19 files changed, 145 insertions, 102 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 794c862125fe..0672ff88f159 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -247,6 +247,7 @@ again:
         if (err < 0)
                 return err;
 
+        page = compound_head(page);
         lock_page(page);
         if (!page->mapping) {
                 unlock_page(page);
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 9002958a96e7..49da79ab8486 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -191,6 +191,46 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
         }
 }
 
+
+/*
+ * Get the preferred target CPU for NOHZ
+ */
+static int hrtimer_get_target(int this_cpu, int pinned)
+{
+#ifdef CONFIG_NO_HZ
+        if (!pinned && get_sysctl_timer_migration() && idle_cpu(this_cpu)) {
+                int preferred_cpu = get_nohz_load_balancer();
+
+                if (preferred_cpu >= 0)
+                        return preferred_cpu;
+        }
+#endif
+        return this_cpu;
+}
+
+/*
+ * With HIGHRES=y 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.
+ *
+ * Called with cpu_base->lock of target cpu held.
+ */
+static int
+hrtimer_check_target(struct hrtimer *timer, struct hrtimer_clock_base *new_base)
+{
+#ifdef CONFIG_HIGH_RES_TIMERS
+        ktime_t expires;
+
+        if (!new_base->cpu_base->hres_active)
+                return 0;
+
+        expires = ktime_sub(hrtimer_get_expires(timer), new_base->offset);
+        return expires.tv64 <= new_base->cpu_base->expires_next.tv64;
+#else
+        return 0;
+#endif
+}
+
 /*
  * Switch the timer base to the current CPU when possible.
  */
@@ -200,16 +240,8 @@ switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
 {
         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
+        int this_cpu = smp_processor_id();
+        int cpu = hrtimer_get_target(this_cpu, pinned);
 
 again:
         new_cpu_base = &per_cpu(hrtimer_bases, cpu);
@@ -217,7 +249,7 @@ again:
 
         if (base != new_base) {
                 /*
-                 * We are trying to schedule the timer on the local CPU.
+                 * We are trying to move timer to new_base.
                  * However we can't change timer's base while it is running,
                  * so we keep it on the same CPU. No hassle vs. reprogramming
                  * the event source in the high resolution case. The softirq
@@ -233,38 +265,12 @@ again:
                 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;
-                        }
+                if (cpu != this_cpu && hrtimer_check_target(timer, new_base)) {
+                        cpu = this_cpu;
+                        spin_unlock(&new_base->cpu_base->lock);
+                        spin_lock(&base->cpu_base->lock);
+                        timer->base = base;
+                        goto again;
                 }
                 timer->base = new_base;
         }
@@ -1276,14 +1282,22 @@ void hrtimer_interrupt(struct clock_event_device *dev)
 
         expires_next.tv64 = KTIME_MAX;
 
+        spin_lock(&cpu_base->lock);
+        /*
+         * We set expires_next to KTIME_MAX here with cpu_base->lock
+         * held to prevent that a timer is enqueued in our queue via
+         * the migration code. This does not affect enqueueing of
+         * timers which run their callback and need to be requeued on
+         * this CPU.
+         */
+        cpu_base->expires_next.tv64 = KTIME_MAX;
+
         base = cpu_base->clock_base;
 
         for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
                 ktime_t basenow;
                 struct rb_node *node;
 
-                spin_lock(&cpu_base->lock);
-
                 basenow = ktime_add(now, base->offset);
 
                 while ((node = base->first)) {
@@ -1316,11 +1330,15 @@ void hrtimer_interrupt(struct clock_event_device *dev)
 
                         __run_hrtimer(timer);
                 }
-                spin_unlock(&cpu_base->lock);
                 base++;
         }
 
+        /*
+         * Store the new expiry value so the migration code can verify
+         * against it.
+         */
         cpu_base->expires_next = expires_next;
+        spin_unlock(&cpu_base->lock);
 
         /* Reprogramming necessary ? */
         if (expires_next.tv64 != KTIME_MAX) {
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index c0fa54b276d9..16b5739c516a 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -237,13 +237,9 @@ static int __kprobes collect_garbage_slots(void)
 {
         struct kprobe_insn_page *kip;
         struct hlist_node *pos, *next;
-        int safety;
 
         /* Ensure no-one is preepmted on the garbages */
-        mutex_unlock(&kprobe_insn_mutex);
-        safety = check_safety();
-        mutex_lock(&kprobe_insn_mutex);
-        if (safety != 0)
+        if (check_safety())
                 return -EAGAIN;
 
         hlist_for_each_entry_safe(kip, pos, next, &kprobe_insn_pages, hlist) {
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index a641eb753b8c..7bc888dfd06a 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -2665,6 +2665,7 @@ static void perf_counter_output(struct perf_counter *counter, int nmi,
                 header.size += sizeof(cpu_entry);
 
                 cpu_entry.cpu = raw_smp_processor_id();
+                cpu_entry.reserved = 0;
         }
 
         if (sample_type & PERF_SAMPLE_PERIOD)
diff --git a/kernel/pid.c b/kernel/pid.c
index 5fa1db48d8b7..31310b5d3f50 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -36,7 +36,6 @@
 #include <linux/pid_namespace.h>
 #include <linux/init_task.h>
 #include <linux/syscalls.h>
-#include <linux/kmemleak.h>
 
