[RFC][PATCH 1/2] timer: Convert timer_slack_ns from unsigned long to u64

[John Stultz]

The timer_slack_ns value in the task struct is currently a
unsigned long. This means that on 32bit applications, the
maximum slack is just over 4 seconds. However, on 64bit
machines, its much much larger (~500 years).

This disparity could make application development a little
difficult, so this patch extends the timer_slack_ns entry
(as well as the default_slack) to a u64. This means both 32bit
and 64bit systems have the same effective internal slack range.

Now the existing ABI via PR_GET_TIMERSLACK and PR_SET_TIMERSLACK
specify the interface as a unsigned long, so we preserve that
limitation on 32bit systems, where SET_TIMERSLACK can only set
the slack to a unsigned long value, and GET_TIMERSLACK will
return ULONG_MAX if the slack is actually larger then what can
be stored by an unsigned long.

This patch also modifies hrtimer functions which specified the
slack delta as a unsigned long.

Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Oren Laadan <orenl@xxxxxxxxxxx>
Cc: Ruchi Kandoi <kandoiruchi@xxxxxxxxxx>
Cc: Rom Lemarchand <romlem@xxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Android Kernel Team <kernel-team@xxxxxxxxxxx>
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
 fs/eventpoll.c          |  2 +-
 fs/select.c             |  8 ++++----
 include/linux/freezer.h |  2 +-
 include/linux/hrtimer.h | 12 +++++++-----
 include/linux/poll.h    |  2 +-
 include/linux/sched.h   |  4 ++--
 kernel/sys.c            |  5 ++++-
 kernel/time/hrtimer.c   |  8 ++++----
 kernel/time/timer.c     |  4 ++--
 9 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index ae1dbcf..344cd6d 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1596,7 +1596,7 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 {
 	int res = 0, eavail, timed_out = 0;
 	unsigned long flags;
-	long slack = 0;
+	u64 slack = 0;
 	wait_queue_t wait;
 	ktime_t expires, *to = NULL;
 
diff --git a/fs/select.c b/fs/select.c
index 79d0d49..8692939 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -70,9 +70,9 @@ static long __estimate_accuracy(struct timespec *tv)
 	return slack;
 }
 
-long select_estimate_accuracy(struct timespec *tv)
+u64 select_estimate_accuracy(struct timespec *tv)
 {
-	unsigned long ret;
+	u64 ret;
 	struct timespec now;
 
 	/*
@@ -402,7 +402,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 	struct poll_wqueues table;
 	poll_table *wait;
 	int retval, i, timed_out = 0;
-	unsigned long slack = 0;
+	u64 slack = 0;
 	unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 	unsigned long busy_end = 0;
 
@@ -784,7 +784,7 @@ static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
 	poll_table* pt = &wait->pt;
 	ktime_t expire, *to = NULL;
 	int timed_out = 0, count = 0;
-	unsigned long slack = 0;
+	u64 slack = 0;
 	unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 	unsigned long busy_end = 0;
 
diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index 6b7fd9c..dd03e83 100644
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -231,7 +231,7 @@ static inline long freezable_schedule_timeout_killable_unsafe(long timeout)
  * call this with locks held.
  */
 static inline int freezable_schedule_hrtimeout_range(ktime_t *expires,
-		unsigned long delta, const enum hrtimer_mode mode)
+		u64 delta, const enum hrtimer_mode mode)
 {
 	int __retval;
 	freezer_do_not_count();
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 2ead22d..c98c653 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -220,7 +220,7 @@ static inline void hrtimer_set_expires_range(struct hrtimer *timer, ktime_t time
 	timer->node.expires = ktime_add_safe(time, delta);
 }
 
-static inline void hrtimer_set_expires_range_ns(struct hrtimer *timer, ktime_t time, unsigned long delta)
+static inline void hrtimer_set_expires_range_ns(struct hrtimer *timer, ktime_t time, u64 delta)
 {
 	timer->_softexpires = time;
 	timer->node.expires = ktime_add_safe(time, ns_to_ktime(delta));
@@ -378,7 +378,7 @@ static inline void destroy_hrtimer_on_stack(struct hrtimer *timer) { }
 
 /* Basic timer operations: */
 extern void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
-			unsigned long range_ns, const enum hrtimer_mode mode);
+				   u64 range_ns, const enum hrtimer_mode mode);
 
