alarmtimers/posixtimers: Bug fixes and spec conformity changes

index 5cb5b00..2b2e032 100644
@@ -387,7 +387,7 @@ void alarm_start_relative(struct alarm *alarm, ktime_t start)
 {
 	struct alarm_base *base = &alarm_bases[alarm->type];
 
-	start = ktime_add(start, base->gettime());
+	start = ktime_add_safe(start, base->gettime());
 	alarm_start(alarm, start);
 }
 EXPORT_SYMBOL_GPL(alarm_start_relative);

@@ -475,7 +475,7 @@ u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval)
 		overrun++;
 	}
 
-	alarm->node.expires = ktime_add(alarm->node.expires, interval);
+	alarm->node.expires = ktime_add_safe(alarm->node.expires, interval);
 	return overrun;
 }
 EXPORT_SYMBOL_GPL(alarm_forward);

@@ -666,7 +666,7 @@ static int alarm_timer_set(struct k_itimer *timr, int flags,
 		ktime_t now;
 
 		now = alarm_bases[timr->it.alarm.alarmtimer.type].gettime();
-		exp = ktime_add(now, exp);
+		exp = ktime_add_safe(now, exp);
 	}
 
 	alarm_start(&timr->it.alarm.alarmtimer, exp);

index 5cb5b00..2b2e032 100644
@@ -387,7 +387,7 @@ void alarm_start_relative(struct alarm *alarm, ktime_t start)
 {
 	struct alarm_base *base = &alarm_bases[alarm->type];
 
-	start = ktime_add(start, base->gettime());
+	start = ktime_add_safe(start, base->gettime());
 	alarm_start(alarm, start);
 }
 EXPORT_SYMBOL_GPL(alarm_start_relative);

@@ -475,7 +475,7 @@ u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval)
 		overrun++;
 	}
 
-	alarm->node.expires = ktime_add(alarm->node.expires, interval);
+	alarm->node.expires = ktime_add_safe(alarm->node.expires, interval);
 	return overrun;
 }
 EXPORT_SYMBOL_GPL(alarm_forward);

@@ -666,7 +666,7 @@ static int alarm_timer_set(struct k_itimer *timr, int flags,
 		ktime_t now;
 
 		now = alarm_bases[timr->it.alarm.alarmtimer.type].gettime();
-		exp = ktime_add(now, exp);
+		exp = ktime_add_safe(now, exp);
 	}
 
 	alarm_start(&timr->it.alarm.alarmtimer, exp);

index 2b2e032..ee2f420 100644
@@ -660,6 +660,14 @@ static int alarm_timer_set(struct k_itimer *timr, int flags,
 
 	/* start the timer */
 	timr->it.alarm.interval = timespec64_to_ktime(new_setting->it_interval);
+
+	/*
+	 * Rate limit to the tick as a hot fix to prevent DOS. Will be
+	 * mopped up later.
+	 */
+	if (timr->it.alarm.interval < TICK_NSEC)
+		timr->it.alarm.interval = TICK_NSEC;
+
 	exp = timespec64_to_ktime(new_setting->it_value);
 	/* Convert (if necessary) to absolute time */
 	if (flags != TIMER_ABSTIME) {

index 2b2e032..ee2f420 100644
@@ -660,6 +660,14 @@ static int alarm_timer_set(struct k_itimer *timr, int flags,
 
 	/* start the timer */
 	timr->it.alarm.interval = timespec64_to_ktime(new_setting->it_interval);
+
+	/*
+	 * Rate limit to the tick as a hot fix to prevent DOS. Will be
+	 * mopped up later.
+	 */
+	if (timr->it.alarm.interval < TICK_NSEC)
+		timr->it.alarm.interval = TICK_NSEC;
+
 	exp = timespec64_to_ktime(new_setting->it_value);
 	/* Convert (if necessary) to absolute time */
 	if (flags != TIMER_ABSTIME) {

index e645dcc..2a8675f 100644
@@ -520,8 +520,7 @@ static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm,
 
 	spin_lock_irqsave(&ptr->it_lock, flags);
 	if ((ptr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) {
-		if (IS_ENABLED(CONFIG_POSIX_TIMERS) &&
-		    posix_timer_event(ptr, 0) != 0)
+		if (posix_timer_event(ptr, 0))
 			ptr->it_overrun++;
 	}
 

index 0c0cccf..44d4865 100644
@@ -442,7 +442,6 @@ int posix_timer_event(struct k_itimer *timr, int si_private)
 	/* If we failed to send the signal the timer stops. */
 	return ret > 0;
 }
-EXPORT_SYMBOL_GPL(posix_timer_event);
 
 /*
  * This function gets called when a POSIX.1b interval timer expires.  It

index 83b22ae..38d8225 100644
@@ -42,12 +42,6 @@ struct posix_clock;
  * @clock_gettime:  Read the current time
  * @clock_getres:   Get the clock resolution
  * @clock_settime:  Set the current time value
- * @timer_create:   Create a new timer
- * @timer_delete:   Remove a previously created timer
- * @timer_gettime:  Get remaining time and interval of a timer
- * @timer_settime: Set a timer's initial expiration and interval
- * @fasync:         Optional character device fasync method
- * @mmap:           Optional character device mmap method
  * @open:           Optional character device open method
  * @release:        Optional character device release method
  * @ioctl:          Optional character device ioctl method

@@ -66,28 +60,12 @@ struct posix_clock_operations {
 	int  (*clock_settime)(struct posix_clock *pc,
 			      const struct timespec64 *ts);
 
-	int  (*timer_create) (struct posix_clock *pc, struct k_itimer *kit);
-
-	int  (*timer_delete) (struct posix_clock *pc, struct k_itimer *kit);
-
-	void (*timer_gettime)(struct posix_clock *pc,
-			      struct k_itimer *kit, struct itimerspec64 *tsp);
-
-	int  (*timer_settime)(struct posix_clock *pc,
-			      struct k_itimer *kit, int flags,
-			      struct itimerspec64 *tsp, struct itimerspec64 *old);
 	/*
 	 * Optional character device methods:
 	 */
-	int     (*fasync)  (struct posix_clock *pc,
-			    int fd, struct file *file, int on);
-
 	long    (*ioctl)   (struct posix_clock *pc,
 			    unsigned int cmd, unsigned long arg);
 
-	int     (*mmap)    (struct posix_clock *pc,
-			    struct vm_area_struct *vma);
-
 	int     (*open)    (struct posix_clock *pc, fmode_t f_mode);
 
 	uint    (*poll)    (struct posix_clock *pc,

134 lines not on this page · raw message

index 44d4865..b60b655 100644
@@ -69,6 +69,9 @@ static struct kmem_cache *posix_timers_cache;
 static DEFINE_HASHTABLE(posix_timers_hashtable, 9);
 static DEFINE_SPINLOCK(hash_lock);
 
+static const struct k_clock * const posix_clocks[];
+static const struct k_clock *clockid_to_kclock(const clockid_t id);
+
 /*
  * we assume that the new SIGEV_THREAD_ID shares no bits with the other
  * SIGEV values.  Here we put out an error if this assumption fails.

