15 files changed, 251 insertions, 75 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index cb8a15c19583..b675a67c9ac3 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -43,6 +43,8 @@
 #include <linux/seq_file.h>
 #include <linux/err.h>
 #include <linux/debugobjects.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
 
 #include <asm/uaccess.h>
 
@@ -193,12 +195,24 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
  * Switch the timer base to the current CPU when possible.
  */
 static inline struct hrtimer_clock_base *
-switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base)
+switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
+                    int pinned)
 {
         struct hrtimer_clock_base *new_base;
         struct hrtimer_cpu_base *new_cpu_base;
+        int cpu, preferred_cpu = -1;
+
+        cpu = smp_processor_id();
+#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
+        if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu)) {
+                preferred_cpu = get_nohz_load_balancer();
+                if (preferred_cpu >= 0)
+                        cpu = preferred_cpu;
+        }
+#endif
 
-        new_cpu_base = &__get_cpu_var(hrtimer_bases);
+again:
+        new_cpu_base = &per_cpu(hrtimer_bases, cpu);
         new_base = &new_cpu_base->clock_base[base->index];
 
         if (base != new_base) {
@@ -218,6 +232,40 @@ switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base)
                 timer->base = NULL;
                 spin_unlock(&base->cpu_base->lock);
                 spin_lock(&new_base->cpu_base->lock);
+
+                /* Optimized away for NOHZ=n SMP=n */
+                if (cpu == preferred_cpu) {
+                        /* Calculate clock monotonic expiry time */
+#ifdef CONFIG_HIGH_RES_TIMERS
+                        ktime_t expires = ktime_sub(hrtimer_get_expires(timer),
+                                                        new_base->offset);
+#else
+                        ktime_t expires = hrtimer_get_expires(timer);
+#endif
+
+                        /*
+                         * Get the next event on target cpu from the
+                         * clock events layer.
+                         * This covers the highres=off nohz=on case as well.
+                         */
+                        ktime_t next = clockevents_get_next_event(cpu);
+
+                        ktime_t delta = ktime_sub(expires, next);
+
+                        /*
+                         * We do not migrate the timer when it is expiring
+                         * before the next event on the target cpu because
+                         * we cannot reprogram the target cpu hardware and
+                         * we would cause it to fire late.
+                         */
+                        if (delta.tv64 < 0) {
+                                cpu = smp_processor_id();
+                                spin_unlock(&new_base->cpu_base->lock);
+                                spin_lock(&base->cpu_base->lock);
+                                timer->base = base;
+                                goto again;
+                        }
+                }
                 timer->base = new_base;
         }
         return new_base;
@@ -235,7 +283,7 @@ lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
         return base;
 }
 
-# define switch_hrtimer_base(t, b)      (b)
+# define switch_hrtimer_base(t, b, p)   (b)
 
 #endif  /* !CONFIG_SMP */
 
@@ -907,9 +955,9 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
         ret = remove_hrtimer(timer, base);
 
         /* Switch the timer base, if necessary: */
-        new_base = switch_hrtimer_base(timer, base);
+        new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
 
-        if (mode == HRTIMER_MODE_REL) {
+        if (mode & HRTIMER_MODE_REL) {
                 tim = ktime_add_safe(tim, new_base->get_time());
                 /*
                  * CONFIG_TIME_LOW_RES is a temporary way for architectures
diff --git a/kernel/module.c b/kernel/module.c
index e4ab36ce7672..215aaab09e91 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2899,7 +2899,7 @@ void print_modules(void)
         struct module *mod;
         char buf[8];
 
-        printk("Modules linked in:");
+        printk(KERN_DEFAULT "Modules linked in:");
         /* Most callers should already have preempt disabled, but make sure */
         preempt_disable();
         list_for_each_entry_rcu(mod, &modules, list)
diff --git a/kernel/printk.c b/kernel/printk.c
index 5052b5497c67..b4d97b54c1ec 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -687,20 +687,35 @@ asmlinkage int vprintk(const char *fmt, va_list args)
                                   sizeof(printk_buf) - printed_len, fmt, args);
 
