[PATCH 17/31] ntsync: Allow waits to use the REALTIME clock.

[Elizabeth Figura]

NtWaitForMultipleObjects() can receive a timeout in two forms, relative or
absolute. Relative timeouts are unaffected by changes to the system time and do
not count down while the system suspends; for absolute timeouts the opposite is
true.

In order to make the interface and implementation simpler, the ntsync driver
only deals in absolute timeouts. However, we need to be able to emulate both
behaviours apropos suspension and time adjustment, which is achieved by allowing
either the MONOTONIC or REALTIME clock to be used.

Signed-off-by: Elizabeth Figura 
---
 drivers/misc/ntsync.c       | 9 ++++++++-
 include/uapi/linux/ntsync.h | 4 ++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
index 0773602cc86d..496704268603 100644
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c
@@ -765,11 +765,15 @@ static void put_obj(struct ntsync_obj *obj)
 static int ntsync_schedule(const struct ntsync_q *q, const struct ntsync_wait_args *args)
 {
    ktime_t timeout = ns_to_ktime(args->timeout);
+	clockid_t clock = CLOCK_MONOTONIC;
    ktime_t *timeout_ptr;
    int ret = 0;

timeout_ptr = (args->timeout == U64_MAX ? NULL : &timeout);

+	if (args->flags & NTSYNC_WAIT_REALTIME)
+		clock = CLOCK_REALTIME;
+
    do {
    	if (signal_pending(current)) {
    		ret = -ERESTARTSYS;
@@ -781,7 +785,7 @@ static int ntsync_schedule(const struct ntsync_q *q, const struct ntsync_wait_ar
    		ret = 0;
    		break;
    	}
-		ret = schedule_hrtimeout(timeout_ptr, HRTIMER_MODE_ABS);
+		ret = schedule_hrtimeout_range_clock(timeout_ptr, 0, HRTIMER_MODE_ABS, clock);
    } while (ret < 0);
    __set_current_state(TASK_RUNNING);

@@ -804,6 +808,9 @@ static int setup_wait(struct ntsync_device *dev,
    if (!args->owner)
    	return -EINVAL;

+	if (args->pad || (args->flags & ~NTSYNC_WAIT_REALTIME))
+		return -EINVAL;
+
    if (args->count > NTSYNC_MAX_WAIT_COUNT)
    	return -EINVAL;

diff --git a/include/uapi/linux/ntsync.h b/include/uapi/linux/ntsync.h
index 7c91af7011e4..074f26423426 100644
--- a/include/uapi/linux/ntsync.h
+++ b/include/uapi/linux/ntsync.h
@@ -28,6 +28,8 @@ struct ntsync_event_args {
    __u32 signaled;
 };

+#define NTSYNC_WAIT_REALTIME	0x1
+
 struct ntsync_wait_args {
    __u64 timeout;
    __u64 objs;
@@ -35,6 +37,8 @@ struct ntsync_wait_args {
    __u32 owner;
    __u32 index;
    __u32 alert;
+	__u32 flags;
+	__u32 pad;
 };

#define NTSYNC_MAX_WAIT_COUNT 64