@@ -124,20 +127,6 @@ static DEFINE_SPINLOCK(hash_lock);
  *	    have is CLOCK_REALTIME and its high res counter part, both of
  *	    which we beg off on and pass to do_sys_settimeofday().
  */
-
-/*
- * These ones are defined below.
- */
-static int common_nsleep(const clockid_t, int flags, struct timespec64 *t,
-			 struct timespec __user *rmtp);
-static int common_timer_create(struct k_itimer *new_timer);
-static void common_timer_get(struct k_itimer *, struct itimerspec64 *);
-static int common_timer_set(struct k_itimer *, int,
-			    struct itimerspec64 *, struct itimerspec64 *);
-static int common_timer_del(struct k_itimer *timer);
-
-static enum hrtimer_restart posix_timer_fn(struct hrtimer *data);
-
 static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags);
 
 #define lock_timer(tid, flags)						   \

@@ -278,82 +267,6 @@ static int posix_get_hrtimer_res(clockid_t which_clock, struct timespec64 *tp)
 	return 0;
 }
 
-
-static const struct k_clock clock_realtime = {
-	.clock_getres	= posix_get_hrtimer_res,
-	.clock_get	= posix_clock_realtime_get,
-	.clock_set	= posix_clock_realtime_set,
-	.clock_adj	= posix_clock_realtime_adj,
-	.nsleep		= common_nsleep,
-	.nsleep_restart	= hrtimer_nanosleep_restart,
-	.timer_create	= common_timer_create,
-	.timer_set	= common_timer_set,
-	.timer_get	= common_timer_get,
-	.timer_del	= common_timer_del,
-};
-
-static const struct k_clock clock_monotonic = {
-	.clock_getres	= posix_get_hrtimer_res,
-	.clock_get	= posix_ktime_get_ts,
-	.nsleep		= common_nsleep,
-	.nsleep_restart	= hrtimer_nanosleep_restart,
-	.timer_create	= common_timer_create,
-	.timer_set	= common_timer_set,
-	.timer_get	= common_timer_get,
-	.timer_del	= common_timer_del,
-};
-
-static const struct k_clock clock_monotonic_raw = {
-	.clock_getres	= posix_get_hrtimer_res,
-	.clock_get	= posix_get_monotonic_raw,
-};
-
-static const struct k_clock clock_realtime_coarse = {
-	.clock_getres	= posix_get_coarse_res,
-	.clock_get	= posix_get_realtime_coarse,
-};
-
-static const struct k_clock clock_monotonic_coarse = {
-	.clock_getres	= posix_get_coarse_res,
-	.clock_get	= posix_get_monotonic_coarse,
-};
-
-static const struct k_clock clock_tai = {
-	.clock_getres	= posix_get_hrtimer_res,
-	.clock_get	= posix_get_tai,
-	.nsleep		= common_nsleep,
-	.nsleep_restart	= hrtimer_nanosleep_restart,
-	.timer_create	= common_timer_create,
-	.timer_set	= common_timer_set,
-	.timer_get	= common_timer_get,
-	.timer_del	= common_timer_del,
-};
-
-static const struct k_clock clock_boottime = {
-	.clock_getres	= posix_get_hrtimer_res,
-	.clock_get	= posix_get_boottime,
-	.nsleep		= common_nsleep,
-	.nsleep_restart	= hrtimer_nanosleep_restart,
-	.timer_create	= common_timer_create,
-	.timer_set	= common_timer_set,
-	.timer_get	= common_timer_get,
-	.timer_del	= common_timer_del,
-};
-
-static const struct k_clock * const posix_clocks[] = {
-	[CLOCK_REALTIME]		= &clock_realtime,
-	[CLOCK_MONOTONIC]		= &clock_monotonic,
-	[CLOCK_PROCESS_CPUTIME_ID]	= &clock_process,
-	[CLOCK_THREAD_CPUTIME_ID]	= &clock_thread,
-	[CLOCK_MONOTONIC_RAW]		= &clock_monotonic_raw,
-	[CLOCK_REALTIME_COARSE]		= &clock_realtime_coarse,
-	[CLOCK_MONOTONIC_COARSE]	= &clock_monotonic_coarse,
-	[CLOCK_BOOTTIME]		= &clock_boottime,
-	[CLOCK_REALTIME_ALARM]		= &alarm_clock,
-	[CLOCK_BOOTTIME_ALARM]		= &alarm_clock,
-	[CLOCK_TAI]			= &clock_tai,
-};
-
 /*
  * Initialize everything, well, just everything in Posix clocks/timers ;)
  */

@@ -567,17 +480,6 @@ static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
 	call_rcu(&tmr->it.rcu, k_itimer_rcu_free);
 }
 
-static const struct k_clock *clockid_to_kclock(const clockid_t id)
-{
-	if (id < 0)
-		return (id & CLOCKFD_MASK) == CLOCKFD ?
-			&clock_posix_dynamic : &clock_posix_cpu;
-
-	if (id >= ARRAY_SIZE(posix_clocks) || !posix_clocks[id])
-		return NULL;
-	return posix_clocks[id];
-}
-
 static int common_timer_create(struct k_itimer *new_timer)
 {
 	hrtimer_init(&new_timer->it.real.timer, new_timer->it_clock, 0);

@@ -1129,3 +1031,89 @@ long clock_nanosleep_restart(struct restart_block *restart_block)
 
