From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [PATCH] sd: use async_probe cookie to avoid deadlocks Date: Tue, 21 Mar 2017 13:42:20 +0000 Message-ID: <1490103725.2602.7.camel@sandisk.com> References: <1490098475-21884-1-git-send-email-hare@suse.de> <1490101519.2412.13.camel@HansenPartnership.com> <1490103027.2602.5.camel@sandisk.com> <1490103238.2412.17.camel@HansenPartnership.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Received: from esa5.hgst.iphmx.com ([216.71.153.144]:26359 "EHLO esa5.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756517AbdCUNme (ORCPT ); Tue, 21 Mar 2017 09:42:34 -0400 In-Reply-To: <1490103238.2412.17.camel@HansenPartnership.com> Content-Language: en-US Content-ID: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "James.Bottomley@HansenPartnership.com" , "hare@suse.de" , "martin.petersen@oracle.com" Cc: "linux-scsi@vger.kernel.org" , "hare@suse.com" On Tue, 2017-03-21 at 09:33 -0400, James Bottomley wrote: > On Tue, 2017-03-21 at 13:30 +0000, Bart Van Assche wrote: > > On Tue, 2017-03-21 at 09:05 -0400, James Bottomley wrote: > > > How does this preserve ordering? It looks like you have one cookie=20 > > > per sdkp ... is there some sort of ordering guarantee I'm not > > > seeing? > >=20 > > Hello James, > >=20 > > Since the probe order depends on the order in which __async_probe()=20 > > adds entries to the "pending" list, and since the order of the > > __async_probe() calls is not changed by this patch, shouldn't the=20 > > probe order be preserved by this patch? >=20 > I don't know: that's what I'm asking. I believe they complete in order > for a single domain. I thought ordering isn't preserved between > domains? So moving to multiple domains loses us ordering of disk > appearance. Right, since sd_remove() doesn't wait any longer for completion of probes from other domains the multi-domain probing behavior may change due to this patch. However, the multi-domain probing order was already dependent on the duration of individual probes so I don't think that it is guaranteed today that multi-domain probing happens in the same order during every boot. I hope that the change introduced by this patch will be considered acceptable= . Bart.=