Re: device_remove_file and disconnect

From: Greg KH
Date: Sun Jul 24 2005 - 23:26:48 EST

On Thu, Jun 30, 2005 at 10:31:44PM +0200, matthieu castet wrote:
> >Then they should be fixed. Any specific examples?
> >
> >
> I am a little lasy to list all, but some drivers in driver/usb should
> have this problem : the first driver I look : ./misc/phidgetkit.c do
> [1]. So sysfs read don't check if to_usb_interface or usb_get_intfdata
> return NULL pointer...
> And it is a bit your fault, as many developper should have read your
> great tutorial [2] ;)

You are correct, I'll go fix those drivers, thanks for pointing it out.
Others pointed out the same thing this week at OLS :)

> >>Also I always see driver free their privatre data in device disconnect,
> >>so if read/write from sysfs aren't serialized with device disconnect
> >>there are still a possible race like I show in my example.
> >
> >
> >Yes, you are correct. Again, any specific drivers you see with this
> >problem?
> I believe near all drivers that use sysfs via device_create_file, as I
> never see them use mutex in read/write in order to check there aren't in
> the same time in their disconnect that could free there private data
> when they do operation on it...
> Couldn't be possible the make device_remove_file blocking until all the
> open file are closed ?

Hm, do we even know that those files are opened then? I'll poke around
in sysfs and see if we could do that.


greg k-h
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