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authorPan Xinhui <[email protected]>2016-11-02 05:08:28 -0400
committerIngo Molnar <[email protected]>2016-11-22 12:48:05 +0100
commitd9345c65eb7930ac6755cf593ee7686f4029ccf4 (patch)
tree997e488123a15a9725bd6c6ee454500f4b63a66d
parent02cb689b2c102178c83e763e4f34b3efe7f969e2 (diff)
sched/core: Introduce the vcpu_is_preempted(cpu) interface
This patch is the first step to add support to improve lock holder preemption beaviour. vcpu_is_preempted(cpu) does the obvious thing: it tells us whether a vCPU is preempted or not. Defaults to false on architectures that don't support it. Suggested-by: Peter Zijlstra (Intel) <[email protected]> Tested-by: Juergen Gross <[email protected]> Signed-off-by: Pan Xinhui <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> [ Translated the changelog to English. ] Acked-by: Christian Borntraeger <[email protected]> Acked-by: Paolo Bonzini <[email protected]> Cc: [email protected] Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
-rw-r--r--include/linux/sched.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index dc37cbe2b13c..37261afbf16a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -3510,6 +3510,18 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
#endif /* CONFIG_SMP */
+/*
+ * In order to reduce various lock holder preemption latencies 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);