From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756416Ab0J0UG7 (ORCPT ); Wed, 27 Oct 2010 16:06:59 -0400 Received: from nm10-vm0.bullet.mail.ac4.yahoo.com ([98.139.53.194]:31939 "HELO nm10-vm0.bullet.mail.ac4.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751889Ab0J0UG4 (ORCPT ); Wed, 27 Oct 2010 16:06:56 -0400 X-Yahoo-Newman-Id: 127165.22043.bm@omp1034.mail.ac4.yahoo.com X-Yahoo-SMTP: fzDSGlOswBCWnIOrNw7KwwK1j9PqyNbe5PtLKiS4dDU.UNl_t6bdEZu9tTLW X-YMail-OSG: Dr6JiVoVM1nTzHglNwwds7doU5auDLThwGIRb5rIT7KeqOf vhhUTqkIcHyj9N3GIwEbiu0F4vMC8NkP8woySt5LS38UE56y9MrhHWJQTJZJ EovGslZDm.ac70tl9mg2DUWkL5GREvdxQxv4Kx_zqnnsx5WnrScnUe6epSIh .Rmn8jPwhQorJiVOb8dHR5a5iiYmJyLArJeFdgwagSfP4I9ZlTM8qOAvC9z8 gAd99cTgh8N1AV0mP7wNwIZ7Zup3SnjHDaoMxSAfcr2qu66Ev.IBzkbU5kD_ jKCD1pMQ71USv6cQfAU_5_uupOtLJxApJHPZ9QZq_AgWNwyPrgjT5vhjOPWm 8u5AABX72U3lR63AkdSvxNnnQm042D8qe5GkDaqtaAqMkZ2Eimsuf_uVjJ0C WQ1NXJI27Y_o2NpGQLQMcL7C3oPeD7BProuYYnTs11uf8apI5pna6I2rjjc0 sp_q1Jzl5FzIsb_O54YwcRx_klg-- X-Yahoo-Newman-Property: ymail-3 Subject: Re: [ANNOUNCE] Status of unlocked_qcmds=1 operation for .37 From: "Nicholas A. Bellinger" To: Mike Anderson Cc: James Bottomley , Andi Kleen , linux-kernel , linux-scsi , Vasu Dev , Tim Chen , Matthew Wilcox , Mike Christie , Jens Axboe , James Smart , Andrew Vasquez , FUJITA Tomonori , Hannes Reinecke , Joe Eykholt , Christoph Hellwig , Jon Hawley , Brian King , Christof Schmitt , Tejun Heo , Andrew Morton , "H. Peter Anvin" In-Reply-To: <20101027192025.GA1349@linux.vnet.ibm.com> References: <1288130914.5169.97.camel@haakon2.linux-iscsi.org> <1288132071.8283.689.camel@mulgrave.site> <1288132464.5169.112.camel@haakon2.linux-iscsi.org> <1288133450.8283.723.camel@mulgrave.site> <1288134048.5169.132.camel@haakon2.linux-iscsi.org> <1288134713.19649.11.camel@mulgrave.site> <1288135918.5169.149.camel@haakon2.linux-iscsi.org> <20101027075349.GA32585@gargoyle.fritz.box> <1288189658.4692.13.camel@mulgrave.site> <1288202802.5169.202.camel@haakon2.linux-iscsi.org> <20101027192025.GA1349@linux.vnet.ibm.com> Content-Type: text/plain Date: Wed, 27 Oct 2010 12:55:18 -0700 Message-Id: <1288209318.5169.213.camel@haakon2.linux-iscsi.org> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2010-10-27 at 12:20 -0700, Mike Anderson wrote: > Nicholas A. Bellinger wrote: > > On Wed, 2010-10-27 at 09:27 -0500, James Bottomley wrote: > > > On Wed, 2010-10-27 at 09:53 +0200, Andi Kleen wrote: > > > > > This sounds like a pretty reasonable compromise that I think is slightly > > > > > less risky for the LLDs with the ghosts and cob-webs hanging off of > > > > > them. > > > > > > > > They won't get tested either next release cycle. Essentially > > > > near nobody uses them. > > > > > > > > > > > > > > What do you think..? > > > > > > > > Standard linux practice is to simply push the locks down. That's a pretty > > > > mechanical operation and shouldn't be too risky > > > > > > > > With some luck you could even do it with coccinelle. > > > > > > Precisely ... if we can do the push down now as a mechanical > > > transformation we can put it in the current merge window as a low risk > > > API change. > > > > I disagree that touching every single legacy LLD's SHT->queuecommand() > > and failure paths in that code is a low rist change. > > > > > This gives us optimal exposure to the rc sequence to sort > > > out any problems that arise (or drivers that got missed) with the lowest > > > risk of such problems actually arising. > > > > Yes, > > > > > Given the corner cases and the > > > late arrival of fixes, the serial number changes are just too risky for > > > the current merge window. > > > > I think with andmike's testing and ACKs for the necessary scsi_error.c > > changes this would be an acceptable risk. > > > > Adding SCSI_EH_SOFTIRQ_DONE in scsi_softirq_done is not going to provide > value in scsi_try_to_abort_cmd. scsi_softirq_done calls scsi_eh_scmd_add > without the SCSI_EH_CANCEL_CMD flag set which will stop > scsi_try_to_abort_cmd from being called. > > Removing the serial_number check in scsi_try_to_abort_cmd and not > replacing it may be the correct action as we should be relying on the > block complete checking. That said what James has indicated about > splitting the serial number change out seems like the lower risk approach > at this time. > Hmm, that is unfortuate.. So in this case it would make sense to drop the explict LLD usage of scsi_cmd_get_serial(), and re-include this into scsi_dispatch_cmd() for all LLDs and have to deal with a per scsi_host atomic_t serial_number counter. Anyways, I will go ahead an respin another series to follow this logic shortly. The other question that was mentioned in my email yesterday would be if the clearing of a non atomic_t cmd->serial_number from scsi_softirq_done() -> scsi_try_to_abort_cmd() is safe to begin with..? Does this need to be converted to an atomic_t as well to present a subtle race outside of any of the host_lock-less series of patches..? --nab