Re: device_remove_file and disconnect

From: matthieu castet (castet.matthieu_at_free.fr)
Date: 07/03/05

  • Next message: Daniel Drake: "Re: Problem with inotify" 
    Date:	Sun, 03 Jul 2005 01:27:53 +0200
To: Greg KH <greg@kroah.com>

    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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  • Next message: Daniel Drake: "Re: Problem with inotify"

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