linux-kernel - [PATCH 2/5] stop_machine: yield CPU during stop machine

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Message-Id: <1477051138-1610-3-git-send-email-borntraeger@de.ibm.com>
Date:   Fri, 21 Oct 2016 13:58:55 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Nicholas Piggin <npiggin@...il.com>, linux-kernel@...r.kernel.org,
        linux-s390 <linux-s390@...r.kernel.org>,
        linux-arch@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Noam Camus <noamc@...hip.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
Subject: [PATCH 2/5] stop_machine: yield CPU during stop machine

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.

Signed-off-by: Christian Borntraeger <borntraeger@...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