[PATCH, v10 2/3] hrtimer: implement PR_GET_EFFECTIVE_TIMERSLACK

["Kirill A. Shutemov" <kirill@shutemov.name>]

From: "Kirill A. Shutemov" <kirill@shutemov.name>

PR_GET_EFFECTIVE_TIMERSLACK allows process to know its effective timer
slack value.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
---
 include/linux/prctl.h |    6 ++++++
 kernel/sys.c          |    3 +++
 2 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index a3baeb2..3199458 100644
--- a/include/linux/prctl.h
+++ b/include/linux/prctl.h
@@ -102,4 +102,10 @@
 
 #define PR_MCE_KILL_GET 34
 
+/*
+ * Get effective timerslack value for the process.
+ * It can be higher than PR_GET_TIMERSLACK.
+ */
+#define PR_GET_EFFECTIVE_TIMERSLACK 35
+
 #endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 6fecef0..4b86e41 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1798,6 +1798,9 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 		case PR_GET_TIMERSLACK:
 			error = current->timer_slack_ns;
 			break;
+		case PR_GET_EFFECTIVE_TIMERSLACK:
+			error = task_get_effective_timer_slack(current);
+			break;
 		case PR_SET_TIMERSLACK:
 			if (arg2 <= 0)
 				current->timer_slack_ns =
-- 
1.7.6.3