Re: [PATCH 1/2] serial: 8250: Initialize pointer to irq_info

From: Andrew Morton
Date: Thu Aug 19 2010 - 19:44:19 EST


On Tue, 17 Aug 2010 09:17:20 +0100
Alan Cox <alan@xxxxxxxxxxxxxxx> wrote:

> On Tue, 17 Aug 2010 09:59:06 +0200
> Michal Simek <monstr@xxxxxxxxx> wrote:
>
> > Initialize "i" irq_info pointer in serial_unlink_irq_chain.
> >
> > Compilation warning:
> > CC drivers/serial/8250.o
> > drivers/serial/8250.c: In function 'serial8250_shutdown':
> > drivers/serial/8250.c:1701: warning: 'i' may be used uninitialized in
> > this function
>
> NAK (again)
>
> Use a newer compiler - modern ones get this right.

: 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);

How can any compiler possibly determine that the hlist_for_each() is
never executed zero times?

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