 	return kc->nsleep_restart(restart_block);
 }
+
+static const struct k_clock clock_realtime = {
+	.clock_getres	= posix_get_hrtimer_res,
+	.clock_get	= posix_clock_realtime_get,
+	.clock_set	= posix_clock_realtime_set,
+	.clock_adj	= posix_clock_realtime_adj,
+	.nsleep		= common_nsleep,
+	.nsleep_restart	= hrtimer_nanosleep_restart,
+	.timer_create	= common_timer_create,
+	.timer_set	= common_timer_set,
+	.timer_get	= common_timer_get,
+	.timer_del	= common_timer_del,
+};
+
+static const struct k_clock clock_monotonic = {
+	.clock_getres	= posix_get_hrtimer_res,
+	.clock_get	= posix_ktime_get_ts,
+	.nsleep		= common_nsleep,
+	.nsleep_restart	= hrtimer_nanosleep_restart,
+	.timer_create	= common_timer_create,
+	.timer_set	= common_timer_set,
+	.timer_get	= common_timer_get,
+	.timer_del	= common_timer_del,
+};
+
+static const struct k_clock clock_monotonic_raw = {
+	.clock_getres	= posix_get_hrtimer_res,
+	.clock_get	= posix_get_monotonic_raw,
+};
+
+static const struct k_clock clock_realtime_coarse = {
+	.clock_getres	= posix_get_coarse_res,
+	.clock_get	= posix_get_realtime_coarse,
+};
+
+static const struct k_clock clock_monotonic_coarse = {
+	.clock_getres	= posix_get_coarse_res,
+	.clock_get	= posix_get_monotonic_coarse,
+};
+
+static const struct k_clock clock_tai = {
+	.clock_getres	= posix_get_hrtimer_res,
+	.clock_get	= posix_get_tai,
+	.nsleep		= common_nsleep,
+	.nsleep_restart	= hrtimer_nanosleep_restart,
+	.timer_create	= common_timer_create,
+	.timer_set	= common_timer_set,
+	.timer_get	= common_timer_get,
+	.timer_del	= common_timer_del,
+};
+
+static const struct k_clock clock_boottime = {
+	.clock_getres	= posix_get_hrtimer_res,
+	.clock_get	= posix_get_boottime,
+	.nsleep		= common_nsleep,
+	.nsleep_restart	= hrtimer_nanosleep_restart,
+	.timer_create	= common_timer_create,
+	.timer_set	= common_timer_set,
+	.timer_get	= common_timer_get,
+	.timer_del	= common_timer_del,
+};
+
+static const struct k_clock * const posix_clocks[] = {
+	[CLOCK_REALTIME]		= &clock_realtime,
+	[CLOCK_MONOTONIC]		= &clock_monotonic,
+	[CLOCK_PROCESS_CPUTIME_ID]	= &clock_process,
+	[CLOCK_THREAD_CPUTIME_ID]	= &clock_thread,
+	[CLOCK_MONOTONIC_RAW]		= &clock_monotonic_raw,
+	[CLOCK_REALTIME_COARSE]		= &clock_realtime_coarse,
+	[CLOCK_MONOTONIC_COARSE]	= &clock_monotonic_coarse,
+	[CLOCK_BOOTTIME]		= &clock_boottime,
+	[CLOCK_REALTIME_ALARM]		= &alarm_clock,
+	[CLOCK_BOOTTIME_ALARM]		= &alarm_clock,
+	[CLOCK_TAI]			= &clock_tai,
+};
+
+static const struct k_clock *clockid_to_kclock(const clockid_t id)
+{
+	if (id < 0)
+		return (id & CLOCKFD_MASK) == CLOCKFD ?
+			&clock_posix_dynamic : &clock_posix_cpu;
+
+	if (id >= ARRAY_SIZE(posix_clocks) || !posix_clocks[id])
+		return NULL;
+	return posix_clocks[id];
+}

index 8929f7e..e06062c 100644
@@ -49,35 +49,54 @@ struct cpu_timer_list {
 #define FD_TO_CLOCKID(fd)	((~(clockid_t) (fd) << 3) | CLOCKFD)
 #define CLOCKID_TO_FD(clk)	((unsigned int) ~((clk) >> 3))
 
-/* POSIX.1b interval timer structure. */
-struct k_itimer {
-	struct list_head list;		/* free/ allocate list */
-	struct hlist_node t_hash;
-	spinlock_t it_lock;
-	clockid_t it_clock;		/* which timer type */
-	timer_t it_id;			/* timer id */
-	int it_overrun;			/* overrun on pending signal  */
-	int it_overrun_last;		/* overrun on last delivered signal */
-	int it_requeue_pending;		/* waiting to requeue this timer */
 #define REQUEUE_PENDING 1
-	int it_sigev_notify;		/* notify word of sigevent struct */
-	struct signal_struct *it_signal;
+
+/**
+ * struct k_itimer - POSIX.1b interval timer structure.
+ * @list:		List head for binding the timer to signals->posix_timers
+ * @t_hash:		Entry in the posix timer hash table
+ * @it_lock:		Lock protecting the timer
+ * @it_clock:		The posix timer clock id
+ * @it_id:		The posix timer id for identifying the timer
+ * @it_overrun:		The overrun counter for pending signals
+ * @it_overrun_last:	The overrun at the time of the last delivered signal
+ * @it_requeue_pending:	Indicator that timer waits for being requeued on
+ *			signal delivery
+ * @it_sigev_notify:	The notify word of sigevent struct for signal delivery
+ * @it_signal:		Pointer to the creators signal struct
+ * @it_pid:		The pid of the process/task targeted by the signal
+ * @it_process:		The task to wakeup on clock_nanosleep (CPU timers)
+ * @sigq:		Pointer to preallocated sigqueue
+ * @it:			Union representing the various posix timer type
+ *			internals. Also used for rcu freeing the timer.
+ */
+struct k_itimer {
+	struct list_head	list;
+	struct hlist_node	t_hash;
+	spinlock_t		it_lock;
+	clockid_t		it_clock;
+	timer_t			it_id;
+	int			it_overrun;
+	int			it_overrun_last;
+	int			it_requeue_pending;
+	int			it_sigev_notify;
+	struct signal_struct	*it_signal;
 	union {
-		struct pid *it_pid;	/* pid of process to send signal to */
-		struct task_struct *it_process;	/* for clock_nanosleep */
+		struct pid		*it_pid;
+		struct task_struct	*it_process;
 	};
-	struct sigqueue *sigq;		/* signal queue entry. */
+	struct sigqueue		*sigq;
 	union {
 		struct {
-			struct hrtimer timer;
-			ktime_t interval;
+			struct hrtimer	timer;
+			ktime_t		interval;
 		} real;
-		struct cpu_timer_list cpu;
+		struct cpu_timer_list	cpu;
 		struct {
-			struct alarm alarmtimer;
-			ktime_t interval;
+			struct alarm	alarmtimer;
+			ktime_t		interval;
 		} alarm;
-		struct rcu_head rcu;
+		struct rcu_head		rcu;
 	} it;
 };
 

index e06062c..a372e7e 100644
@@ -100,36 +100,6 @@ struct k_itimer {
 	} it;
 };
 
