIXLXuOT7tt9SOnzV+9Yk qLSNvehCfG98HEoBQeu9toFCYRx1qCCx028LfljM1dPiXPnpiEVDP3VoFzVynU4fsU/z hFhjHUCpJqXl3/XNxVQqcx+KT726ABZE40jqo= Subject: Re: [linux-pm] Is it supposed to be ok to call del_gendisk while userspace is frozen? From: Maxim Levitsky To: Alan Stern Cc: Pavel Machek , Jens Axboe , "Rafael J. Wysocki" , linux-pm , linux-kernel , Andrew Morton In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Date: Fri, 04 Jun 2010 18:19:38 +0300 Message-ID: <1275664778.4596.1.camel@maxim-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2230 Lines: 59 On Fri, 2010-06-04 at 10:59 -0400, Alan Stern wrote: > On Fri, 4 Jun 2010, Maxim Levitsky wrote: > > > On Thu, 2010-03-04 at 14:53 +0100, Pavel Machek wrote: > > > Hi! > > > > > > > > journalling assumptions broken: commit block is there, but previous > > > > > blocks are not intact. Data loss. > > > > > > > > > > ...and that was the first I could think about. Lets not do > > > > > this. Barriers were invented for a reason. > > > > > > > > Very well. Then we still need a solution to the original problem: > > > > Devices sometimes need to be unregistered during resume, but > > > > del_gendisk() blocks on the writeback thread, which is frozen until > > > > after the resume finishes. How do you suggest this be fixed? > > > > > > Avoid unregistering device during resume. Instead, return errors until > > > resume is done and you can call del_gendisk? > > > > This won't help ether. The same driver needs to unregister perfectly > > working device on suspend, because the user might replace the card > > during suspend and fool the os. > > There is a setting, CONFIG_MMC_UNSAFE_RESUME and I use it, but it isn't > > default. > > People have generally agreed that the best answer is to have > del_gendisk always thaw the writeback thread. Now the question is how to do that? :-) Best regards, Maxim Levitsky > > > Anyway to revive that old thread, how about introducing new > > del_gendisk_no_sync? > > > > A less safe version of del_gendisk, but which won't sync the filesystem. > > Since driver knows that card is gone, there is no point of syncing it. > > > > (the sync is done by invalidate_partition, so some flag should be > > propagated to it). > > That might work for mmc, but it wouldn't help other drivers subject to > the same problem. > > Besides, it's subject to races. What if the card _isn't_ gone, but for > some other reason the driver wants to unregister the device at a time > when the writeback thread is frozen? > > Alan Stern > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/