Merge branch 'wip-nested-locking' into tegra-nested-lockingwip-nested-locking

Conflicts:
	Makefile
	include/linux/fs.h

9 files changed, 320 insertions, 20 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 9e316ae4984..9d13da8a8c2 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -57,6 +57,8 @@
 #include <asm/pgtable.h>
 #include <asm/mmu_context.h>
 
+extern void exit_od_table(struct task_struct *t);
+
 static void exit_mm(struct task_struct * tsk);
 
 static void __unhash_process(struct task_struct *p, bool group_dead)
@@ -970,6 +972,8 @@ NORET_TYPE void do_exit(long code)
         if (unlikely(tsk->audit_context))
                 audit_free(tsk);
 
+        exit_od_table(tsk);
+
         tsk->exit_code = code;
         taskstats_exit(tsk, group_dead);
 
diff --git a/kernel/fork.c b/kernel/fork.c
index f65fa0627c0..067992d4838 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -76,6 +76,9 @@
 
 #include <trace/events/sched.h>
 
+#include <litmus/litmus.h>
+#include <litmus/sched_plugin.h>
+
 /*
  * Protected counters by write_lock_irq(&tasklist_lock)
  */
@@ -205,6 +208,7 @@ void __put_task_struct(struct task_struct *tsk)
         WARN_ON(atomic_read(&tsk->usage));
         WARN_ON(tsk == current);
 
+        exit_litmus(tsk);
         exit_creds(tsk);
         delayacct_tsk_free(tsk);
         put_signal_struct(tsk->signal);
@@ -290,6 +294,9 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
 
         tsk->stack = ti;
 
+        /* Don't let the new task be a real-time task. */
+        litmus_fork(tsk);
+
         err = prop_local_init_single(&tsk->dirties);
         if (err)
                 goto out;
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 2043c08d36c..2391745f656 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -46,6 +46,8 @@
 #include <linux/sched.h>
 #include <linux/timer.h>
 
+#include <litmus/litmus.h>
+
 #include <asm/uaccess.h>
 
 #include <trace/events/timer.h>
@@ -1028,6 +1030,98 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
 }
 EXPORT_SYMBOL_GPL(hrtimer_start);
 
+#ifdef CONFIG_ARCH_HAS_SEND_PULL_TIMERS
+
+/**
+ * hrtimer_start_on_info_init - Initialize hrtimer_start_on_info
+ */
+void hrtimer_start_on_info_init(struct hrtimer_start_on_info *info)
+{
+        memset(info, 0, sizeof(struct hrtimer_start_on_info));
+        atomic_set(&info->state, HRTIMER_START_ON_INACTIVE);
+}
+
+/**
+ *  hrtimer_pull - PULL_TIMERS_VECTOR callback on remote cpu
+ */
+void hrtimer_pull(void)
+{
+        struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);
+        struct hrtimer_start_on_info *info;
+        struct list_head *pos, *safe, list;
+
+        raw_spin_lock(&base->lock);
+        list_replace_init(&base->to_pull, &list);
+        raw_spin_unlock(&base->lock);
+
+        list_for_each_safe(pos, safe, &list) {
+                info = list_entry(pos, struct hrtimer_start_on_info, list);
+                TRACE("pulled timer 0x%x\n", info->timer);
+                list_del(pos);
+                hrtimer_start(info->timer, info->time, info->mode);
+        }
+}
+
+/**
+ *  hrtimer_start_on - trigger timer arming on remote cpu
+ *  @cpu:       remote cpu
+ *  @info:      save timer information for enqueuing on remote cpu
+ *  @timer:     timer to be pulled
+ *  @time:      expire time
+ *  @mode:      timer mode
+ */
+int hrtimer_start_on(int cpu, struct hrtimer_start_on_info* info,
+                struct hrtimer *timer, ktime_t time,
+                const enum hrtimer_mode mode)
+{
+        unsigned long flags;
+        struct hrtimer_cpu_base* base;
+        int in_use = 0, was_empty;
+
+        /* serialize access to info through the timer base */
+        lock_hrtimer_base(timer, &flags);
+
+        in_use = (atomic_read(&info->state) != HRTIMER_START_ON_INACTIVE);
+        if (!in_use) {
+                INIT_LIST_HEAD(&info->list);
+                info->timer = timer;
+                info->time  = time;
+                info->mode  = mode;
+                /* mark as in use */
+                atomic_set(&info->state, HRTIMER_START_ON_QUEUED);
+        }
+
+        unlock_hrtimer_base(timer, &flags);
+
+        if (!in_use) {
+                /* initiate pull  */
+                preempt_disable();
+                if (cpu == smp_processor_id()) {
+                        /* start timer locally; we may get called
+                         * with rq->lock held, do not wake up anything
+                         */
+                        TRACE("hrtimer_start_on: starting on local CPU\n");
+                        __hrtimer_start_range_ns(info->timer, info->time,
+                                                 0, info->mode, 0);
+                } else {
+                        TRACE("hrtimer_start_on: pulling to remote CPU\n");
+                        base = &per_cpu(hrtimer_bases, cpu);
+                        raw_spin_lock_irqsave(&base->lock, flags);
+                        was_empty = list_empty(&base->to_pull);
+                        list_add(&info->list, &base->to_pull);
+                        raw_spin_unlock_irqrestore(&base->lock, flags);
+                        if (was_empty)
+                                /* only send IPI if other no else
+                                 * has done so already
+                                 */
+                                smp_send_pull_timers(cpu);
+                }
+                preempt_enable();
+        }
+        return in_use;
+}
+
+#endif
 