-struct k_clock {
-	int (*clock_getres) (const clockid_t which_clock, struct timespec64 *tp);
-	int (*clock_set) (const clockid_t which_clock,
-			  const struct timespec64 *tp);
-	int (*clock_get) (const clockid_t which_clock, struct timespec64 *tp);
-	int (*clock_adj) (const clockid_t which_clock, struct timex *tx);
-	int (*timer_create) (struct k_itimer *timer);
-	int (*nsleep) (const clockid_t which_clock, int flags,
-		       struct timespec64 *, struct timespec __user *);
-	long (*nsleep_restart) (struct restart_block *restart_block);
-	int (*timer_set) (struct k_itimer *timr, int flags,
-			  struct itimerspec64 *new_setting,
-			  struct itimerspec64 *old_setting);
-	int (*timer_del) (struct k_itimer *timr);
-#define TIMER_RETRY 1
-	void (*timer_get) (struct k_itimer *timr,
-			   struct itimerspec64 *cur_setting);
-};
-
-extern const struct k_clock clock_posix_cpu;
-extern const struct k_clock clock_posix_dynamic;
-extern const struct k_clock clock_process;
-extern const struct k_clock clock_thread;
-extern const struct k_clock alarm_clock;
-
-/* function to call to trigger timer event */
-int posix_timer_event(struct k_itimer *timr, int si_private);
-
-void posix_cpu_timer_schedule(struct k_itimer *timer);
-
 void run_posix_cpu_timers(struct task_struct *task);
 void posix_cpu_timers_exit(struct task_struct *task);
 void posix_cpu_timers_exit_group(struct task_struct *task);

index 2a8675f..36855d6 100644
@@ -28,6 +28,8 @@
 #include <linux/workqueue.h>
 #include <linux/freezer.h>
 
+#include "posix-timers.h"
+
 #define CREATE_TRACE_POINTS
 #include <trace/events/alarmtimer.h>
 

index bd4fb78..17cdc55 100644
@@ -25,6 +25,8 @@
 #include <linux/syscalls.h>
 #include <linux/uaccess.h>
 
+#include "posix-timers.h"
+
 static void delete_clock(struct kref *kref);
 
 /*

index c994347..a77a792 100644
@@ -13,6 +13,8 @@
 #include <linux/tick.h>
 #include <linux/workqueue.h>
 
+#include "posix-timers.h"
+
 /*
  * Called after updating RLIMIT_CPU to run cpu timer and update
  * tsk->signal->cputime_expires expiration cache if necessary. Needs

index b60b655..dee6a0d 100644
@@ -51,6 +51,7 @@
 #include <linux/hashtable.h>
 
 #include "timekeeping.h"
+#include "posix-timers.h"
 
 /*
  * Management arrays for POSIX timers. Timers are now kept in static hash table

new file mode 100644
index 0000000..ad2dbd2
@@ -0,0 +1,29 @@
+#define TIMER_RETRY 1
+
+struct k_clock {
+	int (*clock_getres) (const clockid_t which_clock, struct timespec64 *tp);
+	int (*clock_set) (const clockid_t which_clock,
+			  const struct timespec64 *tp);
+	int (*clock_get) (const clockid_t which_clock, struct timespec64 *tp);
+	int (*clock_adj) (const clockid_t which_clock, struct timex *tx);
+	int (*timer_create) (struct k_itimer *timer);
+	int (*nsleep) (const clockid_t which_clock, int flags,
+		       struct timespec64 *, struct timespec __user *);
+	long (*nsleep_restart) (struct restart_block *restart_block);
+	int (*timer_set) (struct k_itimer *timr, int flags,
+			  struct itimerspec64 *new_setting,
+			  struct itimerspec64 *old_setting);
+	int (*timer_del) (struct k_itimer *timr);
+	void (*timer_get) (struct k_itimer *timr,
+			   struct itimerspec64 *cur_setting);
+};
+
+extern const struct k_clock clock_posix_cpu;
+extern const struct k_clock clock_posix_dynamic;
+extern const struct k_clock clock_process;
+extern const struct k_clock clock_thread;
+extern const struct k_clock alarm_clock;
+
+int posix_timer_event(struct k_itimer *timr, int si_private);
+
+void posix_cpu_timer_schedule(struct k_itimer *timer);

index a77a792..1683e50 100644
@@ -527,6 +527,7 @@ static void cpu_timer_fire(struct k_itimer *timer)
 		 * ticking in case the signal is deliverable next time.
 		 */
 		posix_cpu_timer_schedule(timer);
+		++timer->it_requeue_pending;
 	}
 }
 

@@ -997,12 +998,12 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
 		cpu_clock_sample(timer->it_clock, p, &now);
 		bump_cpu_timer(timer, now);
 		if (unlikely(p->exit_state))
-			goto out;
+			return;
 
 		/* Protect timer list r/w in arm_timer() */
 		sighand = lock_task_sighand(p, &flags);
 		if (!sighand)
-			goto out;
+			return;
 	} else {
 		/*
 		 * Protect arm_timer() and timer sampling in case of call to

@@ -1015,11 +1016,10 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
 			 * We can't even collect a sample any more.
 			 */
 			timer->it.cpu.expires = 0;
-			goto out;
+			return;
 		} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
-			unlock_task_sighand(p, &flags);
-			/* Optimizations: if the process is dying, no need to rearm */
-			goto out;
+			/* If the process is dying, no need to rearm */
+			goto unlock;
 		}
 		cpu_timer_sample_group(timer->it_clock, p, &now);
 		bump_cpu_timer(timer, now);

@@ -1031,12 +1031,8 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
 	 */
 	WARN_ON_ONCE(!irqs_disabled());
 	arm_timer(timer);
+unlock:
 	unlock_task_sighand(p, &flags);
-
-out:
-	timer->it_overrun_last = timer->it_overrun;
-	timer->it_overrun = -1;
-	++timer->it_requeue_pending;
 }
 
 /**

index dee6a0d..79a00e0 100644
@@ -291,10 +291,6 @@ static void schedule_next_timer(struct k_itimer *timr)
 	timr->it_overrun += (unsigned int) hrtimer_forward(timer,
 						timer->base->get_time(),
 						timr->it.real.interval);
-
-	timr->it_overrun_last = timr->it_overrun;
-	timr->it_overrun = -1;
-	++timr->it_requeue_pending;
 	hrtimer_restart(timer);
 }
 

@@ -315,18 +311,23 @@ void do_schedule_next_timer(struct siginfo *info)
 	unsigned long flags;
 
 	timr = lock_timer(info->si_tid, &flags);
+	if (!timr)
+		return;
 
-	if (timr && timr->it_requeue_pending == info->si_sys_private) {
+	if (timr->it_requeue_pending == info->si_sys_private) {
 		if (timr->it_clock < 0)
 			posix_cpu_timer_schedule(timr);
 		else
 			schedule_next_timer(timr);
 
+		timr->it_overrun_last = timr->it_overrun;
+		timr->it_overrun = -1;
+		++timr->it_requeue_pending;
+
 		info->si_overrun += timr->it_overrun_last;
 	}
 
-	if (timr)
-		unlock_timer(timr, flags);
+	unlock_timer(timr, flags);
 }
 
 int posix_timer_event(struct k_itimer *timr, int si_private)

index a372e7e..908048f 100644
@@ -63,6 +63,7 @@ struct cpu_timer_list {
  * @it_requeue_pending:	Indicator that timer waits for being requeued on
  *			signal delivery
  * @it_sigev_notify:	The notify word of sigevent struct for signal delivery
+ * @it_interval:	The interval for periodic timers
  * @it_signal:		Pointer to the creators signal struct
  * @it_pid:		The pid of the process/task targeted by the signal
  * @it_process:		The task to wakeup on clock_nanosleep (CPU timers)

