linux-kernel - [tip:locking/core] locking/pvqspinlock: Don't wait if vCPU is preempted

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Date:   Thu, 12 Jan 2017 02:06:45 -0800
From:   tip-bot for Pan Xinhui <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     hpa@...or.com, xinhui.pan@...ux.vnet.ibm.com,
        torvalds@...ux-foundation.org, peterz@...radead.org,
        linux-kernel@...r.kernel.org, mingo@...nel.org, tglx@...utronix.de
Subject: [tip:locking/core] locking/pvqspinlock: Don't wait if vCPU is
 preempted

Commit-ID:  75437bb304b20a2b350b9a8e9f9238d5e24e12ba
Gitweb:     http://git.kernel.org/tip/75437bb304b20a2b350b9a8e9f9238d5e24e12ba
Author:     Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
AuthorDate: Tue, 10 Jan 2017 02:56:46 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 12 Jan 2017 09:35:57 +0100

locking/pvqspinlock: Don't wait if vCPU is preempted

If prev node is not in running state or its vCPU is preempted, we can give
up our vCPU slices in pv_wait_node() ASAP.

Signed-off-by: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: longman@...hat.com
Link: http://lkml.kernel.org/r/1484035006-6787-1-git-send-email-xinhui.pan@linux.vnet.ibm.com
[ Fixed typos in the changelog, removed ugly linebreak from the code. ]
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/locking/qspinlock_paravirt.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index e3b5520..e6b2f7a 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -263,7 +263,7 @@ pv_wait_early(struct pv_node *prev, int loop)
 	if ((loop & PV_PREV_CHECK_MASK) != 0)
 		return false;
 
-	return READ_ONCE(prev->state) != vcpu_running;
+	return READ_ONCE(prev->state) != vcpu_running || vcpu_is_preempted(prev->cpu);
 }
 
 /*