From: Grygorii Strashko <Grygorii.Strashko@linaro.org>
Date: Tue, 21 Jul 2015 19:43:56 +0300
Subject: pid.h: include atomic.h
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.25-rt16.tar.xz

This patch fixes build error:
  CC      kernel/pid_namespace.o
In file included from kernel/pid_namespace.c:11:0:
include/linux/pid.h: In function 'get_pid':
include/linux/pid.h:78:3: error: implicit declaration of function 'atomic_inc' [-Werror=implicit-function-declaration]
   atomic_inc(&pid->count);
   ^
which happens when
 CONFIG_PROVE_LOCKING=n
 CONFIG_DEBUG_SPINLOCK=n
 CONFIG_DEBUG_MUTEXES=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_PID_NS=y

Vanilla gets this via spinlock.h.

Signed-off-by: Grygorii Strashko <Grygorii.Strashko@linaro.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/linux/pid.h |    1 +
 1 file changed, 1 insertion(+)

--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -3,6 +3,7 @@
 #define _LINUX_PID_H
 
 #include <linux/rculist.h>
+#include <linux/atomic.h>
 
 enum pid_type
 {