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

[tip-bot for Pan Xinhui]

Commit-ID:  75437bb304b20a2b350b9a8e9f9238d5e24e12ba
Gitweb:     http://git.kernel.org/tip/75437bb304b20a2b350b9a8e9f9238d5e24e12ba
Author:     Pan Xinhui <xinhui.pan@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue, 10 Jan 2017 02:56:46 -0500
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: longman@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1484035006-6787-1-git-send-email-xinhui.pan@xxxxxxxxxxxxxxxxxx
[ Fixed typos in the changelog, removed ugly linebreak from the code. ]
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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);
 }
 
 /*