Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753543Ab2EXIFr (ORCPT ); Thu, 24 May 2012 04:05:47 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:53356 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750808Ab2EXIFm (ORCPT ); Thu, 24 May 2012 04:05:42 -0400 Message-ID: <1337846737.2955.11.camel@dabdike.int.hansenpartnership.com> Subject: Re: 3.4.0-02580-g72c04af regression on sparc64 - partitions not recognized From: James Bottomley To: Dan Williams Cc: David Miller , mroos@linux.ee, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, stern@rowland.harvard.edu, "Rafael J. Wysocki" , Arjan van de Ven Date: Thu, 24 May 2012 09:05:37 +0100 In-Reply-To: References: <20120522.151217.278388169416093561.davem@davemloft.net> <20120523.140451.386112705611304887.davem@davemloft.net> <1337813770.3013.37.camel@dabdike.int.hansenpartnership.com> <1337826142.6877.7.camel@dwillia2-mobl> <1337845361.2955.6.camel@dabdike.int.hansenpartnership.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6337 Lines: 151 On Thu, 2012-05-24 at 00:54 -0700, Dan Williams wrote: > On Thu, May 24, 2012 at 12:42 AM, James Bottomley > wrote: > > On Wed, 2012-05-23 at 19:22 -0700, Dan Williams wrote: > >> On Wed, 2012-05-23 at 23:56 +0100, James Bottomley wrote: > >> > On Wed, 2012-05-23 at 14:04 -0400, David Miller wrote: > >> > > From: Meelis Roos > >> > > Date: Wed, 23 May 2012 19:46:46 +0300 (EEST) > >> > > > >> > > CC:'ing interested parties. > >> > > > >> > > >> > Just tested 3.4.0-02580-g72c04af on about 10 machines. While most of > >> > > >> > them work (including 3 different sparc64 machines with real scsi disks), > >> > > >> > Sun Netra X1 with pata_ali and IDE disk consistently fails to boot. sda > >> > > >> > is recognized but no partitions. 3.3.0 works fine, as did something > >> > > >> > around 3.4-rc7 (plain 3.4 not tested yet). No other IDE machines tested > >> > > >> > yet since I have none with remote console at the moment. > >> > > >> > >> > > >> If 3.4.0-final is OK, start bisecting from v3.4.0 until 72c04af. One > >> > > >> possibility could be the sparc64 NOBOOTMEM conversion that went into > >> > > >> the merge window. > >> > > > > >> > > > Bisecting leads to this commit: > >> > > > > >> > > > a7a20d103994fd760766e6c9d494daa569cbfe06 is the first bad commit > >> > > > commit a7a20d103994fd760766e6c9d494daa569cbfe06 > >> > > > Author: Dan Williams > >> > > > Date: Thu Mar 22 17:05:11 2012 -0700 > >> > > > > >> > > > [SCSI] sd: limit the scope of the async probe domain > >> > > >> > My theory is that this is an init problem: The assumption in a lot of > >> > our code is that async_synchronize_full() waits for everything ... even > >> > the domain specific async schedules, which isn't true. > >> > > >> > The code in init that makes this assumption is wait_for_device_probe(). > >> > There's also a fun async_synchronize_full() in init_post() that assumes > >> > it can free the init memory after, which would fail badly if anything in > >> > init used an async domain. > >> > > >> > So either we fix the assumptions or we can't use domain specific async > >> > schedules. > >> > > >> > >> Hm, we already have cases of code not trusting the semantics of > >> wait_for_device_probe(), especially as it relates to async scanning like > >> in kernel/power/hibernate.c: > >> > >> /* > >> * Some device discovery might still be in progress; we need > >> * to wait for this to finish. > >> */ > >> wait_for_device_probe(); > >> > >> if (resume_wait) { > >> while ((swsusp_resume_device = name_to_dev_t(resume_file)) == 0) > >> msleep(10); > >> async_synchronize_full(); > >> } > >> > >> /* > >> * We can't depend on SCSI devices being available after loading > >> * one of their modules until scsi_complete_async_scans() is > >> * called and the resume device usually is a SCSI one. > >> */ > >> scsi_complete_async_scans(); > > > > This is actually looks wrong: it works if SCSI is built in, but it's a > > nop if SCSI is a module (the nop function is gated by the else clause of > > #ifdef CONFIG_SCSI) > > > > Rafael, you added this not via the SCSI tree, is that the intention? > > > >> ...so it seems scsi_complete_async_scans() should take care to flush sd > >> probe actions as well... here is a test patch: > >> > >> --- snip --- > >> > >> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c > >> index 8906557..05a92d3 100644 > >> --- a/drivers/scsi/scsi_scan.c > >> +++ b/drivers/scsi/scsi_scan.c > >> @@ -141,13 +141,13 @@ struct async_scan_data { > >> * started scanning after this function was called may or may not have > >> * finished. > >> */ > >> -int scsi_complete_async_scans(void) > >> +static void __scsi_complete_async_scans(void) > >> { > >> struct async_scan_data *data; > >> > >> do { > >> if (list_empty(&scanning_hosts)) > >> - return 0; > >> + return; > >> /* If we can't get memory immediately, that's OK. Just > >> * sleep a little. Even if we never get memory, the async > >> * scans will finish eventually. > >> @@ -181,6 +181,13 @@ int scsi_complete_async_scans(void) > >> spin_unlock(&async_scan_lock); > >> > >> kfree(data); > >> +} > >> + > >> +int scsi_complete_async_scans(void) > >> +{ > >> + __scsi_complete_async_scans(); > >> + async_synchronize_full_domain(&scsi_sd_probe_domain); > >> + > >> return 0; > >> } > > > > But this still doesn't fix the boot problem, does it? ... unless we want > > to add a scsi_complete_async_scans() into init/do_mounts.c, which looks > > like piling one hack on top of another. > > I managed to convince myself that one in prepare_namespace() was > probably not needed because of the late_initcall of > scsi_complete_async_scans() in the built-in case and in the module > case the initramfs should be taking care of it. Ah, now I remember, that was the hack we put in to prevent a boot panic caused by a similar thing ... mainly because async SCSI scanning uses a custom infrastructure. > > I really think the correct fix is to have wait_for_device_probe() > > actually wait until all probes have completed and everything is > > discovered, that way we get the semantics the name implies and boot > > should just work. > > > > ...but wouldn't it need to go something like: > > wait_for_device_probe(); /* all pci drivers probed */ > scsi_complete_async_scans(): /* flush host scans */ > wait_for_device_probe(); /* all recently attached sd devices probed */ > > ? No .. the point is if we wait for all outstanding scans instead of just those in the async_running domain, it will "just work", with no special SCSI magic. James -- 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/