@@ -80,6 +81,7 @@ struct k_itimer {
 	int			it_overrun_last;
 	int			it_requeue_pending;
 	int			it_sigev_notify;
+	ktime_t			it_interval;
 	struct signal_struct	*it_signal;
 	union {
 		struct pid		*it_pid;

@@ -89,12 +91,10 @@ struct k_itimer {
 	union {
 		struct {
 			struct hrtimer	timer;
-			ktime_t		interval;
 		} real;
 		struct cpu_timer_list	cpu;
 		struct {
 			struct alarm	alarmtimer;
-			ktime_t		interval;
 		} alarm;
 		struct rcu_head		rcu;
 	} it;

index 36855d6..5b8cf4b 100644
@@ -527,9 +527,8 @@ static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm,
 	}
 
 	/* Re-add periodic timers */
-	if (ptr->it.alarm.interval) {
-		ptr->it_overrun += alarm_forward(alarm, now,
-						ptr->it.alarm.interval);
+	if (ptr->it_interval) {
+		ptr->it_overrun += alarm_forward(alarm, now, ptr->it_interval);
 		result = ALARMTIMER_RESTART;
 	}
 	spin_unlock_irqrestore(&ptr->it_lock, flags);

@@ -613,7 +612,7 @@ static void alarm_timer_get(struct k_itimer *timr,
 		cur_setting->it_value.tv_nsec = 0;
 	}
 
-	cur_setting->it_interval = ktime_to_timespec64(timr->it.alarm.interval);
+	cur_setting->it_interval = ktime_to_timespec64(timr->it_interval);
 }
 
 /**

@@ -662,14 +661,14 @@ static int alarm_timer_set(struct k_itimer *timr, int flags,
 		return TIMER_RETRY;
 
 	/* start the timer */
-	timr->it.alarm.interval = timespec64_to_ktime(new_setting->it_interval);
+	timr->it_interval = timespec64_to_ktime(new_setting->it_interval);
 
 	/*
 	 * Rate limit to the tick as a hot fix to prevent DOS. Will be
 	 * mopped up later.
 	 */
-	if (timr->it.alarm.interval < TICK_NSEC)
-		timr->it.alarm.interval = TICK_NSEC;
+	if (timr->it_interval < TICK_NSEC)
+		timr->it_interval = TICK_NSEC;
 
 	exp = timespec64_to_ktime(new_setting->it_value);
 	/* Convert (if necessary) to absolute time */

index 79a00e0..7dd992c 100644
@@ -285,12 +285,12 @@ static void schedule_next_timer(struct k_itimer *timr)
 {
 	struct hrtimer *timer = &timr->it.real.timer;
 
-	if (timr->it.real.interval == 0)
+	if (!timr->it_interval)
 		return;
 
 	timr->it_overrun += (unsigned int) hrtimer_forward(timer,
 						timer->base->get_time(),
-						timr->it.real.interval);
+						timr->it_interval);
 	hrtimer_restart(timer);
 }
 

@@ -375,7 +375,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
 	timr = container_of(timer, struct k_itimer, it.real.timer);
 	spin_lock_irqsave(&timr->it_lock, flags);
 
-	if (timr->it.real.interval != 0)
+	if (timr->it_interval != 0)
 		si_private = ++timr->it_requeue_pending;
 
 	if (posix_timer_event(timr, si_private)) {

@@ -384,7 +384,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
 		 * we will not get a call back to restart it AND
 		 * it should be restarted.
 		 */
-		if (timr->it.real.interval != 0) {
+		if (timr->it_interval != 0) {
 			ktime_t now = hrtimer_cb_get_time(timer);
 
 			/*

@@ -413,13 +413,13 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
 			{
 				ktime_t kj = NSEC_PER_SEC / HZ;
 
-				if (timr->it.real.interval < kj)
+				if (timr->it_interval < kj)
 					now = ktime_add(now, kj);
 			}
 #endif
 			timr->it_overrun += (unsigned int)
 				hrtimer_forward(timer, now,
-						timr->it.real.interval);
+						timr->it_interval);
 			ret = HRTIMER_RESTART;
 			++timr->it_requeue_pending;
 		}

@@ -631,7 +631,7 @@ common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting)
 
 	memset(cur_setting, 0, sizeof(*cur_setting));
 
-	iv = timr->it.real.interval;
+	iv = timr->it_interval;
 
 	/* interval timer ? */
 	if (iv)

@@ -732,7 +732,7 @@ common_timer_set(struct k_itimer *timr, int flags,
 		common_timer_get(timr, old_setting);
 
 	/* disable the timer */
-	timr->it.real.interval = 0;
+	timr->it_interval = 0;
 	/*
 	 * careful here.  If smp we could be in the "fire" routine which will
 	 * be spinning as we hold the lock.  But this is ONLY an SMP issue.

@@ -755,7 +755,7 @@ common_timer_set(struct k_itimer *timr, int flags,
 	hrtimer_set_expires(timer, timespec64_to_ktime(new_setting->it_value));
 
 	/* Convert interval */
-	timr->it.real.interval = timespec64_to_ktime(new_setting->it_interval);
+	timr->it_interval = timespec64_to_ktime(new_setting->it_interval);
 
 	/* SIGEV_NONE timers are not queued ! See common_timer_get */
 	if (((timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE)) {

@@ -820,7 +820,7 @@ retry:
 
 static int common_timer_del(struct k_itimer *timer)
 {
-	timer->it.real.interval = 0;
+	timer->it_interval = 0;
 
 	if (hrtimer_try_to_cancel(&timer->it.real.timer) < 0)
 		return TIMER_RETRY;

index 908048f..8f9cca3 100644
@@ -56,6 +56,7 @@ struct cpu_timer_list {
  * @list:		List head for binding the timer to signals->posix_timers
  * @t_hash:		Entry in the posix timer hash table
  * @it_lock:		Lock protecting the timer
+ * @kclock:		Pointer to the k_clock struct handling this timer
  * @it_clock:		The posix timer clock id
  * @it_id:		The posix timer id for identifying the timer
  * @it_overrun:		The overrun counter for pending signals

@@ -75,6 +76,7 @@ struct k_itimer {
 	struct list_head	list;
 	struct hlist_node	t_hash;
 	spinlock_t		it_lock;
+	const struct k_clock	*kclock;
 	clockid_t		it_clock;
 	timer_t			it_id;
 	int			it_overrun;

index 1683e50..0123ece 100644
@@ -324,6 +324,8 @@ static int posix_cpu_timer_create(struct k_itimer *new_timer)
 	if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 		return -EINVAL;
 