 
+        p = printk_buf;
+
+        /* Do we have a loglevel in the string? */
+        if (p[0] == '<') {
+                unsigned char c = p[1];
+                if (c && p[2] == '>') {
+                        switch (c) {
+                        case '0' ... '7': /* loglevel */
+                                current_log_level = c - '0';
+                        /* Fallthrough - make sure we're on a new line */
+                        case 'd': /* KERN_DEFAULT */
+                                if (!new_text_line) {
+                                        emit_log_char('\n');
+                                        new_text_line = 1;
+                                }
+                        /* Fallthrough - skip the loglevel */
+                        case 'c': /* KERN_CONT */
+                                p += 3;
+                                break;
+                        }
+                }
+        }
+
         /*
          * Copy the output into log_buf.  If the caller didn't provide
          * appropriate log level tags, we insert them here
          */
-        for (p = printk_buf; *p; p++) {
+        for ( ; *p; p++) {
                 if (new_text_line) {
-                        /* If a token, set current_log_level and skip over */
-                        if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
-                            p[2] == '>') {
-                                current_log_level = p[1] - '0';
-                                p += 3;
-                                printed_len -= 3;
-                        }
-
                         /* Always output the token */
                         emit_log_char('<');
                         emit_log_char(current_log_level + '0');
diff --git a/kernel/sched.c b/kernel/sched.c
index 8ec9d13140be..8fb88a906aaa 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -240,7 +240,7 @@ static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
                 hard = hrtimer_get_expires(&rt_b->rt_period_timer);
                 delta = ktime_to_ns(ktime_sub(hard, soft));
                 __hrtimer_start_range_ns(&rt_b->rt_period_timer, soft, delta,
-                                HRTIMER_MODE_ABS, 0);
+                                HRTIMER_MODE_ABS_PINNED, 0);
         }
         spin_unlock(&rt_b->rt_runtime_lock);
 }
@@ -1155,7 +1155,7 @@ static __init void init_hrtick(void)
 static void hrtick_start(struct rq *rq, u64 delay)
 {
         __hrtimer_start_range_ns(&rq->hrtick_timer, ns_to_ktime(delay), 0,
-                        HRTIMER_MODE_REL, 0);
+                        HRTIMER_MODE_REL_PINNED, 0);
 }
 
 static inline void init_hrtick(void)
@@ -4397,6 +4397,11 @@ static struct {
         .load_balancer = ATOMIC_INIT(-1),
 };
 
+int get_nohz_load_balancer(void)
+{
+        return atomic_read(&nohz.load_balancer);
+}
+
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
 /**
  * lowest_flag_domain - Return lowest sched_domain containing flag.
@@ -9029,6 +9034,8 @@ void __init sched_init_smp(void)
 }
 #endif /* CONFIG_SMP */
 
+const_debug unsigned int sysctl_timer_migration = 1;
+
 int in_sched_functions(unsigned long addr)
 {
         return in_lock_functions(addr) ||
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 9ef80bba3509..f5c76b6cd616 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -329,6 +329,14 @@ static struct ctl_table kern_table[] = {
                 .mode           = 0644,
                 .proc_handler   = &proc_dointvec,
         },
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "timer_migration",
+                .data           = &sysctl_timer_migration,
+                .maxlen         = sizeof(unsigned int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec,
+        },
 #endif
         {
                 .ctl_name       = CTL_UNNUMBERED,
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index d13be216a790..1ad6dd461119 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -18,6 +18,7 @@
 #include <linux/notifier.h>
 #include <linux/smp.h>
 #include <linux/sysdev.h>
+#include <linux/tick.h>
 
 /* The registered clock event devices */
 static LIST_HEAD(clockevent_devices);
@@ -54,6 +55,7 @@ unsigned long clockevent_delta2ns(unsigned long latch,
 
         return (unsigned long) clc;
 }
+EXPORT_SYMBOL_GPL(clockevent_delta2ns);
 
 /**
  * clockevents_set_mode - set the operating mode of a clock event device
@@ -187,6 +189,7 @@ void clockevents_register_device(struct clock_event_device *dev)
 
         spin_unlock(&clockevents_lock);
 }
+EXPORT_SYMBOL_GPL(clockevents_register_device);
 
