Andi Kleen wrote:
On Friday 16 June 2006 12:26, KAMEZAWA Hiroyuki wrote:
On 16 Jun 2006 11:14:57 +0200
Andi Kleen <[email protected]> wrote:
KAMEZAWA Hiroyuki <[email protected]> writes:
This is a bit pessimistic. But forecd migration of RT task which is bounded
to the special cpu will cause unpredictable trouble, I think.
More trouble than running it on a CPU that is about to fail?
Doubtful.
With my patch, RT tasks will continute to run.
That's the problem - if the CPU is failing and you have to remove
it the task will likely corrupt its data or fail in other ways
if it doesn't allow it.
Better to let RT tasks run a little slower on another CPU.
Assume there are some multi-threaded tasks with SCHED_FIFO.
If they uses some kind of synchronization in user land and task is migrated to
other cpus, it will cause dead-lock.
If its CPU fails much worse things than that will happen.
One way might be to break affinity of all processes in the system on hot unplug
- then your deadlock would be avoided - but it might be a bit radical.
Agreed. The kernel is just doing some basic fallback behaviour. If you
actually have a critical RT system, you probably need to have much more
sophisticated handling of CPU unplug anyway. So it doesn't make much
sense to complicate the kernel for this.
--
SUSE Labs, Novell Inc.
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