+	new_timer->kclock = &clock_posix_cpu;
+
 	INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 
 	rcu_read_lock();

index 7dd992c..eb007e1 100644
@@ -519,6 +519,7 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
 	it_id_set = IT_ID_SET;
 	new_timer->it_id = (timer_t) new_timer_id;
 	new_timer->it_clock = which_clock;
+	new_timer->kclock = kc;
 	new_timer->it_overrun = -1;
 
 	if (timer_event_spec) {

@@ -679,7 +680,7 @@ SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
 	if (!timr)
 		return -EINVAL;
 
-	kc = clockid_to_kclock(timr->it_clock);
+	kc = timr->kclock;
 	if (WARN_ON_ONCE(!kc || !kc->timer_get))
 		ret = -EINVAL;
 	else

@@ -798,7 +799,7 @@ retry:
 	if (!timr)
 		return -EINVAL;
 
-	kc = clockid_to_kclock(timr->it_clock);
+	kc = timr->kclock;
 	if (WARN_ON_ONCE(!kc || !kc->timer_set))
 		error = -EINVAL;
 	else

@@ -829,7 +830,7 @@ static int common_timer_del(struct k_itimer *timer)
 
 static inline int timer_delete_hook(struct k_itimer *timer)
 {
-	const struct k_clock *kc = clockid_to_kclock(timer->it_clock);
+	const struct k_clock *kc = timer->kclock;
 
 	if (WARN_ON_ONCE(!kc || !kc->timer_del))
 		return -EINVAL;

index ad2dbd2..02ffd1b 100644
@@ -1,21 +1,24 @@
 #define TIMER_RETRY 1
 
 struct k_clock {
-	int (*clock_getres) (const clockid_t which_clock, struct timespec64 *tp);
-	int (*clock_set) (const clockid_t which_clock,
-			  const struct timespec64 *tp);
-	int (*clock_get) (const clockid_t which_clock, struct timespec64 *tp);
-	int (*clock_adj) (const clockid_t which_clock, struct timex *tx);
-	int (*timer_create) (struct k_itimer *timer);
-	int (*nsleep) (const clockid_t which_clock, int flags,
-		       struct timespec64 *, struct timespec __user *);
-	long (*nsleep_restart) (struct restart_block *restart_block);
-	int (*timer_set) (struct k_itimer *timr, int flags,
-			  struct itimerspec64 *new_setting,
-			  struct itimerspec64 *old_setting);
-	int (*timer_del) (struct k_itimer *timr);
-	void (*timer_get) (struct k_itimer *timr,
-			   struct itimerspec64 *cur_setting);
+	int	(*clock_getres)(const clockid_t which_clock,
+				struct timespec64 *tp);
+	int	(*clock_set)(const clockid_t which_clock,
+			     const struct timespec64 *tp);
+	int	(*clock_get)(const clockid_t which_clock,
+			     struct timespec64 *tp);
+	int	(*clock_adj)(const clockid_t which_clock, struct timex *tx);
+	int	(*timer_create)(struct k_itimer *timer);
+	int	(*nsleep)(const clockid_t which_clock, int flags,
+			  struct timespec64 *, struct timespec __user *);
+	long	(*nsleep_restart)(struct restart_block *restart_block);
+	int	(*timer_set)(struct k_itimer *timr, int flags,
+			     struct itimerspec64 *new_setting,
+			     struct itimerspec64 *old_setting);
+	int	(*timer_del)(struct k_itimer *timr);
+	void	(*timer_get)(struct k_itimer *timr,
+			     struct itimerspec64 *cur_setting);
+	void	(*timer_rearm)(struct k_itimer *timr);
 };
 
 extern const struct k_clock clock_posix_cpu;

index 8f9cca3..771e5f7 100644
@@ -112,6 +112,6 @@ long clock_nanosleep_restart(struct restart_block *restart_block);
 
 void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new);
 
-void do_schedule_next_timer(struct siginfo *info);
+void posixtimer_rearm(struct siginfo *info);
 
 #endif

index 1f85c84..d031cd2 100644
@@ -630,7 +630,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
 		 * about to disable them again anyway.
 		 */
 		spin_unlock(&tsk->sighand->siglock);
-		do_schedule_next_timer(info);
+		posixtimer_rearm(info);
 		spin_lock(&tsk->sighand->siglock);
 	}
 #endif

index 0123ece..1ba576d 100644
@@ -981,7 +981,7 @@ static void check_process_timers(struct task_struct *tsk,
 }
 
 /*
- * This is called from the signal code (via do_schedule_next_timer)
+ * This is called from the signal code (via posixtimer_rearm)
  * when the last timer signal was delivered and we have to reload the timer.
  */
 void posix_cpu_timer_schedule(struct k_itimer *timer)

index eb007e1..036b7e7 100644
@@ -305,7 +305,7 @@ static void schedule_next_timer(struct k_itimer *timr)
  * To protect against the timer going away while the interrupt is queued,
  * we require that the it_requeue_pending flag be set.
  */
-void do_schedule_next_timer(struct siginfo *info)
+void posixtimer_rearm(struct siginfo *info)
 {
 	struct k_itimer *timr;
 	unsigned long flags;

@@ -336,12 +336,12 @@ int posix_timer_event(struct k_itimer *timr, int si_private)
 	int shared, ret = -1;
 	/*
 	 * FIXME: if ->sigq is queued we can race with
-	 * dequeue_signal()->do_schedule_next_timer().
+	 * dequeue_signal()->posixtimer_rearm().
 	 *
 	 * If dequeue_signal() sees the "right" value of
-	 * si_sys_private it calls do_schedule_next_timer().
+	 * si_sys_private it calls posixtimer_rearm().
 	 * We re-queue ->sigq and drop ->it_lock().
-	 * do_schedule_next_timer() locks the timer
+	 * posixtimer_rearm() locks the timer
 	 * and re-schedules it while ->sigq is pending.
 	 * Not really bad, but not that we want.
 	 */

@@ -701,7 +701,7 @@ SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
  * accumulating overruns on the next timer.  The overrun is frozen when
  * the signal is delivered, either at the notify time (if the info block
  * is not queued) or at the actual delivery time (as we are informed by
- * the call back to do_schedule_next_timer().  So all we need to do is
+ * the call back to posixtimer_rearm().  So all we need to do is
  * to pick up the frozen overrun.
  */
 SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id)

index 1ba576d..96c833a 100644
@@ -15,6 +15,8 @@
 
 #include "posix-timers.h"
 
+static void posix_cpu_timer_rearm(struct k_itimer *timer);
+
 /*
  * Called after updating RLIMIT_CPU to run cpu timer and update
  * tsk->signal->cputime_expires expiration cache if necessary. Needs

