Messages in this thread | | | Date | Thu, 27 Mar 2003 14:02:20 -0500 (EST) | From | Dan Eble <> | Subject | Re: BUG or not? GFP_KERNEL with interrupts disabled. |
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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@aiinet.com> _____ . | _ |/| Applied Innovation Inc. | |_| | | http://www.aiinet.com/ |__/|_|_|
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