 /**
  * hrtimer_try_to_cancel - try to deactivate a timer
@@ -1627,6 +1721,7 @@ static void __cpuinit init_hrtimers_cpu(int cpu)
         }
 
         hrtimer_init_hres(cpu_base);
+        INIT_LIST_HEAD(&cpu_base->to_pull);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
diff --git a/kernel/printk.c b/kernel/printk.c
index 1baace7d867..cbebc142be1 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -74,6 +74,13 @@ int console_printk[4] = {
 };
 
 /*
+ * divert printk() messages when there is a LITMUS^RT debug listener
+ */
+#include <litmus/litmus.h>
+int trace_override = 0;
+int trace_recurse  = 0;
+
+/*
  * Low level drivers may need that to know if they can schedule in
  * their unblank() callback or not. So let's export it.
  */
@@ -926,6 +933,9 @@ asmlinkage int vprintk(const char *fmt, va_list args)
         /* Emit the output into the temporary buffer */
         printed_len += vscnprintf(printk_buf + printed_len,
                                   sizeof(printk_buf) - printed_len, fmt, args);
+        /* if LITMUS^RT tracer is active divert printk() msgs */
+        if (trace_override && !trace_recurse)
+                TRACE("%s", printk_buf);
 
 #ifdef  CONFIG_DEBUG_LL
         printascii(printk_buf);
@@ -1006,7 +1016,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
          * Try to acquire and then immediately release the
          * console semaphore. The release will do all the
          * actual magic (print out buffers, wake up klogd,
-         * etc). 
+         * etc).
          *
          * The console_trylock_for_printk() function
          * will release 'logbuf_lock' regardless of whether it
@@ -1278,7 +1288,7 @@ int printk_needs_cpu(int cpu)
 
 void wake_up_klogd(void)
 {
-        if (waitqueue_active(&log_wait))
+        if (!trace_override && waitqueue_active(&log_wait))
                 this_cpu_write(printk_pending, 1);
 }
 
diff --git a/kernel/sched.c b/kernel/sched.c
index f6cf5cbc64b..a1bf2646d12 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -87,6 +87,11 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/sched.h>
 
+#include <litmus/sched_trace.h>
+#include <litmus/trace.h>
+
+static void litmus_tick(struct rq*, struct task_struct*);
+
 /*
  * Convert user-nice values [ -20 ... 0 ... 19 ]
  * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
@@ -414,6 +419,12 @@ struct rt_rq {
 #endif
 };
 
+/* Litmus related fields in a runqueue */
+struct litmus_rq {
+        unsigned long nr_running;
+        struct task_struct *prev;
+};
+
 #ifdef CONFIG_SMP
 
