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Groups > linux.kernel > #1447679

[PATCH v3 1/4] kernel/sched: introduce vcpu preempted check interface

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This patch supports to fix lock holder preemption issue.

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 macro defined by false. So compiler can
wrap it out if arch dose not support such vcpu pteempted check.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
 include/linux/sched.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6e42ada..cbe0574 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -3293,6 +3293,18 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
 
 #endif /* CONFIG_SMP */
 
+/*
+ * In order to deal with a various lock holder preemption issues provide an
+ * interface to see if a vCPU is currently running or not.
+ *
+ * This allows us to terminate optimistic spin loops and block, analogous to
+ * the native optimistic spin heuristic of testing if the lock owner task is
+ * running or not.
+ */
+#ifndef vcpu_is_preempted
+#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

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Thread

[PATCH v3 0/4] implement vcpu preempted check Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-07-21 09:50 +0200
  [PATCH v3 1/4] kernel/sched: introduce vcpu preempted check interface Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-07-21 09:50 +0200
  [PATCH v3 2/4] powerpc/spinlock: support vcpu preempted check Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-07-21 09:50 +0200
  [PATCH v3 4/4] kernel/locking: Drop the overhead of {mutex,rwsem}_spin_on_owner Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-07-21 09:50 +0200
  [PATCH v3 3/4] locking/osq: Drop the overhead of osq_lock() Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-07-21 09:50 +0200

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