| Message ID | 1477386195-32736-3-git-send-email-borntraeger@de.ibm.com |
|---|---|
| State | Not Applicable |
| Delegated to: | David Miller |
| Headers | show |
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) {
Some time ago commit 57f2ffe14fd125c2 ("s390: remove diag 44 calls from cpu_relax()") did stop cpu_relax on s390 yielding to the hypervisor. As it turns out this made stop_machine run really slow on virtualized overcommited systems. For example the kprobes test during bootup took several seconds instead of just running unnoticed with large guests. Therefore, the yielding was reintroduced with commit 4d92f50249eb ("s390: reintroduce diag 44 calls for cpu_relax()"), but in fact the stop machine code seems to be the only place where this yielding was really necessary. This place is probably the most important one as it makes all but one guest CPUs wait for one guest CPU. As we now have cpu_relax_yield, we can use this in multi_cpu_stop. For now lets only add it here. We can add it later in other places when necessary. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> --- kernel/stop_machine.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)