 /*
@@ -479,6 +490,7 @@ struct rq {
 
         struct cfs_rq cfs;
         struct rt_rq rt;
+        struct litmus_rq litmus;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
         /* list of leaf cfs_rq on this cpu: */
@@ -1054,6 +1066,7 @@ static enum hrtimer_restart hrtick(struct hrtimer *timer)
         raw_spin_lock(&rq->lock);
         update_rq_clock(rq);
         rq->curr->sched_class->task_tick(rq, rq->curr, 1);
+        litmus_tick(rq, rq->curr);
         raw_spin_unlock(&rq->lock);
 
         return HRTIMER_NORESTART;
@@ -1750,7 +1763,7 @@ static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
 
 static const struct sched_class rt_sched_class;
 
-#define sched_class_highest (&stop_sched_class)
+#define sched_class_highest (&litmus_sched_class)
 #define for_each_class(class) \
    for (class = sched_class_highest; class; class = class->next)
 
@@ -2044,6 +2057,7 @@ static int irqtime_account_si_update(void)
 #include "sched_rt.c"
 #include "sched_autogroup.c"
 #include "sched_stoptask.c"
+#include "../litmus/sched_litmus.c"
 #ifdef CONFIG_SCHED_DEBUG
 # include "sched_debug.c"
 #endif
@@ -2166,6 +2180,10 @@ static void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
          * A queue event has occurred, and we're going to schedule.  In
          * this case, we can save a useless back to back clock update.
          */
+        /* LITMUS^RT:
+         * The "disable-clock-update" approach was buggy in Linux 2.6.36.
+         * The issue has been solved in 2.6.37.
+         */
         if (rq->curr->on_rq && test_tsk_need_resched(rq->curr))
                 rq->skip_clock_update = 1;
 }
@@ -2592,8 +2610,12 @@ void scheduler_ipi(void)
         struct rq *rq = this_rq();
         struct task_struct *list = xchg(&rq->wake_list, NULL);
 
-        if (!list)
+        if (!list) {
+                /* If we don't call irq_enter(), we need to trigger the IRQ
+                 * tracing manually. */
+                ft_irq_fired();
                 return;
+        }
 
         /*
          * Not all reschedule IPI handlers call irq_enter/irq_exit, since
@@ -2656,7 +2678,12 @@ static void ttwu_queue(struct task_struct *p, int cpu)
         struct rq *rq = cpu_rq(cpu);
 
 #if defined(CONFIG_SMP)
-        if (sched_feat(TTWU_QUEUE) && cpu != smp_processor_id()) {
+        /*
+         * LITMUS^RT: whether to send an IPI to the remote CPU
+         * is plugin specific.
+         */
+        if (!is_realtime(p) &&
+                        sched_feat(TTWU_QUEUE) && cpu != smp_processor_id()) {
                 sched_clock_cpu(cpu); /* sync clocks x-cpu */
                 ttwu_queue_remote(p, cpu);
                 return;
@@ -2689,6 +2716,9 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
         unsigned long flags;
         int cpu, success = 0;
 
+        if (is_realtime(p))
+                TRACE_TASK(p, "try_to_wake_up() state:%d\n", p->state);
+
         smp_wmb();
         raw_spin_lock_irqsave(&p->pi_lock, flags);
         if (!(p->state & state))
@@ -2725,6 +2755,12 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
          */
         smp_rmb();
 
+        /* LITMUS^RT: once the task can be safely referenced by this
+         * CPU, don't mess up with Linux load balancing stuff.
+         */
+        if (is_realtime(p))
+                goto litmus_out_activate;
+
         p->sched_contributes_to_load = !!task_contributes_to_load(p);
         p->state = TASK_WAKING;
 
@@ -2736,12 +2772,16 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
                 wake_flags |= WF_MIGRATED;
                 set_task_cpu(p, cpu);
         }
+
+litmus_out_activate:
 #endif /* CONFIG_SMP */
 
         ttwu_queue(p, cpu);
 stat:
         ttwu_stat(p, cpu, wake_flags);
 out:
+        if (is_realtime(p))
+                TRACE_TASK(p, "try_to_wake_up() done state:%d\n", p->state);
         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
 