@@ -528,7 +530,7 @@ static void cpu_timer_fire(struct k_itimer *timer)
 		 * reload the timer.  But we need to keep it
 		 * ticking in case the signal is deliverable next time.
 		 */
-		posix_cpu_timer_schedule(timer);
+		posix_cpu_timer_rearm(timer);
 		++timer->it_requeue_pending;
 	}
 }

@@ -984,7 +986,7 @@ static void check_process_timers(struct task_struct *tsk,
  * This is called from the signal code (via posixtimer_rearm)
  * when the last timer signal was delivered and we have to reload the timer.
  */
-void posix_cpu_timer_schedule(struct k_itimer *timer)
+static void posix_cpu_timer_rearm(struct k_itimer *timer)
 {
 	struct sighand_struct *sighand;
 	unsigned long flags;

@@ -1431,6 +1433,7 @@ const struct k_clock clock_posix_cpu = {
 	.timer_set	= posix_cpu_timer_set,
 	.timer_del	= posix_cpu_timer_del,
 	.timer_get	= posix_cpu_timer_get,
+	.timer_rearm	= posix_cpu_timer_rearm,
 };
 
 const struct k_clock clock_process = {

index 036b7e7..b12582a 100644
@@ -278,10 +278,9 @@ static __init int init_posix_timers(void)
 					NULL);
 	return 0;
 }
-
 __initcall(init_posix_timers);
 
-static void schedule_next_timer(struct k_itimer *timr)
+static void common_hrtimer_rearm(struct k_itimer *timr)
 {
 	struct hrtimer *timer = &timr->it.real.timer;
 

@@ -315,10 +314,7 @@ void posixtimer_rearm(struct siginfo *info)
 		return;
 
 	if (timr->it_requeue_pending == info->si_sys_private) {
-		if (timr->it_clock < 0)
-			posix_cpu_timer_schedule(timr);
-		else
-			schedule_next_timer(timr);
+		timr->kclock->timer_rearm(timr);
 
 		timr->it_overrun_last = timr->it_overrun;
 		timr->it_overrun = -1;

@@ -1046,6 +1042,7 @@ static const struct k_clock clock_realtime = {
 	.timer_set	= common_timer_set,
 	.timer_get	= common_timer_get,
 	.timer_del	= common_timer_del,
+	.timer_rearm	= common_hrtimer_rearm,
 };
 
 static const struct k_clock clock_monotonic = {

@@ -1057,6 +1054,7 @@ static const struct k_clock clock_monotonic = {
 	.timer_set	= common_timer_set,
 	.timer_get	= common_timer_get,
 	.timer_del	= common_timer_del,
+	.timer_rearm	= common_hrtimer_rearm,
 };
 
 static const struct k_clock clock_monotonic_raw = {

@@ -1083,6 +1081,7 @@ static const struct k_clock clock_tai = {
 	.timer_set	= common_timer_set,
 	.timer_get	= common_timer_get,
 	.timer_del	= common_timer_del,
+	.timer_rearm	= common_hrtimer_rearm,
 };
 
 static const struct k_clock clock_boottime = {

@@ -1094,6 +1093,7 @@ static const struct k_clock clock_boottime = {
 	.timer_set	= common_timer_set,
 	.timer_get	= common_timer_get,
 	.timer_del	= common_timer_del,
+	.timer_rearm	= common_hrtimer_rearm,
 };
 
 static const struct k_clock * const posix_clocks[] = {

index 02ffd1b..1f6f6f9 100644
@@ -28,5 +28,3 @@ extern const struct k_clock clock_thread;
 extern const struct k_clock alarm_clock;
 
 int posix_timer_event(struct k_itimer *timr, int si_private);
-
-void posix_cpu_timer_schedule(struct k_itimer *timer);

index 771e5f7..667095d 100644
@@ -59,6 +59,7 @@ struct cpu_timer_list {
  * @kclock:		Pointer to the k_clock struct handling this timer
  * @it_clock:		The posix timer clock id
  * @it_id:		The posix timer id for identifying the timer
+ * @it_active:		Marker that timer is active
  * @it_overrun:		The overrun counter for pending signals
  * @it_overrun_last:	The overrun at the time of the last delivered signal
  * @it_requeue_pending:	Indicator that timer waits for being requeued on

@@ -79,6 +80,7 @@ struct k_itimer {
 	const struct k_clock	*kclock;
 	clockid_t		it_clock;
 	timer_t			it_id;
+	int			it_active;
 	int			it_overrun;
 	int			it_overrun_last;
 	int			it_requeue_pending;

index b12582a..795215b 100644
@@ -316,6 +316,7 @@ void posixtimer_rearm(struct siginfo *info)
 	if (timr->it_requeue_pending == info->si_sys_private) {
 		timr->kclock->timer_rearm(timr);
 
+		timr->it_active = 1;
 		timr->it_overrun_last = timr->it_overrun;
 		timr->it_overrun = -1;
 		++timr->it_requeue_pending;

@@ -371,6 +372,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
 	timr = container_of(timer, struct k_itimer, it.real.timer);
 	spin_lock_irqsave(&timr->it_lock, flags);
 
+	timr->it_active = 0;
 	if (timr->it_interval != 0)
 		si_private = ++timr->it_requeue_pending;
 

@@ -418,6 +420,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
 						timr->it_interval);
 			ret = HRTIMER_RESTART;
 			++timr->it_requeue_pending;
+			timr->it_active = 1;
 		}
 	}
 

@@ -737,7 +740,8 @@ common_timer_set(struct k_itimer *timr, int flags,
 	if (hrtimer_try_to_cancel(timer) < 0)
 		return TIMER_RETRY;
 
-	timr->it_requeue_pending = (timr->it_requeue_pending + 2) & 
+	timr->it_active = 0;
+	timr->it_requeue_pending = (timr->it_requeue_pending + 2) &
 		~REQUEUE_PENDING;
 	timr->it_overrun_last = 0;
 

@@ -763,6 +767,7 @@ common_timer_set(struct k_itimer *timr, int flags,
 		return 0;
 	}
 
+	timr->it_active = 1;
 	hrtimer_start_expires(timer, mode);
 	return 0;
 }

@@ -821,6 +826,7 @@ static int common_timer_del(struct k_itimer *timer)
 
 	if (hrtimer_try_to_cancel(&timer->it.real.timer) < 0)
 		return TIMER_RETRY;
+	timer->it_active = 0;
 	return 0;
 }
 

index 1f6f6f9..3bc5b74 100644
@@ -19,6 +19,8 @@ struct k_clock {
 	void	(*timer_get)(struct k_itimer *timr,
 			     struct itimerspec64 *cur_setting);
 	void	(*timer_rearm)(struct k_itimer *timr);
+	int	(*timer_forward)(struct k_itimer *timr, ktime_t now);
+	ktime_t	(*timer_remaining)(struct k_itimer *timr, ktime_t now);
 };
 
 extern const struct k_clock clock_posix_cpu;

index 795215b..48f6c37 100644
@@ -607,6 +607,20 @@ static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
 	return NULL;
 }
 