 /*
  * Noop handler when we shut down an event device
@@ -251,4 +254,15 @@ void clockevents_notify(unsigned long reason, void *arg)
         spin_unlock(&clockevents_lock);
 }
 EXPORT_SYMBOL_GPL(clockevents_notify);
+
+ktime_t clockevents_get_next_event(int cpu)
+{
+        struct tick_device *td;
+        struct clock_event_device *dev;
+
+        td = &per_cpu(tick_cpu_device, cpu);
+        dev = td->evtdev;
+
+        return dev->next_event;
+}
 #endif
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 80189f6f1c5a..592bf584d1d2 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -509,6 +509,18 @@ static ssize_t sysfs_override_clocksource(struct sys_device *dev,
                 }
         }
 
+        /*
+         * Check to make sure we don't switch to a non-highres capable
+         * clocksource if the tick code is in oneshot mode (highres or nohz)
+         */
+        if (tick_oneshot_mode_active() &&
+            !(ovr->flags & CLOCK_SOURCE_VALID_FOR_HRES)) {
+                printk(KERN_WARNING "%s clocksource is not HRT compatible. "
+                        "Cannot switch while in HRT/NOHZ mode\n", ovr->name);
+                ovr = NULL;
+                override_name[0] = 0;
+        }
+
         /* Reselect, when the override name has changed */
         if (ovr != clocksource_override) {
                 clocksource_override = ovr;
@@ -537,7 +549,13 @@ sysfs_show_available_clocksources(struct sys_device *dev,
 
         spin_lock_irq(&clocksource_lock);
         list_for_each_entry(src, &clocksource_list, list) {
-                count += snprintf(buf + count,
+                /*
+                 * Don't show non-HRES clocksource if the tick code is
+                 * in one shot mode (highres=on or nohz=on)
+                 */
+                if (!tick_oneshot_mode_active() ||
+                    (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
+                        count += snprintf(buf + count,
                                   max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
                                   "%s ", src->name);
         }
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 118a3b3b3f9a..877dbedc3118 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -27,7 +27,7 @@
  * timer stops in C3 state.
  */
 
-struct tick_device tick_broadcast_device;
+static struct tick_device tick_broadcast_device;
 /* FIXME: Use cpumask_var_t. */
 static DECLARE_BITMAP(tick_broadcast_mask, NR_CPUS);
 static DECLARE_BITMAP(tmpmask, NR_CPUS);
diff --git a/kernel/time/tick-oneshot.c b/kernel/time/tick-oneshot.c
index 2e8de678e767..a96c0e2b89cf 100644
--- a/kernel/time/tick-oneshot.c
+++ b/kernel/time/tick-oneshot.c
@@ -128,6 +128,23 @@ int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
         return 0;
 }
 
+/**
+ * tick_check_oneshot_mode - check whether the system is in oneshot mode
+ *
+ * returns 1 when either nohz or highres are enabled. otherwise 0.
+ */
+int tick_oneshot_mode_active(void)
+{
+        unsigned long flags;
+        int ret;
+
+        local_irq_save(flags);
+        ret = __get_cpu_var(tick_cpu_device).mode == TICKDEV_MODE_ONESHOT;
+        local_irq_restore(flags);
+
+        return ret;
+}
+
 #ifdef CONFIG_HIGH_RES_TIMERS
 /**
  * tick_init_highres - switch to high resolution mode
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d3f1ef4d5cbe..2aff39c6f10c 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -349,7 +349,7 @@ void tick_nohz_stop_sched_tick(int inidle)
 
                 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
                         hrtimer_start(&ts->sched_timer, expires,
-                                      HRTIMER_MODE_ABS);
+                                      HRTIMER_MODE_ABS_PINNED);
                         /* Check, if the timer was already in the past */
                         if (hrtimer_active(&ts->sched_timer))
                                 goto out;
@@ -395,7 +395,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
 