         return success;
@@ -2852,7 +2892,8 @@ void sched_fork(struct task_struct *p)
          * Revert to default priority/policy on fork if requested.
          */
         if (unlikely(p->sched_reset_on_fork)) {
-                if (p->policy == SCHED_FIFO || p->policy == SCHED_RR) {
+                if (p->policy == SCHED_FIFO || p->policy == SCHED_RR ||
+                    p->policy == SCHED_LITMUS) {
                         p->policy = SCHED_NORMAL;
                         p->normal_prio = p->static_prio;
                 }
@@ -3063,6 +3104,8 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
          */
         prev_state = prev->state;
         finish_arch_switch(prev);
+        litmus->finish_switch(prev);
+        prev->rt_param.stack_in_use = NO_CPU;
 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
         local_irq_disable();
 #endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
@@ -3092,6 +3135,15 @@ static inline void pre_schedule(struct rq *rq, struct task_struct *prev)
 {
         if (prev->sched_class->pre_schedule)
                 prev->sched_class->pre_schedule(rq, prev);
+
+        /* LITMUS^RT not very clean hack: we need to save the prev task
+         * as our scheduling decision rely on it (as we drop the rq lock
+         * something in prev can change...); there is no way to escape
+         * this ack apart from modifying pick_nex_task(rq, _prev_) or
+         * falling back on the previous solution of decoupling
+         * scheduling decisions
+         */
+        rq->litmus.prev = prev;
 }
 
 /* rq->lock is NOT held, but preemption is disabled */
@@ -3128,16 +3180,26 @@ static inline void post_schedule(struct rq *rq)
 asmlinkage void schedule_tail(struct task_struct *prev)
         __releases(rq->lock)
 {
-        struct rq *rq = this_rq();
-
+        struct rq *rq;
+        
+        preempt_disable();
+        
+        rq = this_rq();
         finish_task_switch(rq, prev);
 
+        sched_trace_task_switch_to(current);
+
         /*
          * FIXME: do we need to worry about rq being invalidated by the
          * task_switch?
          */
         post_schedule(rq);
 
+        if (sched_state_validate_switch())
+                litmus_reschedule_local();
+
+        preempt_enable();
+
 #ifdef __ARCH_WANT_UNLOCKED_CTXSW
         /* In this case, finish_task_switch does not reenable preemption */
         preempt_enable();
@@ -4108,18 +4170,26 @@ void scheduler_tick(void)
 
         sched_clock_tick();
 
+        TS_TICK_START(current);
+
         raw_spin_lock(&rq->lock);
         update_rq_clock(rq);
         update_cpu_load_active(rq);
         curr->sched_class->task_tick(rq, curr, 0);
+
+        /* litmus_tick may force current to resched */
+        litmus_tick(rq, curr);
+
         raw_spin_unlock(&rq->lock);
 
         perf_event_task_tick();
 
 #ifdef CONFIG_SMP
         rq->idle_at_tick = idle_cpu(cpu);
-        trigger_load_balance(rq, cpu);
+        if (!is_realtime(current))
+                trigger_load_balance(rq, cpu);
 #endif
+        TS_TICK_END(current);
 }
 
 notrace unsigned long get_parent_ip(unsigned long addr)
@@ -4239,12 +4309,20 @@ pick_next_task(struct rq *rq)
         /*
          * Optimization: we know that if all tasks are in
          * the fair class we can call that function directly:
-         */
-        if (likely(rq->nr_running == rq->cfs.nr_running)) {
+
+         * NOT IN LITMUS^RT!
+
+         * This breaks many assumptions in the plugins.
+         * Do not uncomment without thinking long and hard
+         * about how this affects global plugins such as GSN-EDF.
+
+        if (rq->nr_running == rq->cfs.nr_running) {
+                TRACE("taking shortcut in pick_next_task()\n");
                 p = fair_sched_class.pick_next_task(rq);
                 if (likely(p))
                         return p;
         }
+        */
 
         for_each_class(class) {
                 p = class->pick_next_task(rq);
@@ -4267,11 +4345,19 @@ static void __sched __schedule(void)
 
 need_resched:
         preempt_disable();
+        sched_state_entered_schedule();
         cpu = smp_processor_id();
         rq = cpu_rq(cpu);
         rcu_note_context_switch(cpu);
         prev = rq->curr;
 
