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Date: Sun, 24 Nov 2013 00:36:03 +0100 From: "Rafael J. Wysocki" <rjw@...ysocki.net> To: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Cc: Bjorn Helgaas <bhelgaas@...gle.com>, Tejun Heo <tj@...nel.org>, Mika Westerberg <mika.westerberg@...ux.intel.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "James E.J. Bottomley" <JBottomley@...allels.com> Subject: Re: [PATCH] sysfs: handle duplicate removal attempts in sysfs_remove_group() On Saturday, November 23, 2013 03:07:01 PM Greg Kroah-Hartman wrote: > On Sun, Nov 24, 2013 at 12:12:59AM +0100, Rafael J. Wysocki wrote: > > On Saturday, November 23, 2013 02:53:58 PM Greg Kroah-Hartman wrote: > > > On Sat, Nov 23, 2013 at 11:56:48PM +0100, Rafael J. Wysocki wrote: > > > > On Friday, November 22, 2013 08:43:55 AM Bjorn Helgaas wrote: > > > > > [+cc Rafael, James] > > > > > > > > > > On Tue, Nov 19, 2013 at 11:18 PM, Tejun Heo <tj@...nel.org> wrote: > > > > > > (cc'ing Bjorn) > > > > > > > > > > > > Hello, > > > > > > > > > > > > On Tue, Nov 19, 2013 at 03:09:58PM +0200, Mika Westerberg wrote: > > > > > >> Commit bcdde7e221a8 (sysfs: make __sysfs_remove_dir() recursive) changed > > > > > >> the behavior so that directory removals will be done recursively. This > > > > > >> means that the sysfs group might already be removed if its parent directory > > > > > >> has been removed. > > > > > >> > > > > > >> The current code outputs warnings similar to following log snippet when it > > > > > >> detects that there is no group for the given kobject: > > > > > >> > > > > > >> WARNING: CPU: 0 PID: 4 at fs/sysfs/group.c:214 sysfs_remove_group+0xc6/0xd0() > > > > > >> sysfs group ffffffff81c6f1e0 not found for kobject 'host7' > > > > > >> Modules linked in: > > > > > >> CPU: 0 PID: 4 Comm: kworker/0:0 Not tainted 3.12.0+ #13 > > > > > >> Hardware name: /D33217CK, BIOS GKPPT10H.86A.0042.2013.0422.1439 04/22/2013 > > > > > >> Workqueue: kacpi_hotplug acpi_hotplug_work_fn > > > > > >> 0000000000000009 ffff8801002459b0 ffffffff817daab1 ffff8801002459f8 > > > > > >> ffff8801002459e8 ffffffff810436b8 0000000000000000 ffffffff81c6f1e0 > > > > > >> ffff88006d440358 ffff88006d440188 ffff88006e8b4c28 ffff880100245a48 > > > > > >> Call Trace: > > > > > >> [<ffffffff817daab1>] dump_stack+0x45/0x56 > > > > > >> [<ffffffff810436b8>] warn_slowpath_common+0x78/0xa0 > > > > > >> [<ffffffff81043727>] warn_slowpath_fmt+0x47/0x50 > > > > > >> [<ffffffff811ae526>] sysfs_remove_group+0xc6/0xd0 > > > > > >> [<ffffffff81432f7e>] dpm_sysfs_remove+0x3e/0x50 > > > > > >> [<ffffffff8142a0d0>] device_del+0x40/0x1b0 > > > > > >> [<ffffffff8142a24d>] device_unregister+0xd/0x20 > > > > > >> [<ffffffff8144131a>] scsi_remove_host+0xba/0x110 > > > > > >> [<ffffffff8145f526>] ata_host_detach+0xc6/0x100 > > > > > >> [<ffffffff8145f578>] ata_pci_remove_one+0x18/0x20 > > > > > >> [<ffffffff812e8f48>] pci_device_remove+0x28/0x60 > > > > > >> [<ffffffff8142d854>] __device_release_driver+0x64/0xd0 > > > > > >> [<ffffffff8142d8de>] device_release_driver+0x1e/0x30 > > > > > >> [<ffffffff8142d257>] bus_remove_device+0xf7/0x140 > > > > > >> [<ffffffff8142a1b1>] device_del+0x121/0x1b0 > > > > > >> [<ffffffff812e43d4>] pci_stop_bus_device+0x94/0xa0 > > > > > >> [<ffffffff812e437b>] pci_stop_bus_device+0x3b/0xa0 > > > > > >> [<ffffffff812e437b>] pci_stop_bus_device+0x3b/0xa0 > > > > > >> [<ffffffff812e44dd>] pci_stop_and_remove_bus_device+0xd/0x20 > > > > > >> [<ffffffff812fc743>] trim_stale_devices+0x73/0xe0 > > > > > >> [<ffffffff812fc78b>] trim_stale_devices+0xbb/0xe0 > > > > > >> [<ffffffff812fc78b>] trim_stale_devices+0xbb/0xe0 > > > > > >> [<ffffffff812fcb6e>] acpiphp_check_bridge+0x7e/0xd0 > > > > > >> [<ffffffff812fd90d>] hotplug_event+0xcd/0x160 > > > > > >> [<ffffffff812fd9c5>] hotplug_event_work+0x25/0x60 > > > > > >> [<ffffffff81316749>] acpi_hotplug_work_fn+0x17/0x22 > > > > > >> [<ffffffff8105cf3a>] process_one_work+0x17a/0x430 > > > > > >> [<ffffffff8105db29>] worker_thread+0x119/0x390 > > > > > >> [<ffffffff81063a5d>] kthread+0xcd/0xf0 > > > > > >> [<ffffffff817eb33c>] ret_from_fork+0x7c/0xb0 > > > > > > > > > > > > So, we do have cases where the parent is removed before the child. I > > > > > > suppose the parent pci bridge is removed already? AFAICS this > > > > > > shouldn't break anything but people did seem to expect the removals to > > > > > > be ordered from child to parent. Bjorn, is this something you expect > > > > > > to happened? > > > > > > > > > > I do not expect a PCI bridge to be removed before the devices below > > > > > it. We should be removing all the children before removing the parent > > > > > bridge. > > > > > > > > > > But is this related to PCI? I don't see the connection yet. I tried > > > > > to look into this a bit (my notes are at > > > > > https://bugzilla.kernel.org/show_bug.cgi?id=65281), but I haven't > > > > > figured out the big-picture problem yet. > > > > > > > > OK, so I think I've figured this out. > > > > > > > > As I wrote in the above BZ entry, after the Tejun's patch the > > > > device_del() in pci_stop_dev() removes the subordinate bus object's > > > > "power" directory among other things and because of that the warning > > > > triggers when we do the pci_remove_bus() in pci_remove_bus_device() > > > > for the same device. > > > > > > > > The appended patch fixes it for me, but Greg has already taken the > > > > Mika's one, so this one isn't really necessary. In case you think it > > > > would be useful to apply it anyway, please let me know and I submit it > > > > properly with a changelog etc. > > > > > > I can revert Mika's patch, as it would be good to catch these kinds of > > > errors. > > > > Then we'll need to untangle the SATA/SCSI mess triggered by Bjorn in > > https://bugzilla.kernel.org/show_bug.cgi?id=65281. ;-) > > I have no objection to fixing that, the scsi sysfs handling is "odd" to > say the least... > > If someone can unwind it, that would be great to see happen... Well, if I'm bored to death during the xmas holidays, I may look into that. Till then, I'm afraid it'll stay as is unless there are some really brave people around ... Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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