                 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
                         hrtimer_start_expires(&ts->sched_timer,
-                                      HRTIMER_MODE_ABS);
+                                              HRTIMER_MODE_ABS_PINNED);
                         /* Check, if the timer was already in the past */
                         if (hrtimer_active(&ts->sched_timer))
                                 break;
@@ -698,7 +698,8 @@ void tick_setup_sched_timer(void)
 
         for (;;) {
                 hrtimer_forward(&ts->sched_timer, now, tick_period);
-                hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS);
+                hrtimer_start_expires(&ts->sched_timer,
+                                      HRTIMER_MODE_ABS_PINNED);
                 /* Check, if the timer was already in the past */
                 if (hrtimer_active(&ts->sched_timer))
                         break;
diff --git a/kernel/timer.c b/kernel/timer.c
index faf2db897de4..54d3912f8cad 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -38,6 +38,7 @@
 #include <linux/tick.h>
 #include <linux/kallsyms.h>
 #include <linux/perf_counter.h>
+#include <linux/sched.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -605,13 +606,12 @@ static struct tvec_base *lock_timer_base(struct timer_list *timer,
 }
 
 static inline int
-__mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
+__mod_timer(struct timer_list *timer, unsigned long expires,
+                                                bool pending_only, int pinned)
 {
         struct tvec_base *base, *new_base;
         unsigned long flags;
-        int ret;
-
-        ret = 0;
+        int ret = 0 , cpu;
 
         timer_stats_timer_set_start_info(timer);
         BUG_ON(!timer->function);
@@ -630,6 +630,18 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
 
         new_base = __get_cpu_var(tvec_bases);
 
+        cpu = smp_processor_id();
+
+#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
+        if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu)) {
+                int preferred_cpu = get_nohz_load_balancer();
+
+                if (preferred_cpu >= 0)
+                        cpu = preferred_cpu;
+        }
+#endif
+        new_base = per_cpu(tvec_bases, cpu);
+
         if (base != new_base) {
                 /*
                  * We are trying to schedule the timer on the local CPU.
@@ -669,7 +681,7 @@ out_unlock:
  */
 int mod_timer_pending(struct timer_list *timer, unsigned long expires)
 {
-        return __mod_timer(timer, expires, true);
+        return __mod_timer(timer, expires, true, TIMER_NOT_PINNED);
 }
 EXPORT_SYMBOL(mod_timer_pending);
 
@@ -703,11 +715,33 @@ int mod_timer(struct timer_list *timer, unsigned long expires)
         if (timer->expires == expires && timer_pending(timer))
                 return 1;
 
-        return __mod_timer(timer, expires, false);
+        return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
 }
 EXPORT_SYMBOL(mod_timer);
 
 /**
+ * mod_timer_pinned - modify a timer's timeout
+ * @timer: the timer to be modified
+ * @expires: new timeout in jiffies
+ *
+ * mod_timer_pinned() is a way to update the expire field of an
+ * active timer (if the timer is inactive it will be activated)
+ * and not allow the timer to be migrated to a different CPU.
+ *
+ * mod_timer_pinned(timer, expires) is equivalent to:
+ *
+ *     del_timer(timer); timer->expires = expires; add_timer(timer);
+ */
+int mod_timer_pinned(struct timer_list *timer, unsigned long expires)
+{
+        if (timer->expires == expires && timer_pending(timer))
+                return 1;
+
+        return __mod_timer(timer, expires, false, TIMER_PINNED);
+}
+EXPORT_SYMBOL(mod_timer_pinned);
+
+/**
  * add_timer - start a timer
  * @timer: the timer to be added
  *
@@ -1017,6 +1051,9 @@ cascade:
                 index = slot = timer_jiffies & TVN_MASK;
                 do {
                         list_for_each_entry(nte, varp->vec + slot, entry) {
+                                if (tbase_get_deferrable(nte->base))
+                                        continue;
+
                                 found = 1;
                                 if (time_before(nte->expires, expires))
                                         expires = nte->expires;
@@ -1307,7 +1344,7 @@ signed long __sched schedule_timeout(signed long timeout)
         expire = timeout + jiffies;
 
         setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
-        __mod_timer(&timer, expire, false);
+        __mod_timer(&timer, expire, false, TIMER_NOT_PINNED);
         schedule();
         del_singleshot_timer_sync(&timer);
 
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 4a13e5a01ce3..61071fecc82e 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -147,7 +147,7 @@ config IRQSOFF_TRACER
           disabled by default and can be runtime (re-)started
           via:
 
-              echo 0 > /debugfs/tracing/tracing_max_latency
+              echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
 
