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

Juergen Gross
2016-10-21T12:41:53Z

On 21/10/16 14:05, Peter Zijlstra wrote:
> 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.

Corrected xen-devel mail address.

Juergen

>
>> 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
>>
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