From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932273AbYD1IvV (ORCPT ); Mon, 28 Apr 2008 04:51:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754052AbYD1IvK (ORCPT ); Mon, 28 Apr 2008 04:51:10 -0400 Received: from DSL212-235-53-3.bb.netvision.net.il ([212.235.53.3]:53132 "EHLO bh-buildlin2.bhalevy.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753858AbYD1IvI (ORCPT ); Mon, 28 Apr 2008 04:51:08 -0400 X-Greylist: delayed 437 seconds by postgrey-1.27 at vger.kernel.org; Mon, 28 Apr 2008 04:51:07 EDT Message-ID: <48158D98.40404@panasas.com> Date: Mon, 28 Apr 2008 11:40:56 +0300 From: Boaz Harrosh User-Agent: Thunderbird 2.0.0.12 (X11/20080213) MIME-Version: 1.0 To: FUJITA Tomonori CC: James.Bottomley@HansenPartnership.com, mingo@elte.hu, akpm@linux-foundation.org, torvalds@linux-foundation.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [GIT PATCH] another tranche of SCSI updates for 2.6.26 References: <20080428013400.GA6245@elte.hu> <1209351113.3801.107.camel@localhost.localdomain> <48157B6A.60307@panasas.com> <20080428173459B.tomof@acm.org> In-Reply-To: <20080428173459B.tomof@acm.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 28 2008 at 11:34 +0300, FUJITA Tomonori wrote: > On Mon, 28 Apr 2008 10:23:22 +0300 > Boaz Harrosh wrote: > >> On Mon, Apr 28 2008 at 5:51 +0300, James Bottomley wrote: >>> On Mon, 2008-04-28 at 03:34 +0200, Ingo Molnar wrote: >>>> * James Bottomley wrote: >>>> >>>>> This represents the tree I had waitin on other mergers. I'm not sure >>>>> this is it, because there are other features (like aic94xx running >>>>> abort) we're racing to get in. >>>>> >>>>> The patch is available at: >>>>> >>>>> master.kernel.org:/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6.git >>>> hm, got this crash with latest -git shortly after i rebased from this >>>> morning's git to this night's git, it looks SCSI related: >>>> >>>> [ 44.513114] Calling initcall 0xc1cece47: init_this_scsi_driver+0x0/0xd0() >>>> [ 47.919053] BUG: unable to handle kernel NULL pointer dereference at 00000004 >>>> [ 47.927035] IP: [] scsi_destroy_command_freelist+0x15/0x5a >>>> [ 47.931008] *pde = 00000000 >>>> [ 47.935253] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC >>>> [ 47.939004] Modules linked in: >>>> [ 47.939004] >>>> [ 47.939004] Pid: 1, comm: swapper Not tainted (2.6.25-sched-devel.git-x86-latest.git #5) >>>> [ 47.939004] EIP: 0060:[] EFLAGS: 00010217 CPU: 0 >>>> [ 47.939004] EIP is at scsi_destroy_command_freelist+0x15/0x5a >>>> [ 47.939004] EAX: c0042000 EBX: 00000000 ECX: c199ba14 EDX: fffffffc >>>> [ 47.939004] ESI: c0042000 EDI: c0042034 EBP: f7c36ebc ESP: f7c36eb0 >>>> [ 47.939004] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 >>>> [ 47.939004] Process swapper (pid: 1, ti=f7c36000 task=f7c4e000 task.ti=f7c36000) >>>> [ 47.939004] Stack: c0042000 00000000 00000000 f7c36ecc c09cfa4c c004225c c1a43378 f7c36ed4 >>>> [ 47.939004] c0688535 f7c36ee8 c04e942b c0042260 c04e93e6 00000330 f7c36ef8 c04e9f20 >>>> [ 47.939004] c004225c 00000002 f7c36f04 c04e9353 c0042000 f7c36f0c c0688aee f7c36f14 >>>> [ 47.939004] Call Trace: >>>> [ 47.939004] [] ? scsi_host_dev_release+0x79/0xa9 >>>> [ 47.939004] [] ? device_release+0x3e/0x54 >>>> [ 47.939004] [] ? kobject_release+0x45/0x55 >>>> [ 47.939004] [] ? kobject_release+0x0/0x55 >>>> [ 47.939004] [] ? kref_put+0x3e/0x49 >>>> [ 47.939004] [] ? kobject_put+0x41/0x46 >>>> [ 47.939004] [] ? put_device+0x16/0x18 >>>> [ 47.939004] [] ? scsi_host_put+0x12/0x14 >>>> [ 47.939004] [] ? scsi_unregister+0x1d/0x20 >>>> [ 47.939004] [] ? aha1542_detect+0x7d1/0x7eb >>>> [ 47.939004] [] ? trace_hardirqs_on+0xb/0xd >>>> [ 47.939004] [] ? init_this_scsi_driver+0xb/0xd0 >>>> [ 47.939004] [] ? ftrace_record_ip+0x1d4/0x1ed >>>> [ 47.939004] [] ? init_this_scsi_driver+0x5e/0xd0 >>>> [ 47.939004] [] ? kernel_init+0x152/0x2b0 >>>> [ 47.939004] [] ? kernel_init+0x0/0x2b0 >>>> [ 47.939004] [] ? kernel_init+0x0/0x2b0 >>>> [ 47.939004] [] ? kernel_thread_helper+0x7/0x10 >>>> [ 47.939004] ======================= >>>> [ 47.939004] Code: ff eb 0c 89 fa 83 c0 04 e8 78 ba b2 ff 31 d2 5b 89 d0 5e 5f 5d c3 55 89 e5 57 56 53 e8 cf d0 74 ff 89 c6 8d 78 34 eb 1c 8d 53 fc <8b> 42 08 8b 4a 04 89 41 04 89 08 89 5a 08 89 5a 04 8b 46 10 e8 >>>> [ 47.939004] EIP: [] scsi_destroy_command_freelist+0x15/0x5a SS:ESP 0068:f7c36eb0 >>> >>> sigh, every time I fix this free list stuff in one place, it breaks in >>> another. This one is caused by the alloc->put sequence for the host (it >>> never got to scsi_add_host() where the freelist is allocated, so we need >>> to not release it in that case). >>> >>> Try this; the signature for an uninitialised free list is easy (both >>> list pointers NULL), so the patch detects that and doesn't try to run >>> over the uninitialised list head. >>> >>> James >>> >>> --- >>> >>> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c >>> index 12d69d7..dc36321 100644 >>> --- a/drivers/scsi/scsi.c >>> +++ b/drivers/scsi/scsi.c >>> @@ -481,6 +481,14 @@ int scsi_setup_command_freelist(struct Scsi_Host *shost) >>> */ >>> void scsi_destroy_command_freelist(struct Scsi_Host *shost) >>> { >>> + if (shost->free_list.next == NULL && shost->free_list.prev == NULL) >>> + /* >>> + * If the next and prev pointers are NULL, that >>> + * means the list was never initialised, so it >>> + * doesn't need freeing >>> + */ >>> + return; >>> + >>> while (!list_empty(&shost->free_list)) { >>> struct scsi_cmnd *cmd; >>> >>> >>> >>> -- >> If we are already on the subject. It looks like we always have at most 1 command in the >> free list, so why the free list at all? or am I reading the code wrong? > > scsi_add_host sets up one free command. If you call scsi_host_alloc > and then scsi_host_put (some LLDs do on their failure path), you hit > the above problem. That was not my question. I understand all about that problem. My question was: We never have more then one command in the free list. So why do we need a free list at all, we can just have a pointer to the extra command at host and thats it. We don't need the all link-list to keep track of just one command Boaz