           (Note that kernel size and overhead increases with this option
           enabled. This option and the preempt-off timing option can be
@@ -168,7 +168,7 @@ config PREEMPT_TRACER
           disabled by default and can be runtime (re-)started
           via:
 
-              echo 0 > /debugfs/tracing/tracing_max_latency
+              echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
 
           (Note that kernel size and overhead increases with this option
           enabled. This option and the irqs-off timing option can be
@@ -261,7 +261,7 @@ config PROFILE_ANNOTATED_BRANCHES
           This tracer profiles all the the likely and unlikely macros
           in the kernel. It will display the results in:
 
-          /debugfs/tracing/profile_annotated_branch
+          /sys/kernel/debug/tracing/profile_annotated_branch
 
           Note: this will add a significant overhead, only turn this
           on if you need to profile the system's use of these macros.
@@ -274,7 +274,7 @@ config PROFILE_ALL_BRANCHES
           taken in the kernel is recorded whether it hit or miss.
           The results will be displayed in:
 
-          /debugfs/tracing/profile_branch
+          /sys/kernel/debug/tracing/profile_branch
 
           This option also enables the likely/unlikely profiler.
 
@@ -323,7 +323,7 @@ config STACK_TRACER
         select KALLSYMS
         help
           This special tracer records the maximum stack footprint of the
-          kernel and displays it in debugfs/tracing/stack_trace.
+          kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
 
           This tracer works by hooking into every function call that the
           kernel executes, and keeping a maximum stack depth value and
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8acd9b81a5d7..c1878bfb2e1e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -344,7 +344,7 @@ static raw_spinlock_t ftrace_max_lock =
 /*
  * Copy the new maximum trace into the separate maximum-trace
  * structure. (this way the maximum trace is permanently saved,
- * for later retrieval via /debugfs/tracing/latency_trace)
+ * for later retrieval via /sys/kernel/debug/tracing/latency_trace)
  */
 static void
 __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
@@ -2414,21 +2414,20 @@ static const struct file_operations tracing_iter_fops = {
 
 static const char readme_msg[] =
         "tracing mini-HOWTO:\n\n"
-        "# mkdir /debug\n"
-        "# mount -t debugfs nodev /debug\n\n"
-        "# cat /debug/tracing/available_tracers\n"
+        "# mount -t debugfs nodev /sys/kernel/debug\n\n"
+        "# cat /sys/kernel/debug/tracing/available_tracers\n"
         "wakeup preemptirqsoff preemptoff irqsoff function sched_switch nop\n\n"
-        "# cat /debug/tracing/current_tracer\n"
+        "# cat /sys/kernel/debug/tracing/current_tracer\n"
         "nop\n"
-        "# echo sched_switch > /debug/tracing/current_tracer\n"
-        "# cat /debug/tracing/current_tracer\n"
+        "# echo sched_switch > /sys/kernel/debug/tracing/current_tracer\n"
+        "# cat /sys/kernel/debug/tracing/current_tracer\n"
         "sched_switch\n"
-        "# cat /debug/tracing/trace_options\n"
+        "# cat /sys/kernel/debug/tracing/trace_options\n"
         "noprint-parent nosym-offset nosym-addr noverbose\n"
-        "# echo print-parent > /debug/tracing/trace_options\n"
-        "# echo 1 > /debug/tracing/tracing_enabled\n"
-        "# cat /debug/tracing/trace > /tmp/trace.txt\n"
-        "# echo 0 > /debug/tracing/tracing_enabled\n"
+        "# echo print-parent > /sys/kernel/debug/tracing/trace_options\n"
+        "# echo 1 > /sys/kernel/debug/tracing/tracing_enabled\n"
+        "# cat /sys/kernel/debug/tracing/trace > /tmp/trace.txt\n"
+        "# echo 0 > /sys/kernel/debug/tracing/tracing_enabled\n"
 ;
 
 static ssize_t
diff --git a/kernel/trace/trace_sysprof.c b/kernel/trace/trace_sysprof.c
index e04b76cc238a..f6693969287d 100644
--- a/kernel/trace/trace_sysprof.c
+++ b/kernel/trace/trace_sysprof.c
@@ -203,7 +203,8 @@ static void start_stack_timer(void *unused)
         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
         hrtimer->function = stack_trace_timer_fn;
 