+        /* LITMUS^RT: quickly re-evaluate the scheduling decision
+         * if the previous one is no longer valid after CTX.
+         */
+litmus_need_resched_nonpreemptible:
+        TS_SCHED_START;
+        sched_trace_task_switch_away(prev);
+
         schedule_debug(prev);
 
         if (sched_feat(HRTICK))
@@ -4318,7 +4404,10 @@ need_resched:
                 rq->curr = next;
                 ++*switch_count;
 
+                TS_SCHED_END(next);
+                TS_CXS_START(next);
                 context_switch(rq, prev, next); /* unlocks the rq */
+                TS_CXS_END(current);
                 /*
                  * The context switch have flipped the stack from under us
                  * and restored the local variables which were saved when
@@ -4327,14 +4416,29 @@ need_resched:
                  */
                 cpu = smp_processor_id();
                 rq = cpu_rq(cpu);
-        } else
+        } else {
+                TS_SCHED_END(prev);
                 raw_spin_unlock_irq(&rq->lock);
+        }
+
+        TS_SCHED2_START(prev);
+        sched_trace_task_switch_to(current);
 
         post_schedule(rq);
 
+        if (sched_state_validate_switch()) {
+                TS_SCHED2_END(prev);
+                goto litmus_need_resched_nonpreemptible;
+        }
+
         preempt_enable_no_resched();
+
+        TS_SCHED2_END(prev);
+
         if (need_resched())
                 goto need_resched;
+
+        srp_ceiling_block();
 }
 
 static inline void sched_submit_work(struct task_struct *tsk)
@@ -5056,7 +5160,9 @@ __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
         p->normal_prio = normal_prio(p);
         /* we are holding p->pi_lock already */
         p->prio = rt_mutex_getprio(p);
-        if (rt_prio(p->prio))
+        if (p->policy == SCHED_LITMUS)
+                p->sched_class = &litmus_sched_class;
+        else if (rt_prio(p->prio))
                 p->sched_class = &rt_sched_class;
         else
                 p->sched_class = &fair_sched_class;
@@ -5104,7 +5210,7 @@ recheck:
 
                 if (policy != SCHED_FIFO && policy != SCHED_RR &&
                                 policy != SCHED_NORMAL && policy != SCHED_BATCH &&
-                                policy != SCHED_IDLE)
+                                policy != SCHED_IDLE && policy != SCHED_LITMUS)
                         return -EINVAL;
         }
 
@@ -5119,6 +5225,8 @@ recheck:
                 return -EINVAL;
         if (rt_policy(policy) != (param->sched_priority != 0))
                 return -EINVAL;
+        if (policy == SCHED_LITMUS && policy == p->policy)
+                return -EINVAL;
 
         /*
          * Allow unprivileged RT tasks to decrease priority:
@@ -5162,6 +5270,12 @@ recheck:
                         return retval;
         }
 
+        if (policy == SCHED_LITMUS) {
+                retval = litmus_admit_task(p);
+                if (retval)
+                        return retval;
+        }
+
         /*
          * make sure no PI-waiters arrive (or leave) while we are
          * changing the priority of the task:
@@ -5220,10 +5334,19 @@ recheck:
 
         p->sched_reset_on_fork = reset_on_fork;
 
+        if (p->policy == SCHED_LITMUS)
+                litmus_exit_task(p);
+
         oldprio = p->prio;
         prev_class = p->sched_class;
         __setscheduler(rq, p, policy, param->sched_priority);
 
+        if (policy == SCHED_LITMUS) {
+                p->rt_param.stack_in_use = running ? rq->cpu : NO_CPU;
+                p->rt_param.present = running;
+                litmus->task_new(p, on_rq, running);
+        }
+
         if (running)
                 p->sched_class->set_curr_task(rq);
         if (on_rq)
@@ -5391,10 +5514,11 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
         rcu_read_lock();
 
         p = find_process_by_pid(pid);
-        if (!p) {
+        /* Don't set affinity if task not found and for LITMUS tasks */
+        if (!p || is_realtime(p)) {
                 rcu_read_unlock();
                 put_online_cpus();
-                return -ESRCH;
+                return p ? -EPERM : -ESRCH;
         }
 
         /* Prevent p going away */
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index bc8ee999381..22999b257ad 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1872,6 +1872,9 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
         int scale = cfs_rq->nr_running >= sched_nr_latency;
         int next_buddy_marked = 0;
 