 #define pid_hashfn(nr, ns)      \
         hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
@@ -513,12 +512,6 @@ void __init pidhash_init(void)
         pid_hash = alloc_bootmem(pidhash_size * sizeof(*(pid_hash)));
         if (!pid_hash)
                 panic("Could not alloc pidhash!\n");
-        /*
-         * pid_hash contains references to allocated struct pid objects and it
-         * must be scanned by kmemleak to avoid false positives.
-         */
-        kmemleak_alloc(pid_hash, pidhash_size * sizeof(*(pid_hash)), 0,
-                       GFP_KERNEL);
         for (i = 0; i < pidhash_size; i++)
                 INIT_HLIST_HEAD(&pid_hash[i]);
 }
diff --git a/kernel/power/user.c b/kernel/power/user.c
index ed97375daae9..bf0014d6a5f0 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -23,7 +23,6 @@
 #include <linux/console.h>
 #include <linux/cpu.h>
 #include <linux/freezer.h>
-#include <linux/smp_lock.h>
 #include <scsi/scsi_scan.h>
 
 #include <asm/uaccess.h>
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 0dccfbba6d26..7717b95c2027 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1533,7 +1533,7 @@ void __init __rcu_init(void)
         int j;
         struct rcu_node *rnp;
 
-        printk(KERN_WARNING "Experimental hierarchical RCU implementation.\n");
+        printk(KERN_INFO "Hierarchical RCU implementation.\n");
 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
         printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n");
 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
@@ -1546,7 +1546,6 @@ void __init __rcu_init(void)
                 rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long)i);
         /* Register notifier for non-boot CPUs */
         register_cpu_notifier(&rcu_nb);
-        printk(KERN_WARNING "Experimental hierarchical RCU init done.\n");
 }
 
 module_param(blimit, int, 0);
diff --git a/kernel/sched.c b/kernel/sched.c
index 7c9098d186e6..98972d366fdc 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -493,6 +493,7 @@ struct rt_rq {
 #endif
 #ifdef CONFIG_SMP
         unsigned long rt_nr_migratory;
+        unsigned long rt_nr_total;
         int overloaded;
         struct plist_head pushable_tasks;
 #endif
@@ -2571,15 +2572,37 @@ static void __sched_fork(struct task_struct *p)
         p->se.avg_wakeup                = sysctl_sched_wakeup_granularity;
 
 #ifdef CONFIG_SCHEDSTATS
-        p->se.wait_start                = 0;
-        p->se.sum_sleep_runtime         = 0;
-        p->se.sleep_start               = 0;
-        p->se.block_start               = 0;
-        p->se.sleep_max                 = 0;
-        p->se.block_max                 = 0;
-        p->se.exec_max                  = 0;
-        p->se.slice_max                 = 0;
-        p->se.wait_max                  = 0;
+        p->se.wait_start                        = 0;
+        p->se.wait_max                          = 0;
+        p->se.wait_count                        = 0;
+        p->se.wait_sum                          = 0;
+
+        p->se.sleep_start                       = 0;
+        p->se.sleep_max                         = 0;
+        p->se.sum_sleep_runtime                 = 0;
+
+        p->se.block_start                       = 0;
+        p->se.block_max                         = 0;
+        p->se.exec_max                          = 0;
+        p->se.slice_max                         = 0;
+
+        p->se.nr_migrations_cold                = 0;
+        p->se.nr_failed_migrations_affine       = 0;
+        p->se.nr_failed_migrations_running      = 0;
+        p->se.nr_failed_migrations_hot          = 0;
+        p->se.nr_forced_migrations              = 0;
+        p->se.nr_forced2_migrations             = 0;
+
+        p->se.nr_wakeups                        = 0;
+        p->se.nr_wakeups_sync                   = 0;
+        p->se.nr_wakeups_migrate                = 0;
+        p->se.nr_wakeups_local                  = 0;
+        p->se.nr_wakeups_remote                 = 0;
+        p->se.nr_wakeups_affine                 = 0;
+        p->se.nr_wakeups_affine_attempts        = 0;
+        p->se.nr_wakeups_passive                = 0;
+        p->se.nr_wakeups_idle                   = 0;
+
 #endif
 
