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Date: Thu, 27 Mar 2003 11:08:26 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: Dan Eble <dane@aiinet.com>
cc: "David S. Miller" <davem@redhat.com>, <shmulik.hen@intel.com>,
       <bonding-devel@lists.sourceforge.net>,
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Subject: Re: BUG or not? GFP_KERNEL with interrupts disabled.
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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

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