Re: [PATCH 0/2] powerpc/kvm: Enable running guests on RT Linux
From: Paolo Bonzini
Date: Fri Feb 20 2015 - 09:57:57 EST
On 20/02/2015 15:54, Sebastian Andrzej Siewior wrote:
> Usually you see "scheduling while atomic" on -RT and convert them to
> raw locks if it is appropriate.
> Bogdan wrote in 2/2 that he needs to limit the number of CPUs in oder
> not cause a DoS and large latencies in the host. I haven't seen an
> answer to my why question. Because if the conversation leads to
> large latencies in the host then it does not look right.
> Each host PIC has a rawlock and does mostly just mask/unmask and the
> raw lock makes sure the value written is not mixed up due to
> This hardly increase latencies because the "locked" path is very short.
> If this conversation leads to higher latencies then the locked path is
> too long and hardly suitable to become a rawlock.
Yes, but large latencies just mean the code has to be rewritten (x86
doesn't anymore do event injection in an atomic regions for example).
Until it is, using raw_spin_lock is correct.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/