         INIT_LIST_HEAD(&p->rt.run_list);
@@ -6541,6 +6564,11 @@ SYSCALL_DEFINE0(sched_yield)
         return 0;
 }
 
+static inline int should_resched(void)
+{
+        return need_resched() && !(preempt_count() & PREEMPT_ACTIVE);
+}
+
 static void __cond_resched(void)
 {
 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
@@ -6560,8 +6588,7 @@ static void __cond_resched(void)
 
 int __sched _cond_resched(void)
 {
-        if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) &&
-                                        system_state == SYSTEM_RUNNING) {
+        if (should_resched()) {
                 __cond_resched();
                 return 1;
         }
@@ -6579,12 +6606,12 @@ EXPORT_SYMBOL(_cond_resched);
  */
 int cond_resched_lock(spinlock_t *lock)
 {
-        int resched = need_resched() && system_state == SYSTEM_RUNNING;
+        int resched = should_resched();
         int ret = 0;
 
         if (spin_needbreak(lock) || resched) {
                 spin_unlock(lock);
-                if (resched && need_resched())
+                if (resched)
                         __cond_resched();
                 else
                         cpu_relax();
@@ -6599,7 +6626,7 @@ int __sched cond_resched_softirq(void)
 {
         BUG_ON(!in_softirq());
 
-        if (need_resched() && system_state == SYSTEM_RUNNING) {
+        if (should_resched()) {
                 local_bh_enable();
                 __cond_resched();
                 local_bh_disable();
@@ -9070,7 +9097,7 @@ static void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)
 #ifdef CONFIG_SMP
         rt_rq->rt_nr_migratory = 0;
         rt_rq->overloaded = 0;
-        plist_head_init(&rq->rt.pushable_tasks, &rq->lock);
+        plist_head_init(&rt_rq->pushable_tasks, &rq->lock);
 #endif
 
         rt_rq->rt_time = 0;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index ba7fd6e9556f..7c248dc30f41 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -687,7 +687,8 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
                          * all of which have the same weight.
                          */
                         if (sched_feat(NORMALIZED_SLEEPER) &&
-                                        task_of(se)->policy != SCHED_IDLE)
+                                        (!entity_is_task(se) ||
+                                         task_of(se)->policy != SCHED_IDLE))
                                 thresh = calc_delta_fair(thresh, se);
 
                         vruntime -= thresh;
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 9bf0d2a73045..3918e01994e0 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -10,6 +10,8 @@ static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
 
 #ifdef CONFIG_RT_GROUP_SCHED
 
+#define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
+
 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 {
         return rt_rq->rq;
@@ -22,6 +24,8 @@ static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
 
 #else /* CONFIG_RT_GROUP_SCHED */
 
+#define rt_entity_is_task(rt_se) (1)
+
 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 {
         return container_of(rt_rq, struct rq, rt);
@@ -73,7 +77,7 @@ static inline void rt_clear_overload(struct rq *rq)
 
 static void update_rt_migration(struct rt_rq *rt_rq)
 {
-        if (rt_rq->rt_nr_migratory && (rt_rq->rt_nr_running > 1)) {
+        if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
                 if (!rt_rq->overloaded) {
                         rt_set_overload(rq_of_rt_rq(rt_rq));
                         rt_rq->overloaded = 1;
@@ -86,6 +90,12 @@ static void update_rt_migration(struct rt_rq *rt_rq)
 
 static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 {
+        if (!rt_entity_is_task(rt_se))
+                return;
+
+        rt_rq = &rq_of_rt_rq(rt_rq)->rt;
+
+        rt_rq->rt_nr_total++;
         if (rt_se->nr_cpus_allowed > 1)
                 rt_rq->rt_nr_migratory++;
 
@@ -94,6 +104,12 @@ static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 
 static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 {
+        if (!rt_entity_is_task(rt_se))
+                return;
+
+        rt_rq = &rq_of_rt_rq(rt_rq)->rt;
+
+        rt_rq->rt_nr_total--;
         if (rt_se->nr_cpus_allowed > 1)
                 rt_rq->rt_nr_migratory--;
 
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 1ad6dd461119..a6dcd67b041d 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -254,15 +254,4 @@ 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/trace/Kconfig b/kernel/trace/Kconfig
index 1551f47e7669..019f380fd764 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -226,13 +226,13 @@ config BOOT_TRACER
           the timings of the initcalls and traces key events and the identity
           of tasks that can cause boot delays, such as context-switches.
 
-          Its aim is to be parsed by the /scripts/bootgraph.pl tool to
+          Its aim is to be parsed by the scripts/bootgraph.pl tool to
           produce pretty graphics about boot inefficiencies, giving a visual
           representation of the delays during initcalls - but the raw
           /debug/tracing/trace text output is readable too.
 
