From: Patrick Mansfield <patmans@us.ibm.com>
To: Greg KH <greg@kroah.com>
Cc: linux-kernel@vger.kernel.org, mochel@digitalimplant.org,
linux-scsi@vger.kernel.org
Subject: Re: [PATCH] Use device_for_each_child() to unregister devices in scsi_remove_target().
Date: Mon, 11 Jul 2005 17:56:33 -0700 [thread overview]
Message-ID: <20050712005633.GA453@us.ibm.com> (raw)
In-Reply-To: <20050712002011.GA9331@kroah.com>
On Mon, Jul 11, 2005 at 05:20:12PM -0700, Greg KH wrote:
> On Tue, Jul 05, 2005 at 05:38:50PM -0700, Patrick Mansfield wrote:
> > Hi Greg / Patrick -
> >
> > I'm getting an oops with current (pulled today) 2.6 git, the
> > device_for_each_child() does not seem to be deletion safe.
> >
> > We hold the klist in place via the n_ref, but the kobj (in the struct
> > device for the struct scsi_target) containing it is freed when the
> > kref->refcount goes to zero.
>
> But we grab a reference to that object right before we call
> device_for_each_child(), right? Or am I missing something here?
No, we get another reference on the passed in dev argument (in this
failing case, it is for an FC's rport), not its children (scsi_target)
that we want to iterate over.
If all children (scsi_targets) are removed, then the put in
scsi_remove_target() would (or could) set the rport refcount to zero and
it would be deleted. But the scsi_target would already be gone.
Cases that are not affected are passed a scsi_target:
scsi_is_target_device(dev) is true and we won't even call
device_for_each_child().
Adding another get/put in __remove_child() does *not* help either, as it
is the code within device_for_each_child() that needs another get/put of
the kref instead of a get/put on the klist (well its n_ref); and if you do
that, I don't see how the locking can be done correctly.
I thought we had some semaphores in scsi to protect calls to
scsi_remove_target(), but I only see those for scsi_device scan/removal
(the shost->scan_mutex).
It looks like scsi should not allow removal and additions to happen at the
same time on any scsi_target (and adding up/down on shost->scan_mutex
won't fix this problem).
-- Patrick Mansfield
next prev parent reply other threads:[~2005-07-12 0:59 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-20 22:55 [GIT PATCH] Driver core changes for 2.6.12 Greg KH
2005-06-20 22:59 ` [PATCH] sysfs_{create|remove}_link should take const char * Greg KH
2005-06-20 22:59 ` [PATCH] kobject_hotplug() should use kobject_name() Greg KH
2005-06-20 22:59 ` [PATCH] Make kobject's name be const char * Greg KH
2005-06-20 22:59 ` [PATCH] kset_hotplug_ops->name shoudl return " Greg KH
2005-06-20 22:59 ` [PATCH] make driver's name be " Greg KH
2005-06-20 22:59 ` [PATCH] Make attributes names " Greg KH
2005-06-20 22:59 ` [PATCH] sysfs: (driver/base) if show/store is missing return -EIO Greg KH
2005-06-20 22:59 ` [PATCH] sysfs: " Greg KH
2005-06-20 22:59 ` [PATCH] sysfs: (driver/pci) " Greg KH
2005-06-20 22:59 ` [PATCH] sysfs: (driver/block) " Greg KH
2005-06-20 22:59 ` [PATCH] sysfs: (rest) " Greg KH
2005-06-20 22:59 ` [PATCH] INPUT: move to use the new class code, instead of class_simple Greg KH
2005-06-20 22:59 ` [PATCH] tty: " Greg KH
2005-06-20 22:59 ` [PATCH] CLASS: move a "simple" class logic into the class core Greg KH
2005-06-20 22:59 ` [PATCH] class: convert sound/* to use the new class api instead of class_simple Greg KH
2005-06-20 22:59 ` [PATCH] USB: move the usb hcd code to use the new class code Greg KH
2005-06-20 22:59 ` [PATCH] class: convert drivers/block/* to use the new class api instead of class_simple Greg KH
2005-06-20 22:59 ` [PATCH] class: convert drivers/ieee1394/* " Greg KH
2005-06-20 22:59 ` [PATCH] class: convert drivers/char/* " Greg KH
2005-06-20 22:59 ` [PATCH] class: convert drivers/scsi/* " Greg KH
2005-06-20 22:59 ` [PATCH] class: convert drivers/* " Greg KH
2005-06-20 22:59 ` [PATCH] USB: trivial error path fix Greg KH
2005-06-20 22:59 ` [PATCH] class: convert arch/* to use the new class api instead of class_simple Greg KH
2005-06-20 22:59 ` [PATCH] class: convert the remaining class_simple users in the kernel to usee the new class api Greg KH
2005-06-20 22:59 ` [PATCH] class: add kerneldoc for the new class functions Greg KH
2005-06-20 22:59 ` [PATCH] class: remove class_simple code, as no one in the tree is using it anymore Greg KH
2005-06-20 22:59 ` [PATCH] fix "make mandocs" after class_simple.c removal Greg KH
2005-06-20 22:59 ` [PATCH] Add a semaphore to struct device to synchronize calls to its driver Greg KH
2005-06-20 22:59 ` [PATCH] fix up ipmi code after class_simple.c removal Greg KH
2005-06-20 22:59 ` [PATCH] Move device/driver code to drivers/base/dd.c Greg KH
2005-06-20 22:59 ` [PATCH] Use driver_for_each_device() instead of manually walking list Greg KH
2005-06-20 22:59 ` [PATCH] Use driver_for_each_device() in drivers/pnp/driver.c " Greg KH
2005-06-20 22:59 ` [PATCH] Add driver_for_each_device() Greg KH
