Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/sc…

…m/linux/kernel/git/tip/tip

Pull timer fixes from Thomas Gleixner:
 "Three fixlets from the timer departement:

   - Update the timekeeper before updating vsyscall and pvclock.  This
     fixes the kvm-clock regression reported by Chris and Paolo.

   - Use the proper irq work interface from NMI.  This fixes the
     regression reported by Catalin and Dave.

   - Clarify the compat_nanosleep error handling mechanism to avoid
     future confusion"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timekeeping: Update timekeeper before updating vsyscall and pvclock
  compat: nanosleep: Clarify error handling
  nohz: Restore NMI safe local irq work for local nohz kick

include/linux/tick.h

@@ -183,13 +183,8 @@ static inline bool tick_nohz_full_cpu(int cpu)
 
 extern void tick_nohz_init(void);
 extern void __tick_nohz_full_check(void);
+extern void tick_nohz_full_kick(void);
 extern void tick_nohz_full_kick_cpu(int cpu);
-
-static inline void tick_nohz_full_kick(void)
-{
-	tick_nohz_full_kick_cpu(smp_processor_id());
-}
-
 extern void tick_nohz_full_kick_all(void);
 extern void __tick_nohz_task_switch(struct task_struct *tsk);
 #else

kernel/compat.c

@@ -226,7 +226,7 @@ static long compat_nanosleep_restart(struct restart_block *restart)
 	ret = hrtimer_nanosleep_restart(restart);
 	set_fs(oldfs);
 
-	if (ret) {
+	if (ret == -ERESTART_RESTARTBLOCK) {
 		rmtp = restart->nanosleep.compat_rmtp;
 
 		if (rmtp && compat_put_timespec(&rmt, rmtp))
@@ -256,7 +256,26 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp,
 				HRTIMER_MODE_REL, CLOCK_MONOTONIC);
 	set_fs(oldfs);
 
-	if (ret) {
+	/*
+	 * hrtimer_nanosleep() can only return 0 or
+	 * -ERESTART_RESTARTBLOCK here because:
+	 *
+	 * - we call it with HRTIMER_MODE_REL and therefor exclude the
+	 *   -ERESTARTNOHAND return path.
+	 *
+	 * - we supply the rmtp argument from the task stack (due to
+	 *   the necessary compat conversion. So the update cannot
+	 *   fail, which excludes the -EFAULT return path as well. If
+	 *   it fails nevertheless we have a bigger problem and wont
+	 *   reach this place anymore.
+	 *
+	 * - if the return value is 0, we do not have to update rmtp
+	 *    because there is no remaining time.
+	 *
+	 * We check for -ERESTART_RESTARTBLOCK nevertheless if the
+	 * core implementation decides to return random nonsense.
+	 */
+	if (ret == -ERESTART_RESTARTBLOCK) {
 		struct restart_block *restart
 			= &current_thread_info()->restart_block;
 
@@ -266,7 +285,6 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp,
 		if (rmtp && compat_put_timespec(&rmt, rmtp))
 			return -EFAULT;
 	}
-
 	return ret;
 }
 

kernel/time/tick-sched.c

@@ -224,6 +224,20 @@ static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
 	.func = nohz_full_kick_work_func,
 };
 
+/*
+ * Kick this CPU if it's full dynticks in order to force it to
+ * re-evaluate its dependency on the tick and restart it if necessary.
+ * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(),
+ * is NMI safe.
+ */
+void tick_nohz_full_kick(void)
+{
+	if (!tick_nohz_full_cpu(smp_processor_id()))
+		return;
+
+	irq_work_queue(&__get_cpu_var(nohz_full_kick_work));
+}
+
 /*
  * Kick the CPU if it's full dynticks in order to force it to
  * re-evaluate its dependency on the tick and restart it if necessary.

kernel/time/timekeeping.c

@@ -442,11 +442,12 @@ static void timekeeping_update(struct timekeeper *tk, unsigned int action)
 		tk->ntp_error = 0;
 		ntp_clear();
 	}
-	update_vsyscall(tk);
-	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
 
 	tk_update_ktime_data(tk);
 
+	update_vsyscall(tk);
+	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
+
 	if (action & TK_MIRROR)
 		memcpy(&shadow_timekeeper, &tk_core.timekeeper,
 		       sizeof(tk_core.timekeeper));