Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

16 files changed, 326 insertions, 143 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7dc8788cfd52..940aced4ed00 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1035,6 +1035,11 @@ static void cgroup_get(struct cgroup *cgrp)
         css_get(&cgrp->self);
 }
 
+static bool cgroup_tryget(struct cgroup *cgrp)
+{
+        return css_tryget(&cgrp->self);
+}
+
 static void cgroup_put(struct cgroup *cgrp)
 {
         css_put(&cgrp->self);
@@ -1147,7 +1152,8 @@ static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn)
          * protection against removal.  Ensure @cgrp stays accessible and
          * break the active_ref protection.
          */
-        cgroup_get(cgrp);
+        if (!cgroup_tryget(cgrp))
+                return NULL;
         kernfs_break_active_protection(kn);
 
         mutex_lock(&cgroup_mutex);
@@ -3271,8 +3277,17 @@ int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 {
         struct cftype *cft;
 
-        for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
-                cft->flags |= __CFTYPE_NOT_ON_DFL;
+        /*
+         * If legacy_flies_on_dfl, we want to show the legacy files on the
+         * dfl hierarchy but iff the target subsystem hasn't been updated
+         * for the dfl hierarchy yet.
+         */
+        if (!cgroup_legacy_files_on_dfl ||
+            ss->dfl_cftypes != ss->legacy_cftypes) {
+                for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
+                        cft->flags |= __CFTYPE_NOT_ON_DFL;
+        }
+
         return cgroup_add_cftypes(ss, cfts);
 }
 
@@ -4387,6 +4402,15 @@ static void css_release_work_fn(struct work_struct *work)
                 /* cgroup release path */
                 cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
                 cgrp->id = -1;
+
+                /*
+                 * There are two control paths which try to determine
+                 * cgroup from dentry without going through kernfs -
+                 * cgroupstats_build() and css_tryget_online_from_dir().
+                 * Those are supported by RCU protecting clearing of
+                 * cgrp->kn->priv backpointer.
+                 */
+                RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL);
         }
 
         mutex_unlock(&cgroup_mutex);
@@ -4543,6 +4567,11 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
         struct cftype *base_files;
         int ssid, ret;
 
+        /* Do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable.
+         */
+        if (strchr(name, '\n'))
+                return -EINVAL;
+
         parent = cgroup_kn_lock_live(parent_kn);
         if (!parent)
                 return -ENODEV;
@@ -4820,16 +4849,6 @@ static int cgroup_rmdir(struct kernfs_node *kn)
 
         cgroup_kn_unlock(kn);
 
-        /*
-         * There are two control paths which try to determine cgroup from
-         * dentry without going through kernfs - cgroupstats_build() and
-         * css_tryget_online_from_dir().  Those are supported by RCU
-         * protecting clearing of cgrp->kn->priv backpointer, which should
-         * happen after all files under it have been removed.
-         */
-        if (!ret)
-                RCU_INIT_POINTER(*(void __rcu __force **)&kn->priv, NULL);
-
         cgroup_put(cgrp);
         return ret;
 }
@@ -5416,7 +5435,7 @@ struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
         /*
          * This path doesn't originate from kernfs and @kn could already
          * have been or be removed at any point.  @kn->priv is RCU
-         * protected for this access.  See cgroup_rmdir() for details.
+         * protected for this access.  See css_release_work_fn() for details.
          */
         cgrp = rcu_dereference(kn->priv);
         if (cgrp)
diff --git a/kernel/compat.c b/kernel/compat.c
index 633394f442f8..ebb3c369d03d 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -226,7 +226,7 @@ static long compat_nanosleep_restart(struct restart_block *restart)
         ret = hrtimer_nanosleep_restart(restart);
         set_fs(oldfs);
 
-        if (ret) {
+        if (ret == -ERESTART_RESTARTBLOCK) {
                 rmtp = restart->nanosleep.compat_rmtp;
 
                 if (rmtp && compat_put_timespec(&rmt, rmtp))
@@ -256,7 +256,26 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp,
                                 HRTIMER_MODE_REL, CLOCK_MONOTONIC);
         set_fs(oldfs);
 
