Messages in this thread | | | Subject | Re: [linux-usb-devel] [PATCH] back out sysfs reference count change | From | Benjamin Herrenschmidt <> | Date | Wed, 31 Mar 2004 12:11:30 +1000 |
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On Wed, 2004-03-31 at 09:55, Greg KH wrote: > Hi, > > The patch below backs out Maneesh's sysfs patch that was recently added > to the kernel. In its defense, the original patch did solve some fixes > that could be duplicated on SMP machines, but the side affect of the > patch caused lots of problems. Basically it caused kobjects to get > their references incremented when files that are not present in the > kobject are asked for (udev can easily trigger this when it looks for > files call "dev" in directories that do not have that file). This can > cause easy oopses when the VFS later ages out those old dentries and the > kobject has its reference finally released (usually after the module > that the kobject lived in was removed.)
I think that the bug in the first place is to have an existing kobject that didn't bump the module ref count.
If a kobject exists that have a pointer to the module code (the release function), it _MUST_ have bumped the module ref count, that's the whole point of the module reference count.
If rmmod blocks forever because that kobject has a stale reference, that's a different problem, but khubd should not be involved in that process and should definitely not be blocked and not wait for the kobject to go away.
Ben.
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