Re: kmalloc without GFP_xxx?

Manfred Spraul
2005-06-29T20:46:01Z

Hi,

One question from Linux-Tag was about the lack of documentation about/in
the kernel. I try to maintain docbook entries when I modify code, even
though I think it's mostly wasted time: Virtually noone reads it anyway,
instead armchair logic on lkml.

Steven wrote:

>Here we see that task 2 can spin with interrupts off, while the first task
>is servicing an interrupt, and God forbid if the IRQ handler sends some
>kind of SMP signal to the CPU running task 2 since that would be a
>deadlock. Granted, this is a hypothetical situation, but makes using
>spin_lock with interrupts enabled a little scary.
>
>
Not, it's not even a hypothetical situation. It's an explicitely
forbidden situation: SMP signals are sent with smp_call_function and the
documentation to that function clearly says:
*
* You must not call this function with disabled interrupts or from a
* hardware interrupt handler or from a bottom half handler.
*/

--
Manfred