select: Introduce a hrtimeout function

This patch adds a schedule_hrtimeout() function, to be used by select() and
poll() in a later patch. This function works similar to schedule_timeout()
in most ways, but takes a timespec rather than jiffies.

With a lot of contributions/fixes from Thomas

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 67 insertions, 0 deletions

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 6d93dce61cbb..becd17db1a1a 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -346,6 +346,8 @@ extern long hrtimer_nanosleep_restart(struct restart_block *restart_block);
 extern void hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
                                  struct task_struct *tsk);
 
+extern int schedule_hrtimeout(ktime_t *expires, const enum hrtimer_mode mode);
+
 /* Soft interrupt function to run the hrtimer queues: */
 extern void hrtimer_run_queues(void);
 extern void hrtimer_run_pending(void);
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index b8e4dce80a74..782137dc755f 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1678,3 +1678,68 @@ void __init hrtimers_init(void)
 #endif
 }
 
+/**
+ * schedule_hrtimeout - sleep until timeout
+ * @expires:    timeout value (ktime_t)
+ * @mode:       timer mode, HRTIMER_MODE_ABS or HRTIMER_MODE_REL
+ *
+ * Make the current task sleep until the given expiry time has
+ * elapsed. The routine will return immediately unless
+ * the current task state has been set (see set_current_state()).
+ *
+ * You can set the task state as follows -
+ *
+ * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
+ * pass before the routine returns.
+ *
+ * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
+ * delivered to the current task.
+ *
+ * The current task state is guaranteed to be TASK_RUNNING when this
+ * routine returns.
+ *
+ * Returns 0 when the timer has expired otherwise -EINTR
+ */
+int __sched schedule_hrtimeout(ktime_t *expires,
+                               const enum hrtimer_mode mode)
+{
+        struct hrtimer_sleeper t;
+
+        /*
+         * Optimize when a zero timeout value is given. It does not
+         * matter whether this is an absolute or a relative time.
+         */
+        if (expires && !expires->tv64) {
+                __set_current_state(TASK_RUNNING);
+                return 0;
+        }
+
+        /*
+         * A NULL parameter means "inifinte"
+         */
+        if (!expires) {
+                schedule();
+                __set_current_state(TASK_RUNNING);
+                return -EINTR;
+        }
+
+        hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC, mode);
+        t.timer.expires = *expires;
+
+        hrtimer_init_sleeper(&t, current);
+
+        hrtimer_start(&t.timer, t.timer.expires, mode);
+        if (!hrtimer_active(&t.timer))
+                t.task = NULL;
+
+        if (likely(t.task))
+                schedule();
+
+        hrtimer_cancel(&t.timer);
+        destroy_hrtimer_on_stack(&t.timer);
+
+        __set_current_state(TASK_RUNNING);
+
+        return !t.task ? 0 : -EINTR;
+}
+EXPORT_SYMBOL_GPL(schedule_hrtimeout);