Messages in this thread | | | Date | Sat, 14 Dec 2013 09:24:19 -0800 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH 0/4] treewide: add missing put_device calls |
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On Fri, Dec 13, 2013 at 01:42:05PM -0700, Bjorn Helgaas wrote: > [+cc Greg] > > On Fri, Dec 13, 2013 at 12:22 PM, Levente Kurusa <levex@linux.com> wrote: > > Hi, > > > > This is just the beginning of patchset-set that aims to fix possible > > problems caused by not calling put_device() if device_register() fails. > > > > The root cause for the need to call put_device() is that the underlying > > kobject still has a reference count of 1. Thus, device.release() will not > > be called and the device will just sit there waiting for a put_device(). > > Adding the put_device() also removes the need for the call to kfree() as most > > release functions already call kfree() on the container of the device. > > > > While these have not been experienced, they are potential issues and thus > > they need to be fixed. Also, they are a few more files that have the same > > kind of issue, those will be fixed if these are accepted. > > Thanks for doing this. This is the sort of mistake that just gets > copied everywhere, so fixing the examples in the tree will help > prevent the problem from spreading more. > > I don't know if there's really value in having device_register() > return an error but rely on the caller to do the put_device(). Are > there cases where the caller still needs the struct device even if > device_register() fails? E.g., could we do something like this > instead (I know some callers would also require corresponding changes > to avoid double puts):
Yeah, that might make more sense, but I was trying to not have the driver core suddenly free memory if something you pass to it goes wrong. That's a pretty "odd" thing for an api call to do in the kernel, usually the caller is always responsible for cleaning up for errors happening.
And there's going to be a ton of changes to get this fixed, as you really need to do it all in one patch, which makes for a bad "flag-day" of the api.
thanks,
greg k-h
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