+        if (unlikely(rt_prio(p->prio)) || p->policy == SCHED_LITMUS)
+                goto preempt;
+
         if (unlikely(se == pse))
                 return;
 
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index af1177858be..b827550a0d0 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -3,6 +3,8 @@
  * policies)
  */
 
+#include <litmus/litmus.h>
+
 #ifdef CONFIG_RT_GROUP_SCHED
 
 #define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
@@ -240,8 +242,11 @@ static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
         if (rt_rq->rt_nr_running) {
                 if (rt_se && !on_rt_rq(rt_se))
                         enqueue_rt_entity(rt_se, false);
-                if (rt_rq->highest_prio.curr < curr->prio)
+                if (rt_rq->highest_prio.curr < curr->prio &&
+                    /* Don't subject LITMUS tasks to remote reschedules */
+                    !is_realtime(curr)) {
                         resched_task(curr);
+                }
         }
 }
 
@@ -334,8 +339,10 @@ static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 
 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 {
-        if (rt_rq->rt_nr_running)
-                resched_task(rq_of_rt_rq(rt_rq)->curr);
+        struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
+
+        if (rt_rq->rt_nr_running && !is_realtime(curr))
+                resched_task(curr);
 }
 
 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
@@ -1090,7 +1097,7 @@ static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
  */
 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
 {
-        if (p->prio < rq->curr->prio) {
+        if (p->prio < rq->curr->prio || p->policy == SCHED_LITMUS) {
                 resched_task(rq->curr);
                 return;
         }
diff --git a/kernel/softirq.c b/kernel/softirq.c
index fca82c32042..2f2df08df39 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -211,6 +211,9 @@ asmlinkage void __do_softirq(void)
         int max_restart = MAX_SOFTIRQ_RESTART;
         int cpu;
 
+        /* Mark Feather-Trace samples as "disturbed". */
+        ft_irq_fired();
+
         pending = local_softirq_pending();
         account_system_vtime(current);
 
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d5097c44b40..0c0e02f1b81 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -766,12 +766,53 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
 }
 
 /**
+ * tick_set_quanta_type - get the quanta type as a boot option
+ * Default is standard setup with ticks staggered over first
+ * half of tick period.
+ */
+int quanta_type = LINUX_DEFAULT_TICKS;
+static int __init tick_set_quanta_type(char *str)
+{
+        if (strcmp("aligned", str) == 0) {
+                quanta_type = LITMUS_ALIGNED_TICKS;
+                printk(KERN_INFO "LITMUS^RT: setting aligned quanta\n");
+        }
+        else if (strcmp("staggered", str) == 0) {
+                quanta_type = LITMUS_STAGGERED_TICKS;
+                printk(KERN_INFO "LITMUS^RT: setting staggered quanta\n");
+        }
+        return 1;
+}
+__setup("quanta=", tick_set_quanta_type);
+
+u64 cpu_stagger_offset(int cpu)
+{
+        u64 offset = 0;
+        switch (quanta_type) {
+                case LITMUS_ALIGNED_TICKS:
+                        offset = 0;
+                        break;
+                case LITMUS_STAGGERED_TICKS:
+                        offset = ktime_to_ns(tick_period);
+                        do_div(offset, num_possible_cpus());
+                        offset *= cpu;
+                        break;
+                default:
+                        offset = ktime_to_ns(tick_period) >> 1;
+                        do_div(offset, num_possible_cpus());
+                        offset *= cpu;
+        }
+        return offset;
+}
+
+/**
  * tick_setup_sched_timer - setup the tick emulation timer
  */
 void tick_setup_sched_timer(void)
 {
         struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
         ktime_t now = ktime_get();
+        u64 offset;
 
         /*
          * Emulate tick processing via per-CPU hrtimers:
@@ -782,6 +823,12 @@ void tick_setup_sched_timer(void)
         /* Get the next period (per cpu) */
         hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
 
+        /* Offset must be set correctly to achieve desired quanta type. */
+        offset = cpu_stagger_offset(smp_processor_id());
+
+        /* Add the correct offset to expiration time */
+        hrtimer_add_expires_ns(&ts->sched_timer, offset);
+
         for (;;) {
                 hrtimer_forward(&ts->sched_timer, now, tick_period);
                 hrtimer_start_expires(&ts->sched_timer,