2005-06-20 22:59 ` [PATCH] Add a klist to struct bus_type for its drivers Greg KH
2005-06-20 22:59 ` [PATCH] Add a klist to struct bus_type for its devices Greg KH
2005-06-20 22:59 ` [PATCH] Add initial implementation of klist helpers Greg KH
2005-06-20 22:59 ` [PATCH] Add a klist to struct device_driver for the devices bound to it Greg KH
2005-06-20 22:59 ` [PATCH] Remove the unused device_find() Greg KH
2005-06-20 22:59 ` [PATCH] Use bus_for_each_{dev,drv} for driver binding Greg KH
2005-06-20 22:59 ` [PATCH] add klist_node_attached() to determine if a node is on a list or not Greg KH
2005-06-20 22:59 ` [PATCH] Fix up USB to use klist_node_attached() instead of list_empty() on lists that will go away Greg KH
2005-06-20 22:59 ` [PATCH] Remove struct device::driver_list Greg KH
2005-06-20 22:59 ` [PATCH] Fix up bus code and remove use of rwsem Greg KH
2005-06-20 22:59 ` [PATCH] Remove struct device::bus_list Greg KH
2005-06-20 22:59 ` [PATCH] Don't reference NULL klist pointer in klist_remove() Greg KH
2005-06-20 22:59 ` [PATCH] Call klist_del() instead of klist_remove() Greg KH
2005-06-20 22:59 ` [PATCH] Use device_for_each_child() to unregister devices in scsi_remove_target() Greg KH
2005-06-20 22:59 ` [PATCH] use device_for_each_child() to properly access child devices Greg KH
2005-06-20 22:59 ` [PATCH] Use a klist for device child lists Greg KH
2005-06-20 22:59 ` [PATCH] Fix up bogus comment Greg KH
2005-06-20 22:59 ` [PATCH] driver core: change export symbol for driver_for_each_device() Greg KH
2005-06-20 22:59 ` [PATCH] Use device_for_each_child() to unregister devices in nodemgr_remove_host_dev() Greg KH
2005-06-20 22:59 ` [PATCH] use device_for_each_child() to properly access child devices Greg KH
2005-06-20 22:59 ` [PATCH] USB: fix build warning in usb core as pointed out by Andrew Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: fix bk-driver-core kills ppc64 Greg KH
2005-06-20 22:59 ` [PATCH] Fix typo in scdrv_init() Greg KH
2005-06-20 22:59 ` [PATCH] Driver core: Fix up the driver and device iterators to be quieter Greg KH
2005-06-20 22:59 ` [PATCH] usb: klist_node_attached() fix Greg KH
2005-06-20 22:59 ` [PATCH] sn: fixes due to driver core changes Greg KH
2005-06-20 22:59 ` [PATCH] driver core: Fix races in driver_detach() Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: driver model doc update Greg KH
2005-06-20 22:59 ` [PATCH] Driver core: unregister_node() for hotplug use Greg KH
2005-06-20 22:59 ` [PATCH] usbcore: Don't call device_release_driver recursively Greg KH
2005-06-20 22:59 ` [PATCH] libfs: add simple attribute files Greg KH
2005-06-20 22:59 ` [PATCH] Driver core: change device_attribute callbacks Greg KH
2005-06-20 22:59 ` [PATCH] driver core: fix error handling in bus_add_device Greg KH
2005-06-20 22:59 ` [PATCH] Driver core: Documentation: update device attribute callbacks Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: drivers/base - drivers/i2c/chips/adm1026.c: " Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: arch: " Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: drivers/i2c/chips/adm1031.c - lm75.c: " Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: drivers/i2c/chips/lm77.c - max1619.c: " Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: drivers/i2c/chips/pc87360.c - w83627hf.c: " Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: drivers/char/raw3270.c - drivers/net/netiucv.c: " Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: drivers/i2c/chips/w83781d.c - drivers/s390/block/dcssblk.c: " Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: drivers/usb/input/aiptek.c - drivers/zorro/zorro-sysfs.c: " Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: drivers/s390/net/qeth_sys.c - drivers/usb/gadget/pxa2xx_udc.c: " Greg KH
2005-06-20 22:59 ` [PATCH] Driver Core: include: " Greg KH
2005-06-20 22:59 ` [PATCH] I2C: drivers/i2c/chips/adm1026.c: use dynamic sysfs callbacks Greg KH
2005-06-20 22:59 ` [PATCH] I2C: add i2c sensor_device_attribute and macros Greg KH
2005-06-20 22:59 ` [PATCH] sysfs-iattr: attach sysfs_dirent before new inode Greg KH
2005-06-20 22:59 ` [PATCH] Driver core: Don't "lose" devices on suspend on failure Greg KH
2005-06-20 22:59 ` [PATCH] sysfs-iattr: set inode attributes Greg KH
2005-06-20 22:59 ` [PATCH] sysfs-iattr: add sysfs_setattr Greg KH
2005-06-20 22:59 ` [PATCH] SYSFS: fix PAGE_SIZE check Greg KH
2005-06-20 22:59 ` [PATCH] USB: fix show_modalias() function due to attribute change Greg KH
2005-06-20 22:59 ` [PATCH] PCI: " Greg KH
2005-07-06 0:38 ` [PATCH] Use device_for_each_child() to unregister devices in scsi_remove_target() Patrick Mansfield
2005-07-12 0:20 ` Greg KH
2005-07-12 0:56 ` Patrick Mansfield [this message]
2005-06-21 11:42 ` [PATCH] Add initial implementation of klist helpers Rik van Riel
2005-06-21 23:13 ` Greg KH
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