 /**
  * hrtimer_start - (re)start an hrtimer on the current CPU
@@ -399,7 +399,7 @@ extern int hrtimer_try_to_cancel(struct hrtimer *timer);
 static inline void hrtimer_start_expires(struct hrtimer *timer,
 					 enum hrtimer_mode mode)
 {
-	unsigned long delta;
+	u64 delta;
 	ktime_t soft, hard;
 	soft = hrtimer_get_softexpires(timer);
 	hard = hrtimer_get_expires(timer);
@@ -477,10 +477,12 @@ 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_range(ktime_t *expires, unsigned long delta,
+extern int schedule_hrtimeout_range(ktime_t *expires, u64 delta,
 						const enum hrtimer_mode mode);
 extern int schedule_hrtimeout_range_clock(ktime_t *expires,
-		unsigned long delta, const enum hrtimer_mode mode, int clock);
+					  u64 delta,
+					  const enum hrtimer_mode mode,
+					  int clock);
 extern int schedule_hrtimeout(ktime_t *expires, const enum hrtimer_mode mode);
 
 /* Soft interrupt function to run the hrtimer queues: */
diff --git a/include/linux/poll.h b/include/linux/poll.h
index c08386f..9fb4f40 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -96,7 +96,7 @@ extern void poll_initwait(struct poll_wqueues *pwq);
 extern void poll_freewait(struct poll_wqueues *pwq);
 extern int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
 				 ktime_t *expires, unsigned long slack);
-extern long select_estimate_accuracy(struct timespec *tv);
+extern u64 select_estimate_accuracy(struct timespec *tv);
 
 
 static inline int poll_schedule(struct poll_wqueues *pwq, int state)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a10494a..1cc4a4f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1784,8 +1784,8 @@ struct task_struct {
 	 * 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;
+	u64 timer_slack_ns;
+	u64 default_timer_slack_ns;
 
 #ifdef CONFIG_KASAN
 	unsigned int kasan_depth;
diff --git a/kernel/sys.c b/kernel/sys.c
index 78947de..cf8ba54 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2169,7 +2169,10 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 		error = perf_event_task_enable();
 		break;
 	case PR_GET_TIMERSLACK:
-		error = current->timer_slack_ns;
+		if (current->timer_slack_ns > ULONG_MAX)
+			error = ULONG_MAX;
+		else
+			error = current->timer_slack_ns;
 		break;
 	case PR_SET_TIMERSLACK:
 		if (arg2 <= 0)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index fa909f9..58a321c 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -979,7 +979,7 @@ static inline ktime_t hrtimer_update_lowres(struct hrtimer *timer, ktime_t tim,
  *		relative (HRTIMER_MODE_REL)
  */
 void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
-			    unsigned long delta_ns, const enum hrtimer_mode mode)
+			    u64 delta_ns, const enum hrtimer_mode mode)
 {
 	struct hrtimer_clock_base *base, *new_base;
 	unsigned long flags;
@@ -1548,7 +1548,7 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
 	struct restart_block *restart;
 	struct hrtimer_sleeper t;
 	int ret = 0;
-	unsigned long slack;
+	u64 slack;
 
 	slack = current->timer_slack_ns;
 	if (dl_task(current) || rt_task(current))
@@ -1724,7 +1724,7 @@ void __init hrtimers_init(void)
  * @clock:	timer clock, CLOCK_MONOTONIC or CLOCK_REALTIME
  */
 int __sched
-schedule_hrtimeout_range_clock(ktime_t *expires, unsigned long delta,
+schedule_hrtimeout_range_clock(ktime_t *expires, u64 delta,
 			       const enum hrtimer_mode mode, int clock)
 {
 	struct hrtimer_sleeper t;
@@ -1792,7 +1792,7 @@ schedule_hrtimeout_range_clock(ktime_t *expires, unsigned long delta,
  *
  * Returns 0 when the timer has expired otherwise -EINTR
  */
-int __sched schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
+int __sched schedule_hrtimeout_range(ktime_t *expires, u64 delta,
 				     const enum hrtimer_mode mode)
 {
 	return schedule_hrtimeout_range_clock(expires, delta, mode,
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index bbc5d11..d1798fa 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1698,10 +1698,10 @@ EXPORT_SYMBOL(msleep_interruptible);
 static void __sched do_usleep_range(unsigned long min, unsigned long max)
 {
 	ktime_t kmin;
-	unsigned long delta;
+	u64 delta;
 
 	kmin = ktime_set(0, min * NSEC_PER_USEC);
-	delta = (max - min) * NSEC_PER_USEC;
+	delta = (u64)(max - min) * NSEC_PER_USEC;
 	schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
 }
 
-- 
1.9.1