5 files changed, 27 insertions, 32 deletions

diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index fc50d2f959d1..e8cb9ff183e9 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -128,8 +128,6 @@ void *get_current(void)
         return current;
 }
 
-extern void schedule_tail(struct task_struct *prev);
-
 /*
  * This is called magically, by its address being stuffed in a jmp_buf
  * and being longjmp-d to.
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 96ee899d6502..91a1bd67ac1d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -314,9 +314,12 @@ static int proc_pid_schedstat(struct task_struct *task, char *buffer)
 static int lstats_show_proc(struct seq_file *m, void *v)
 {
         int i;
-        struct task_struct *task = m->private;
-        seq_puts(m, "Latency Top version : v0.1\n");
+        struct inode *inode = m->private;
+        struct task_struct *task = get_proc_task(inode);
 
+        if (!task)
+                return -ESRCH;
+        seq_puts(m, "Latency Top version : v0.1\n");
         for (i = 0; i < 32; i++) {
                 if (task->latency_record[i].backtrace[0]) {
                         int q;
@@ -341,32 +344,24 @@ static int lstats_show_proc(struct seq_file *m, void *v)
                 }
 
         }
+        put_task_struct(task);
         return 0;
 }
 
 static int lstats_open(struct inode *inode, struct file *file)
 {
-        int ret;
-        struct seq_file *m;
-        struct task_struct *task = get_proc_task(inode);
-
-        ret = single_open(file, lstats_show_proc, NULL);
-        if (!ret) {
-                m = file->private_data;
-                m->private = task;
-        }
-        return ret;
+        return single_open(file, lstats_show_proc, inode);
 }
 
 static ssize_t lstats_write(struct file *file, const char __user *buf,
                             size_t count, loff_t *offs)
 {
-        struct seq_file *m;
-        struct task_struct *task;
+        struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
 
-        m = file->private_data;
-        task = m->private;
+        if (!task)
+                return -ESRCH;
         clear_all_latency_tracing(task);
+        put_task_struct(task);
 
         return count;
 }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e217d188a102..9c17e828d6d4 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -242,6 +242,7 @@ struct task_struct;
 
 extern void sched_init(void);
 extern void sched_init_smp(void);
+extern asmlinkage void schedule_tail(struct task_struct *prev);
 extern void init_idle(struct task_struct *idle, int cpu);
 extern void init_idle_bootup_task(struct task_struct *idle);
 
diff --git a/kernel/sched.c b/kernel/sched.c
index b387a8de26a5..f06950c8a6ce 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -668,6 +668,8 @@ const_debug unsigned int sysctl_sched_nr_migrate = 32;
  */
 unsigned int sysctl_sched_rt_period = 1000000;
 
+static __read_mostly int scheduler_running;
+
 /*
  * part of the period that we allow rt tasks to run in us.
  * default: 0.95s
@@ -689,14 +691,16 @@ unsigned long long cpu_clock(int cpu)
         unsigned long flags;
         struct rq *rq;
 
-        local_irq_save(flags);
-        rq = cpu_rq(cpu);
         /*
          * Only call sched_clock() if the scheduler has already been
          * initialized (some code might call cpu_clock() very early):
          */
-        if (rq->idle)
-                update_rq_clock(rq);
+        if (unlikely(!scheduler_running))
+                return 0;
+
+        local_irq_save(flags);
+        rq = cpu_rq(cpu);
+        update_rq_clock(rq);
         now = rq->clock;
         local_irq_restore(flags);
 
@@ -3885,7 +3889,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev)
 asmlinkage void __sched schedule(void)
 {
         struct task_struct *prev, *next;
-        long *switch_count;
+        unsigned long *switch_count;
         struct rq *rq;
         int cpu;
 
@@ -7284,6 +7288,8 @@ void __init sched_init(void)
          * During early bootup we pretend to be a normal task:
          */
         current->sched_class = &fair_sched_class;
+
+        scheduler_running = 1;
 }
 
 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 6c091d6e159d..c8e6492c5925 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -202,17 +202,12 @@ static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
 
 static inline struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 {
-        struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
-        struct sched_entity *se = NULL;
-        struct rb_node *parent;
+        struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
 
-        while (*link) {
-                parent = *link;
-                se = rb_entry(parent, struct sched_entity, run_node);
-                link = &parent->rb_right;
-        }
+        if (!last)
+                return NULL;
 
-        return se;
+        return rb_entry(last, struct sched_entity, run_node);
 }
 
 /**************************************************************