On Thu, 27 Mar 2003, Linus Torvalds wrote:
>
> On Thu, 27 Mar 2003, David S. Miller wrote:
> >
> > Ok, so can we add a:
> >
> > if (irqs_disabled())
> > BUG();
> >
> > check to do_softirq()?
>
> I'd suggest making it a counting warning (with a static counter per
> local-bh-enable macro expansion) and adding it to local_bh_enable() -
> otherwise it will only BUG() when the (potentially rare) condition
> happens - instead of always giving a nice backtrace of exact problem
> spots.
So, to return to my original question... local_bh_count() > 0 when
a BH is running or after local_bh_disable(). local_irq_count() > 0 in
interrupt context, but not necessarily when interrupts are disabled.
This makes checks like the following (in alloc_skb) asymmetric:
if (in_interrupt() && (gfp_mask & __GFP_WAIT)) {
static int count = 0;
if (++count < 5) {
printk(KERN_ERR "alloc_skb called nonatomically "
"from interrupt %p\n", NET_CALLER(size));
BUG();
In a driver I'm writing, this bug was hidden until I switched from using
write_lock_irqsave() to write_lock_bh(). Shouldn't this bug also be
announced if interrupts are disabled? (I understand that disabling bh/irq
in the correct order will ensure that this bug is properly detected, but
it seems like a strange policy to rely on correct coding to catch a bug.)
--
Dan Eble <dane@xxxxxxxxxx> _____ .
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