Re: [PATCH 2/5] stop_machine: yield CPU during stop machine

Peter Zijlstra
2016-10-21T12:05:49Z

On Fri, Oct 21, 2016 at 01:58:55PM +0200, Christian Borntraeger wrote:
> stop_machine can take a very long time if the hypervisor does
> overcommitment for guest CPUs. When waiting for "the one", lets
> give up our CPU by using the new cpu_relax_yield.

This seems something that would apply to most other virt stuff. Lets Cc
a few more lists for that.

> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
> kernel/stop_machine.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
> index ec9ab2f..1eb8266 100644
> --- a/kernel/stop_machine.c
> +++ b/kernel/stop_machine.c
> @@ -194,7 +194,7 @@ static int multi_cpu_stop(void *data)
> /* Simple state machine */
> do {
> /* Chill out and ensure we re-read multi_stop_state. */
> - cpu_relax();
> + cpu_relax_yield();
> if (msdata->state != curstate) {
> curstate = msdata->state;
> switch (curstate) {
> --
> 2.5.5
>