Re: Spinlocks, intr levels et al

[Manfred Spraul]

Kanoj Sarcar wrote:
> >
> > This is only reliable if there is only _one_ such spinlock. As soon as
> > you have 2 users, you have a lock-up.
> >
> 
> I can not follow your scenario, please give an example, involving
> cpu1, cpu2 etc, L1, L2 etc. Here is what the proposed
> spin_lock_irqsave_intercpu() function looks like in theory:
> 

cpu1:			cpu2:
spin_lock_irqsave_intercpu(&L1);
			spin_lock_irqsave_intercpu(&L2);

; now both cpu's have disabled their interrupt flags.

send_ipi_to_other_cpu_and_wait_until_it_has_arrived();
			send_ipi_to_other_cpu_and \
			  _wait_until_it_has_arrived();

; will sleep forever.

eg. flush_tlb_all() uses this send_ipi_to_other_cpu_and_wait().

--
	Manfred