Thunder from the hill wrote:
>> "As long as I comment [and understand] why I am using the BKL."
>> would be a bit more accurate. How many places in the kernel have
>> you seen comments about what the BKL is actually doing? Could
>> you point me to some of your comments where _you_ are using the
>> BKL? Once you fully understand why it is there, the extra step
>> of removal is usually very small.
>
> Old Blue, could you please bring me an example on where in USB the
> bkl shouldn't be used, but is? And can you explain why it's wrong
> to use bkl there?
Old Blue? 23 isn't _that_ old!
BKL use isn't right or wrong -- it isn't a case of creating a deadlock
or a race. I'm picking a relatively random function from "grep -r
lock_kernel * | grep /usb/". I'll show what I think isn't optimal
about it.
"up" is a local variable. There is no point in protecting its
allocation. If the goal is to protect data inside "up", there should
probably be a subsystem-level lock for all "struct uhci_hcd"s or a
lock contained inside of the structure itself. Is this the kind of
example you're looking for?
static int uhci_proc_open(struct inode *inode, struct file *file)
{
const struct proc_dir_entry *dp = PDE(inode);
struct uhci_hcd *uhci = dp->data;
struct uhci_proc *up;
unsigned long flags;
int ret = -ENOMEM;
- lock_kernel();
up = kmalloc(sizeof(*up), GFP_KERNEL);
if (!up)
goto out;
up->data = kmalloc(MAX_OUTPUT, GFP_KERNEL);
if (!up->data) {
kfree(up);
goto out;
}
+ lock_kernel();
spin_lock_irqsave(&uhci->frame_list_lock, flags);
up->size = uhci_sprint_schedule(uhci, up->data, MAX_OUTPUT);
spin_unlock_irqrestore(&uhci->frame_list_lock, flags);
file->private_data = up;
+
unlock_kernel();
ret = 0;
out:
- unlock_kernel();
return ret;
}
-- Dave Hansen haveblue@us.ibm.com- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sun Jul 07 2002 - 22:00:18 EST