Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752877AbZDAExT (ORCPT ); Wed, 1 Apr 2009 00:53:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751225AbZDAExF (ORCPT ); Wed, 1 Apr 2009 00:53:05 -0400 Received: from acsinet11.oracle.com ([141.146.126.233]:36338 "EHLO acsinet11.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751195AbZDAExE (ORCPT ); Wed, 1 Apr 2009 00:53:04 -0400 Message-ID: <49D2F2D4.9090008@oracle.com> Date: Tue, 31 Mar 2009 21:51:32 -0700 From: Randy Dunlap Organization: Oracle Linux Engineering User-Agent: Thunderbird 2.0.0.6 (X11/20070801) MIME-Version: 1.0 To: Rusty Russell CC: Linux Kernel Mailing List , "Rafael J. Wysocki" , Bjorn Helgaas , andreas.herrmann3@amd.com, Andrew Morton Subject: Re: 2.6.29 boot hang References: <49D280EF.1080507@oracle.com> <200904011012.11527.rusty@rustcorp.com.au> In-Reply-To: <200904011012.11527.rusty@rustcorp.com.au> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Source-IP: acsmt701.oracle.com [141.146.40.71] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090205.49D2F2DF.013D:SCFMA4539814,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4909 Lines: 147 Rusty Russell wrote: > On Wednesday 01 April 2009 07:15:35 Randy Dunlap wrote: >> On a 4-proc x86_64 (HP BladeCenter, AMD CPUs) system, booting 2.6.29 >> (or earlier, back to 2.6.28-6921-g873392c) hangs during boot. >> >> git bisect says: >> 873392ca514f87eae39f53b6944caf85b1a047cb is first bad commit >> commit 873392ca514f87eae39f53b6944caf85b1a047cb >> Author: Rusty Russell >> Date: Wed Dec 31 23:54:56 2008 +1030 >> >> PCI: work_on_cpu: use in drivers/pci/pci-driver.c > > ... > >> If I change CONFIG_MICROCODE_AMD=y to CONFIG_MICROCODE_AMD=n & rebuild, >> the kernel boots successfully. > > How very very odd. My first thought was a deadlock with keventd used > by work_on_cpu (changed in latest Linus tree), but the microcode code at > that version doesn't use work_on_cpu. Yep, I thought it a bit odd also. > So I don't think that's it, but this patch should canonically eliminate it: > > Subject: work_on_cpu(): rewrite it to create a kernel thread on demand > From: Andrew Morton This patch doesn't apply to 2.6.29-final, but it does apply to 2.6.29-git8, so I applied/tested it there. with surprising results (at least to me). 2.6.29-git8 works for me without any patches applied. After applying this patch, I get the same boot hang that I was seeing with 2.6.29-final. Make sense to you?? Thanks for your help. > The various implemetnations and proposed implemetnations of work_on_cpu() > are vulnerable to various deadlocks because they all used queues of some > form. > > Unrelated pieces of kernel code thus gained dependencies wherein if one > work_on_cpu() caller holds a lock which some other work_on_cpu() callback > also takes, the kernel could rarely deadlock. > > Fix this by creating a short-lived kernel thread for each work_on_cpu() > invokation. > > This is not terribly fast, but the only current caller of work_on_cpu() is > pci_call_probe(). > > It would be nice to find some other way of doing the node-local > allocations in the PCI probe code so that we can zap work_on_cpu() > altogether. The code there is rather nasty. I can't think of anything > simple at this time... > > Cc: Rusty Russell > Cc: Ingo Molnar > Signed-off-by: Andrew Morton > Signed-off-by: Rusty Russell > --- > kernel/workqueue.c | 36 +++++++++++++++++++----------------- > 1 file changed, 19 insertions(+), 17 deletions(-) > > diff -puN kernel/workqueue.c~work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand kernel/workqueue.c > --- a/kernel/workqueue.c~work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand > +++ a/kernel/workqueue.c > @@ -985,20 +985,20 @@ undo: > } > > #ifdef CONFIG_SMP > -static struct workqueue_struct *work_on_cpu_wq __read_mostly; > > struct work_for_cpu { > - struct work_struct work; > + struct completion completion; > long (*fn)(void *); > void *arg; > long ret; > }; > > -static void do_work_for_cpu(struct work_struct *w) > +static int do_work_for_cpu(void *_wfc) > { > - struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work); > - > + struct work_for_cpu *wfc = _wfc; > wfc->ret = wfc->fn(wfc->arg); > + complete(&wfc->completion); > + return 0; > } > > /** > @@ -1009,17 +1009,23 @@ static void do_work_for_cpu(struct work_ > * > * This will return the value @fn returns. > * It is up to the caller to ensure that the cpu doesn't go offline. > + * The caller must not hold any locks which would prevent @fn from completing. > */ > long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) > { > - struct work_for_cpu wfc; > - > - INIT_WORK(&wfc.work, do_work_for_cpu); > - wfc.fn = fn; > - wfc.arg = arg; > - queue_work_on(cpu, work_on_cpu_wq, &wfc.work); > - flush_work(&wfc.work); > - > + struct task_struct *sub_thread; > + struct work_for_cpu wfc = { > + .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion), > + .fn = fn, > + .arg = arg, > + }; > + > + sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu"); > + if (IS_ERR(sub_thread)) > + return PTR_ERR(sub_thread); > + kthread_bind(sub_thread, cpu); > + wake_up_process(sub_thread); > + wait_for_completion(&wfc.completion); > return wfc.ret; > } > EXPORT_SYMBOL_GPL(work_on_cpu); > @@ -1035,8 +1041,4 @@ void __init init_workqueues(void) > hotcpu_notifier(workqueue_cpu_callback, 0); > keventd_wq = create_workqueue("events"); > BUG_ON(!keventd_wq); > -#ifdef CONFIG_SMP > - work_on_cpu_wq = create_workqueue("work_on_cpu"); > - BUG_ON(!work_on_cpu_wq); > -#endif > } > _ -- ~Randy -- 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/