Messages in this thread | | | Date | Wed, 10 Feb 2010 09:56:31 +0800 | Subject | Re: [PATCH] sysfs: differentiate between locking links and non-links | From | Américo Wang <> |
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On Wed, Feb 10, 2010 at 9:21 AM, David Rientjes <rientjes@google.com> wrote: > On Wed, 10 Feb 2010, Neil Brown wrote: > >> commit 2e502cfe444b68f6ef6b8b2abe83b6112564095b >> Author: NeilBrown <neilb@suse.de> >> Date: Wed Feb 10 09:43:45 2010 +1100 >> >> sysfs: differentiate between locking links and non-links for sysfs >> >> symlinks and non-symlink is sysfs are very different. >> A symlink can never be locked (active) while an attribute >> modification routine is running. So removing symlink from an >> attribute 'store' routine should be permitted without any lockdep >> warnings. >> >> So split the lockdep context for 's_active' in two, one for symlinks >> and other for everything else. >> > > What happens for hard links such as writing to > /sys/devices/block/xxx/queue/scheduler to change an I/O scheduler which > requires sd->dep_map and sd->parent->dep_map in sysfs_get_active_two() to > pin both? The call to kobject_del() invokes the destruction that also > requires sd->dep_map in sysfs_deactivate() because of the s_active lockdep > annotation. >
This is not related with Neil's case at all.
The I/O scheduler switch case should be a bogus, I am working on it. We have more similar cases of cpu hotplug. Trust me, I am working on a fix to all of them, this is not as easy as you may think about.
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