lkml.org 
[lkml]   [2009]   [Jun]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [Compile Warning] 2.6.30-rc8 build
Date
On Fri June 5 2009, Roland Dreier wrote:
> > To my reading of the function, I think gcc has a point:
> >
> > drivers/serial/8250.c: In function 'serial8250_shutdown':
> > drivers/serial/8250.c:1685: warning: 'i' may be used uninitialized in this function
> >
> > It does read as if the code might try to initialize
> > the 'lock' field of a null pointer.
>
> The code in question is:
>
> static void serial_unlink_irq_chain(struct uart_8250_port *up)
> {
> struct irq_info *i;
> struct hlist_node *n;
> struct hlist_head *h;
>
> mutex_lock(&hash_mutex);
>
> h = &irq_lists[up->port.irq % NR_IRQ_HASH];
>
> hlist_for_each(n, h) {
> i = hlist_entry(n, struct irq_info, node);
> if (i->irq == up->port.irq)
> break;
> }
>
> BUG_ON(n == NULL);
> BUG_ON(i->head == NULL);
>
> if (list_empty(i->head))
> free_irq(up->port.irq, i);
>
> and if the hlist_for_each() doesn't find a matching irq_info to put in
> i, then the BUG_ON(n == NULL) will kill the system. So there's no bug
> although it is understandable that gcc can't see that.
>
> (Not sure why you talk about "the 'lock' field of a null pointer" -- I
> assume your gcc warns about the function serial8250_shutdown() because
> it is inlining a function only called from a single location)
>

Later in the code that gcc thought had the problem - -
where it tries to do a spinlock_init(i->lock).

Of course, I, just like gcc, did not know the machine had already died.
I'll stick an "i = something" at the top (NULL?) just to shut up gcc.

Mike
> - R.
>
>




\
 
 \ /
  Last update: 2009-06-05 19:43    [W:2.051 / U:0.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site