> CPU1 CPU2
> spin_lock_irq() -> __cli()
> /* irq locally disabled */
> lock_kernel() (kernel_flag
> acquired)
> flush_tlb_page()
> lock_kernel();
> /* spin on the lock with irq
> disabled */
> send IPI
> /* never execute
> smp_invalidate irq */
> /* deadlock */
>
> Right now to avoid this scenario we must simply never call lock_kernel()
> with irq disabled.
ugh, some time ago i added a 'sti' to lock_kernel() for exactly this
reason. The bug got reintroduced when we switched to a spin_lock()-ed
kernel lock.
> I changed also a bit also the way we send the tlb flush. I resolved the
> locking quite easily since I am delivering an NMI to all other CPUS. The
> only necessary enforcement is that all calls to smp_flush_tlb _must_ be
> serialized by some kind of lock, currently the big kernel lock.
as i said in the previous mail, _dont_ do this Andrea. At least not in
2.2. This way we might trigger CPU bugs never seen before.
-- mingo
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