-          You must pass in ftrace=initcall to the kernel command line
-          to enable this on bootup.
+          You must pass in initcall_debug and ftrace=initcall to the kernel
+          command line to enable this on bootup.
 
 config TRACE_BRANCH_PROFILING
         bool
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 39af8af6fc30..1090b0aed9ba 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -22,6 +22,7 @@
 #include <linux/init.h>
 #include <linux/mutex.h>
 #include <linux/debugfs.h>
+#include <linux/smp_lock.h>
 #include <linux/time.h>
 #include <linux/uaccess.h>
 
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f3716bf04df6..4521c77d1a1a 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -768,7 +768,7 @@ static struct tracer_stat function_stats __initdata = {
         .stat_show      = function_stat_show
 };
 
-static void ftrace_profile_debugfs(struct dentry *d_tracer)
+static __init void ftrace_profile_debugfs(struct dentry *d_tracer)
 {
         struct ftrace_profile_stat *stat;
         struct dentry *entry;
@@ -786,7 +786,6 @@ static void ftrace_profile_debugfs(struct dentry *d_tracer)
                          * The files created are permanent, if something happens
                          * we still do not free memory.
                          */
-                        kfree(stat);
                         WARN(1,
                              "Could not allocate stat file for cpu %d\n",
                              cpu);
@@ -813,7 +812,7 @@ static void ftrace_profile_debugfs(struct dentry *d_tracer)
 }
 
 #else /* CONFIG_FUNCTION_PROFILER */
-static void ftrace_profile_debugfs(struct dentry *d_tracer)
+static __init void ftrace_profile_debugfs(struct dentry *d_tracer)
 {
 }
 #endif /* CONFIG_FUNCTION_PROFILER */
@@ -3160,10 +3159,10 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 
         ret  = proc_dointvec(table, write, file, buffer, lenp, ppos);
 
-        if (ret || !write || (last_ftrace_enabled == ftrace_enabled))
+        if (ret || !write || (last_ftrace_enabled == !!ftrace_enabled))
                 goto out;
 
-        last_ftrace_enabled = ftrace_enabled;
+        last_ftrace_enabled = !!ftrace_enabled;
 
         if (ftrace_enabled) {
 
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 3aa0a0dfdfa8..8bc8d8afea6a 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -17,6 +17,7 @@
 #include <linux/writeback.h>
 #include <linux/kallsyms.h>
 #include <linux/seq_file.h>
+#include <linux/smp_lock.h>
 #include <linux/notifier.h>
 #include <linux/irqflags.h>
 #include <linux/debugfs.h>
diff --git a/kernel/trace/trace_event_types.h b/kernel/trace/trace_event_types.h
index 5e32e375134d..6db005e12487 100644
--- a/kernel/trace/trace_event_types.h
+++ b/kernel/trace/trace_event_types.h
@@ -26,6 +26,9 @@ TRACE_EVENT_FORMAT(funcgraph_exit, TRACE_GRAPH_RET,
                    ftrace_graph_ret_entry, ignore,
         TRACE_STRUCT(
                 TRACE_FIELD(unsigned long, ret.func, func)
+                TRACE_FIELD(unsigned long long, ret.calltime, calltime)
+                TRACE_FIELD(unsigned long long, ret.rettime, rettime)
+                TRACE_FIELD(unsigned long, ret.overrun, overrun)
                 TRACE_FIELD(int, ret.depth, depth)
         ),
         TP_RAW_FMT("<-- %lx (%d)")
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 7402144bff21..75ef000613c3 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -363,7 +363,7 @@ ftrace_trace_onoff_callback(char *glob, char *cmd, char *param, int enable)
  out_reg:
         ret = register_ftrace_function_probe(glob, ops, count);
 
-        return ret;
+        return ret < 0 ? ret : 0;
 }
 
 static struct ftrace_func_command ftrace_traceon_cmd = {
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 7938f3ae93e3..e0c2545622e8 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -27,8 +27,7 @@ void trace_print_seq(struct seq_file *m, struct trace_seq *s)
 {
         int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
 
-        s->buffer[len] = 0;
-        seq_puts(m, s->buffer);
+        seq_write(m, s->buffer, len);
 
         trace_seq_init(s);
 }
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 2d7aebd71dbd..e644af910124 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -326,10 +326,10 @@ stack_trace_sysctl(struct ctl_table *table, int write,
         ret = proc_dointvec(table, write, file, buffer, lenp, ppos);
 
         if (ret || !write ||
-            (last_stack_tracer_enabled == stack_tracer_enabled))
+            (last_stack_tracer_enabled == !!stack_tracer_enabled))
                 goto out;
 
-        last_stack_tracer_enabled = stack_tracer_enabled;
+        last_stack_tracer_enabled = !!stack_tracer_enabled;
 
         if (stack_tracer_enabled)
                 register_ftrace_function(&trace_ops);