Linus Torvalds wrote:
> In practice, there are places that know how spinlocks work, and do things
> with them that would be illegal in the preemptive UP kernel. Nor many, and
> maybe I'm pessimistic, but I would not be in the least surprised if some
> random driver somewhere does something like
>
> spin_lock_irq(&io_request_lock);
> ...
> spin_unlock(&io_request_lock);
> ...
> __sti();
>
> which is entirely legal on SMP. But it would be hugely illegal on threaded
> UP with the spinlock optimizations, because the "unlock" would modify the
> spinlock count, but the optimzied "lock_irq" would not.
At least those things are easily caught with some spinlock debugging code.
-- Jamie
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This archive was generated by hypermail 2b29 : Thu Mar 23 2000 - 21:00:35 EST