Re: BUG or not? GFP_KERNEL with interrupts disabled.

[Linus Torvalds <torvalds@xxxxxxxxxxxxx>]

On Thu, 27 Mar 2003, Dan Eble wrote:
> 
> 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?

Yeah. It should also probably use "in_atomic()" instead of 
"in_interrupt()", since that also finds people who have marked themselves 
non-preemptible.

So what the test SHOULD look like is this:

        if (gfp_mask & __GFP_WAIT) {
                if (in_atomic() || irqs_disabled()) {
                        static int count = 0;
                        ...
                }
        }

which should catch all the cases we really care about.

                Linus