-        hrtimer_start(hrtimer, ns_to_ktime(sample_period), HRTIMER_MODE_REL);
+        hrtimer_start(hrtimer, ns_to_ktime(sample_period),
+                      HRTIMER_MODE_REL_PINNED);
 }
 
 static void start_stack_timers(void)
diff --git a/kernel/user.c b/kernel/user.c
index 850e0ba41c1e..2c000e7132ac 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -75,21 +75,6 @@ static void uid_hash_remove(struct user_struct *up)
         put_user_ns(up->user_ns);
 }
 
-static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
-{
-        struct user_struct *user;
-        struct hlist_node *h;
-
-        hlist_for_each_entry(user, h, hashent, uidhash_node) {
-                if (user->uid == uid) {
-                        atomic_inc(&user->__count);
-                        return user;
-                }
-        }
-
-        return NULL;
-}
-
 #ifdef CONFIG_USER_SCHED
 
 static void sched_destroy_user(struct user_struct *up)
@@ -119,6 +104,23 @@ static int sched_create_user(struct user_struct *up) { return 0; }
 
 #if defined(CONFIG_USER_SCHED) && defined(CONFIG_SYSFS)
 
+static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
+{
+        struct user_struct *user;
+        struct hlist_node *h;
+
+        hlist_for_each_entry(user, h, hashent, uidhash_node) {
+                if (user->uid == uid) {
+                        /* possibly resurrect an "almost deleted" object */
+                        if (atomic_inc_return(&user->__count) == 1)
+                                cancel_delayed_work(&user->work);
+                        return user;
+                }
+        }
+
+        return NULL;
+}
+
 static struct kset *uids_kset; /* represents the /sys/kernel/uids/ directory */
 static DEFINE_MUTEX(uids_mutex);
 
@@ -283,12 +285,12 @@ int __init uids_sysfs_init(void)
         return uids_user_create(&root_user);
 }
 
-/* work function to remove sysfs directory for a user and free up
+/* delayed work function to remove sysfs directory for a user and free up
  * corresponding structures.
  */
 static void cleanup_user_struct(struct work_struct *w)
 {
-        struct user_struct *up = container_of(w, struct user_struct, work);
+        struct user_struct *up = container_of(w, struct user_struct, work.work);
         unsigned long flags;
         int remove_user = 0;
 
@@ -297,15 +299,12 @@ static void cleanup_user_struct(struct work_struct *w)
          */
         uids_mutex_lock();
 
-        local_irq_save(flags);
-
-        if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
+        spin_lock_irqsave(&uidhash_lock, flags);
+        if (atomic_read(&up->__count) == 0) {
                 uid_hash_remove(up);
                 remove_user = 1;
-                spin_unlock_irqrestore(&uidhash_lock, flags);
-        } else {
-                local_irq_restore(flags);
         }
+        spin_unlock_irqrestore(&uidhash_lock, flags);
 
         if (!remove_user)
                 goto done;
@@ -331,16 +330,28 @@ done:
  */
 static void free_user(struct user_struct *up, unsigned long flags)
 {
-        /* restore back the count */
-        atomic_inc(&up->__count);
         spin_unlock_irqrestore(&uidhash_lock, flags);
-
-        INIT_WORK(&up->work, cleanup_user_struct);
-        schedule_work(&up->work);
+        INIT_DELAYED_WORK(&up->work, cleanup_user_struct);
+        schedule_delayed_work(&up->work, msecs_to_jiffies(1000));
 }
 
 #else   /* CONFIG_USER_SCHED && CONFIG_SYSFS */
 
+static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
+{
+        struct user_struct *user;
+        struct hlist_node *h;
+
+        hlist_for_each_entry(user, h, hashent, uidhash_node) {
+                if (user->uid == uid) {
+                        atomic_inc(&user->__count);
+                        return user;
+                }
+        }
+
+        return NULL;
+}
+
 int uids_sysfs_init(void) { return 0; }
 static inline int uids_user_create(struct user_struct *up) { return 0; }
 static inline void uids_mutex_lock(void) { }