linux-kernel - [PATCH 1/3] kernel/sched: introduce vcpu preempted check interface

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Date:	Mon, 27 Jun 2016 13:41:28 -0400
From:	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
To:	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:	paulmck@...ux.vnet.ibm.com, peterz@...radead.org, mingo@...hat.com,
	mpe@...erman.id.au, paulus@...ba.org, benh@...nel.crashing.org,
	Waiman.Long@....com, boqun.feng@...il.com, will.deacon@....com,
	dave@...olabs.net, Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Subject: [PATCH 1/3] kernel/sched: introduce vcpu preempted check interface

this supports to fix lock holder preempted issue which run as a guest

for kernel users, we could use bool vcpu_is_preempted(int cpu) to detech
if one vcpu is preempted or not.

The default implementation is a macrodefined by false. So compiler can
wrap it out if arch dose not support such vcpu pteempted check.

archs can implement it by define arch_vcpu_is_preempted().

Signed-off-by: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
---
 include/linux/sched.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6e42ada..dc0a9c3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -3293,6 +3293,15 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
 
 #endif /* CONFIG_SMP */
 
+#ifdef arch_vcpu_is_preempted
+static inline bool vcpu_is_preempted(int cpu)
+{
+	return arch_vcpu_is_preempted(cpu);
+}
+#else
+#define vcpu_is_preempted(cpu)	false
+#endif
+
 extern long sched_setaffinity(pid_t pid, const struct cpumask *new_mask);
 extern long sched_getaffinity(pid_t pid, struct cpumask *mask);
 
-- 
2.4.11