At Thu, 5 Oct 2006 15:54:47 +0200,
Karsten Wiese wrote:
>
> snd_disconnected_file, virtual device
>
> On response to "usb disconnect" an usb-soundcard manipulates
> that snd_card's file's f_ops to only allow release
> by calling this virtual device's
> void snd_disconnect_file(struct file *file).
> After release is actually called, the virtual device instance is freed.
>
> Signed-off-by: Karsten Wiese <fzu@xxxxxxxxxxxxxxxxxxxxx>
Thanks, the code looks better.
> +void snd_disconnect_file(struct file *file)
> +{
> + struct snd_disconnected_file *df;
> + df = kmalloc(sizeof(struct snd_disconnected_file), GFP_KERNEL);
> + if (df == NULL)
> + panic("Atomic allocation failed for snd_disconnected_file!");
The message doesn't match...
Some people prefer "if (!df)" although I myself don't mind at all.
> +
> + df->file = file;
> + df->f_op = file->f_op;
> +
> + mutex_lock(&mutex);
> + list_add(&df->list, &disconnected_files);
> + mutex_unlock(&mutex);
> +
> + fops_get(&snd_disconnect_f_ops);
> + file->f_op = &snd_disconnect_f_ops;
> + printk(KERN_INFO "%s rc3\n", __FUNCTION__);
This will be removed in the final version, right?
> +}
My only concern is whether the release of the old f_op can be called
at the same time during snd_disconnect_file(). If this can happen,
it's racy and results in a memory leak.
Could you check whether this scenario could be true? For example,
insert ssleep(10) after kmalloc so that you have a chance to close the
app manually during disconnect is called. Mmaybe better to add a
debug printk in the original release f_ops, too.
Takashi
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