+static ktime_t common_hrtimer_remaining(struct k_itimer *timr, ktime_t now)
+{
+	struct hrtimer *timer = &timr->it.real.timer;
+
+	return __hrtimer_expires_remaining_adjusted(timer, now);
+}
+
+static int common_hrtimer_forward(struct k_itimer *timr, ktime_t now)
+{
+	struct hrtimer *timer = &timr->it.real.timer;
+
+	return (int)hrtimer_forward(timer, now, timr->it_interval);
+}
+
 /*
  * Get the time remaining on a POSIX.1b interval timer.  This function
  * is ALWAYS called with spin_lock_irq on the timer, thus it must not

@@ -626,42 +640,54 @@ static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
 static void
 common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting)
 {
+	const struct k_clock *kc = timr->kclock;
 	ktime_t now, remaining, iv;
-	struct hrtimer *timer = &timr->it.real.timer;
+	struct timespec64 ts64;
+	bool sig_none;
 
 	memset(cur_setting, 0, sizeof(*cur_setting));
 
+	sig_none = (timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE;
 	iv = timr->it_interval;
 
 	/* interval timer ? */
-	if (iv)
+	if (iv) {
 		cur_setting->it_interval = ktime_to_timespec64(iv);
-	else if (!hrtimer_active(timer) &&
-		 (timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE)
-		return;
+	} else if (!timr->it_active) {
+		/*
+		 * SIGEV_NONE oneshot timers are never queued. Check them
+		 * below.
+		 */
+		if (!sig_none)
+			return;
+	}
 
-	now = timer->base->get_time();
+	/*
+	 * The timespec64 based conversion is suboptimal, but it's not
+	 * worth to implement yet another callback.
+	 */
+	kc->clock_get(timr->it_clock, &ts64);
+	now = timespec64_to_ktime(ts64);
 
 	/*
-	 * When a requeue is pending or this is a SIGEV_NONE
-	 * timer move the expiry time forward by intervals, so
-	 * expiry is > now.
+	 * When a requeue is pending or this is a SIGEV_NONE timer move the
+	 * expiry time forward by intervals, so expiry is > now.
 	 */
-	if (iv && (timr->it_requeue_pending & REQUEUE_PENDING ||
-		   (timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE))
-		timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv);
+	if (iv && (timr->it_requeue_pending & REQUEUE_PENDING || sig_none))
+		timr->it_overrun += kc->timer_forward(timr, now);
 
-	remaining = __hrtimer_expires_remaining_adjusted(timer, now);
+	remaining = kc->timer_remaining(timr, now);
 	/* Return 0 only, when the timer is expired and not pending */
 	if (remaining <= 0) {
 		/*
 		 * A single shot SIGEV_NONE timer must return 0, when
 		 * it is expired !
 		 */
-		if ((timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE)
+		if (!sig_none)
 			cur_setting->it_value.tv_nsec = 1;
-	} else
+	} else {
 		cur_setting->it_value = ktime_to_timespec64(remaining);
+	}
 }
 
 /* Get the time remaining on a POSIX.1b interval timer. */

@@ -1049,6 +1075,8 @@ static const struct k_clock clock_realtime = {
 	.timer_get	= common_timer_get,
 	.timer_del	= common_timer_del,
 	.timer_rearm	= common_hrtimer_rearm,
+	.timer_forward	= common_hrtimer_forward,
+	.timer_remaining= common_hrtimer_remaining,
 };
 
 static const struct k_clock clock_monotonic = {

@@ -1061,6 +1089,8 @@ static const struct k_clock clock_monotonic = {
 	.timer_get	= common_timer_get,
 	.timer_del	= common_timer_del,
 	.timer_rearm	= common_hrtimer_rearm,
+	.timer_forward	= common_hrtimer_forward,
+	.timer_remaining= common_hrtimer_remaining,
 };
 
 static const struct k_clock clock_monotonic_raw = {

@@ -1088,6 +1118,8 @@ static const struct k_clock clock_tai = {
 	.timer_get	= common_timer_get,
 	.timer_del	= common_timer_del,
 	.timer_rearm	= common_hrtimer_rearm,
+	.timer_forward	= common_hrtimer_forward,
+	.timer_remaining= common_hrtimer_remaining,
 };
 
 static const struct k_clock clock_boottime = {

@@ -1100,6 +1132,8 @@ static const struct k_clock clock_boottime = {
 	.timer_get	= common_timer_get,
 	.timer_del	= common_timer_del,
 	.timer_rearm	= common_hrtimer_rearm,
+	.timer_forward	= common_hrtimer_forward,
+	.timer_remaining= common_hrtimer_remaining,
 };
 
 static const struct k_clock * const posix_clocks[] = {

index 96c833a..cb4a4eb 100644
@@ -719,10 +719,8 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp
 	 */
 	itp->it_interval = ns_to_timespec64(timer->it.cpu.incr);
 
-	if (timer->it.cpu.expires == 0) {	/* Timer not armed at all.  */
-		itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
+	if (!timer->it.cpu.expires)
 		return;
-	}
 
 	/*
 	 * Sample the clock to take the difference with the expiry time.

@@ -746,7 +744,6 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp
 			 * Call the timer disarmed, nothing else to do.
 			 */
 			timer->it.cpu.expires = 0;
-			itp->it_value = ns_to_timespec64(timer->it.cpu.expires);
 			return;
 		} else {
 			cpu_timer_sample_group(timer->it_clock, p, &now);

index 48f6c37..0332f7a 100644
@@ -645,8 +645,6 @@ common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting)
 	struct timespec64 ts64;
 	bool sig_none;
 
-	memset(cur_setting, 0, sizeof(*cur_setting));
-
 	sig_none = (timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE;
 	iv = timr->it_interval;
 

@@ -705,6 +703,7 @@ SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
 	if (!timr)
 		return -EINVAL;
 
+	memset(&cur_setting64, 0, sizeof(cur_setting64));
 	kc = timr->kclock;
 	if (WARN_ON_ONCE(!kc || !kc->timer_get))
 		ret = -EINVAL;

index b53a0b5..88517dc 100644
@@ -828,6 +828,8 @@ SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
 	if (!timespec64_valid(&new_spec64.it_interval) ||
 	    !timespec64_valid(&new_spec64.it_value))
 		return -EINVAL;
+	if (rtn)
+		memset(rtn, 0, sizeof(*rtn));
 retry:
 	timr = lock_timer(timer_id, &flag);
 	if (!timr)