timers: Omit POSIX timer stuff from task_struct when disabled

When CONFIG_POSIX_TIMERS is disabled, it is preferable to remove related
structures from struct task_struct and struct signal_struct as they
won't contain anything useful and shouldn't be relied upon by mistake.
Code still referencing those structures is also disabled here.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>

2 files changed, 24 insertions, 12 deletions

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 2516b8df6dbb..a688a8206727 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2246,6 +2246,7 @@ prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
 	}
 }
 
+#ifdef CONFIG_POSIX_TIMERS
 static void watchdog(struct rq *rq, struct task_struct *p)
 {
 	unsigned long soft, hard;
@@ -2267,6 +2268,9 @@ static void watchdog(struct rq *rq, struct task_struct *p)
 			p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
 	}
 }
+#else
+static inline void watchdog(struct rq *rq, struct task_struct *p) { }
+#endif
 
 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
 {
diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h
index 34659a853505..c69a9870ab79 100644
--- a/kernel/sched/stats.h
+++ b/kernel/sched/stats.h
@@ -172,18 +172,19 @@ sched_info_switch(struct rq *rq,
  */
 
 /**
- * cputimer_running - return true if cputimer is running
+ * get_running_cputimer - return &tsk->signal->cputimer if cputimer is running
  *
  * @tsk:	Pointer to target task.
  */
-static inline bool cputimer_running(struct task_struct *tsk)
-
+#ifdef CONFIG_POSIX_TIMERS
+static inline
+struct thread_group_cputimer *get_running_cputimer(struct task_struct *tsk)
 {
 	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 
 	/* Check if cputimer isn't running. This is accessed without locking. */
 	if (!READ_ONCE(cputimer->running))
-		return false;
+		return NULL;
 
 	/*
 	 * After we flush the task's sum_exec_runtime to sig->sum_sched_runtime
@@ -200,10 +201,17 @@ static inline bool cputimer_running(struct task_struct *tsk)
 	 * clock delta is behind the expiring timer value.
 	 */
 	if (unlikely(!tsk->sighand))
-		return false;
+		return NULL;
 
-	return true;
+	return cputimer;
+}
+#else
+static inline
+struct thread_group_cputimer *get_running_cputimer(struct task_struct *tsk)
+{
+	return NULL;
 }
+#endif
 
 /**
  * account_group_user_time - Maintain utime for a thread group.
@@ -218,9 +226,9 @@ static inline bool cputimer_running(struct task_struct *tsk)
 static inline void account_group_user_time(struct task_struct *tsk,
 					   cputime_t cputime)
 {
-	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+	struct thread_group_cputimer *cputimer = get_running_cputimer(tsk);
 
-	if (!cputimer_running(tsk))
+	if (!cputimer)
 		return;
 
 	atomic64_add(cputime, &cputimer->cputime_atomic.utime);
@@ -239,9 +247,9 @@ static inline void account_group_user_time(struct task_struct *tsk,
 static inline void account_group_system_time(struct task_struct *tsk,
 					     cputime_t cputime)
 {
-	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+	struct thread_group_cputimer *cputimer = get_running_cputimer(tsk);
 
-	if (!cputimer_running(tsk))
+	if (!cputimer)
 		return;
 
 	atomic64_add(cputime, &cputimer->cputime_atomic.stime);
@@ -260,9 +268,9 @@ static inline void account_group_system_time(struct task_struct *tsk,
 static inline void account_group_exec_runtime(struct task_struct *tsk,
 					      unsigned long long ns)
 {
-	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+	struct thread_group_cputimer *cputimer = get_running_cputimer(tsk);
 
-	if (!cputimer_running(tsk))
+	if (!cputimer)
 		return;
 
 	atomic64_add(ns, &cputimer->cputime_atomic.sum_exec_runtime);