sched: Provide is_percpu_thread() helper

Provide a helper function for checking whether current task is a per cpu
thread.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170524081549.541649540@linutronix.de

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2b69fc65020131bed57e41d4b228ed0c59692a5c..3dfa5f99d6ee576630deb7d9644ef97e3f7458dd 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1265,6 +1265,16 @@ extern struct pid *cad_pid;
 #define tsk_used_math(p)                       ((p)->flags & PF_USED_MATH)
 #define used_math()                            tsk_used_math(current)
 
+static inline bool is_percpu_thread(void)
+{
+#ifdef CONFIG_SMP
+       return (current->flags & PF_NO_SETAFFINITY) &&
+               (current->nr_cpus_allowed  == 1);
+#else
+       return true;
+#endif
+}
+
 /* Per-process atomic flags. */
 #define PFA_NO_NEW_PRIVS               0       /* May not gain new privileges. */
 #define PFA_SPREAD_PAGE                        1       /* Spread page cache over cpuset */