5 files changed, 26 insertions, 0 deletions

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 021d8e720c79..23fd8909b9e5 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -170,6 +170,7 @@ extern struct group_info init_groups;
         .cpu_timers     = INIT_CPU_TIMERS(tsk.cpu_timers),              \
         .fs_excl        = ATOMIC_INIT(0),                               \
         .pi_lock        = __SPIN_LOCK_UNLOCKED(tsk.pi_lock),            \
+        .timer_slack_ns = 50000, /* 50 usec default slack */            \
         .pids = {                                                       \
                 [PIDTYPE_PID]  = INIT_PID_LINK(PIDTYPE_PID),            \
                 [PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID),           \
diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index 5ad79198d6f9..48d887e3c6e7 100644
--- a/include/linux/prctl.h
+++ b/include/linux/prctl.h
@@ -78,4 +78,11 @@
 #define PR_GET_SECUREBITS 27
 #define PR_SET_SECUREBITS 28
 
+/*
+ * Get/set the timerslack as used by poll/select/nanosleep
+ * A value of 0 means "use default"
+ */
+#define PR_SET_TIMERSLACK 29
+#define PR_GET_TIMERSLACK 30
+
 #endif /* _LINUX_PRCTL_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3d9120c5ad15..dcc03fd5a7f3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1301,6 +1301,12 @@ struct task_struct {
         int latency_record_count;
         struct latency_record latency_record[LT_SAVECOUNT];
 #endif
+        /*
+         * time slack values; these are used to round up poll() and
+         * select() etc timeout values. These are in nanoseconds.
+         */
+        unsigned long timer_slack_ns;
+        unsigned long default_timer_slack_ns;
 };
 
 /*
diff --git a/kernel/fork.c b/kernel/fork.c
index 7ce2ebe84796..4308d75f0fa5 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -987,6 +987,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         p->prev_utime = cputime_zero;
         p->prev_stime = cputime_zero;
 
+        p->default_timer_slack_ns = current->timer_slack_ns;
+
 #ifdef CONFIG_DETECT_SOFTLOCKUP
         p->last_switch_count = 0;
         p->last_switch_timestamp = 0;
diff --git a/kernel/sys.c b/kernel/sys.c
index 038a7bc0901d..1b96401a0576 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1727,6 +1727,16 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
                 case PR_SET_TSC:
                         error = SET_TSC_CTL(arg2);
                         break;
+                case PR_GET_TIMERSLACK:
+                        error = current->timer_slack_ns;
+                        break;
+                case PR_SET_TIMERSLACK:
+                        if (arg2 <= 0)
+                                current->timer_slack_ns =
+                                        current->default_timer_slack_ns;
+                        else
+                                current->timer_slack_ns = arg2;
+                        break;
                 default:
                         error = -EINVAL;
                         break;