Re: device_remove_file and disconnect

[matthieu castet <castet.matthieu@free.fr>]

Hi,
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] ;)
>
> > > 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 ?
>
> thanks,
>
> Matthieu
>
> [1]
> #define show_input(value)       \
> static ssize_t show_input##value(struct device *dev, char *buf) \
> {                                                                       \
>         struct usb_interface *intf = to_usb_interface(dev);             \
>         struct phidget_interfacekit *kit = usb_get_intfdata(intf);      \
>                                                                         \
>         return sprintf(buf, "%d\n", kit->inputs[value - 1]);            \
> }                                                                       \
> static DEVICE_ATTR(input##value, S_IRUGO, show_input##value, NULL);
>
> [2] http://www.linuxjournal.com/article/7353

So will there be a fix in the kernel, or all this driver are broken and 
should be fixed ?

thanks

Matthieu
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