-        if (ret) {
+        /*
+         * hrtimer_nanosleep() can only return 0 or
+         * -ERESTART_RESTARTBLOCK here because:
+         *
+         * - we call it with HRTIMER_MODE_REL and therefor exclude the
+         *   -ERESTARTNOHAND return path.
+         *
+         * - we supply the rmtp argument from the task stack (due to
+         *   the necessary compat conversion. So the update cannot
+         *   fail, which excludes the -EFAULT return path as well. If
+         *   it fails nevertheless we have a bigger problem and wont
+         *   reach this place anymore.
+         *
+         * - if the return value is 0, we do not have to update rmtp
+         *    because there is no remaining time.
+         *
+         * We check for -ERESTART_RESTARTBLOCK nevertheless if the
+         * core implementation decides to return random nonsense.
+         */
+        if (ret == -ERESTART_RESTARTBLOCK) {
                 struct restart_block *restart
                         = &current_thread_info()->restart_block;
 
@@ -266,7 +285,6 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp,
                 if (rmtp && compat_put_timespec(&rmt, rmtp))
                         return -EFAULT;
         }
-
         return ret;
 }
 
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1cf24b3e42ec..f9c1ed002dbc 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -41,6 +41,7 @@
 #include <linux/cgroup.h>
 #include <linux/module.h>
 #include <linux/mman.h>
+#include <linux/compat.h>
 
 #include "internal.h"
 
@@ -3717,6 +3718,26 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
         return 0;
 }
 
+#ifdef CONFIG_COMPAT
+static long perf_compat_ioctl(struct file *file, unsigned int cmd,
+                                unsigned long arg)
+{
+        switch (_IOC_NR(cmd)) {
+        case _IOC_NR(PERF_EVENT_IOC_SET_FILTER):
+        case _IOC_NR(PERF_EVENT_IOC_ID):
+                /* Fix up pointer size (usually 4 -> 8 in 32-on-64-bit case */
+                if (_IOC_SIZE(cmd) == sizeof(compat_uptr_t)) {
+                        cmd &= ~IOCSIZE_MASK;
+                        cmd |= sizeof(void *) << IOCSIZE_SHIFT;
+                }
+                break;
+        }
+        return perf_ioctl(file, cmd, arg);
+}
+#else
+# define perf_compat_ioctl NULL
+#endif
+
 int perf_event_task_enable(void)
 {
         struct perf_event *event;
@@ -4222,7 +4243,7 @@ static const struct file_operations perf_fops = {
         .read                   = perf_read,
         .poll                   = perf_poll,
         .unlocked_ioctl         = perf_ioctl,
-        .compat_ioctl           = perf_ioctl,
+        .compat_ioctl           = perf_compat_ioctl,
         .mmap                   = perf_mmap,
         .fasync                 = perf_fasync,
 };
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index a2b28a2fd7b1..6223fab9a9d2 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -517,6 +517,7 @@ out:
                 chip->irq_eoi(&desc->irq_data);
         raw_spin_unlock(&desc->lock);
 }
+EXPORT_SYMBOL_GPL(handle_fasteoi_irq);
 
 /**
  *      handle_edge_irq - edge type IRQ handler
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 0b49a0a58102..2bee072268d9 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -64,7 +64,9 @@ bool kexec_in_progress = false;
 char __weak kexec_purgatory[0];
 size_t __weak kexec_purgatory_size = 0;
 
+#ifdef CONFIG_KEXEC_FILE
 static int kexec_calculate_store_digests(struct kimage *image);
+#endif
 
 /* Location of the reserved area for the crash kernel */
 struct resource crashk_res = {
@@ -341,6 +343,7 @@ out_free_image:
         return ret;
 }
 
+#ifdef CONFIG_KEXEC_FILE
 static int copy_file_from_fd(int fd, void **buf, unsigned long *buf_len)
 {
         struct fd f = fdget(fd);
@@ -612,6 +615,9 @@ out_free_image:
         kfree(image);
         return ret;
 }
+#else /* CONFIG_KEXEC_FILE */
+static inline void kimage_file_post_load_cleanup(struct kimage *image) { }
+#endif /* CONFIG_KEXEC_FILE */
 
 static int kimage_is_destination_range(struct kimage *image,
                                         unsigned long start,
@@ -1375,6 +1381,7 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 }
 #endif
 
+#ifdef CONFIG_KEXEC_FILE
 SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
                 unsigned long, cmdline_len, const char __user *, cmdline_ptr,
                 unsigned long, flags)
@@ -1451,6 +1458,8 @@ out:
         return ret;
 }
 
+#endif /* CONFIG_KEXEC_FILE */
+
 void crash_kexec(struct pt_regs *regs)
 {
         /* Take the kexec_mutex here to prevent sys_kexec_load
@@ -2006,6 +2015,7 @@ static int __init crash_save_vmcoreinfo_init(void)
 
 subsys_initcall(crash_save_vmcoreinfo_init);
 
+#ifdef CONFIG_KEXEC_FILE
 static int __kexec_add_segment(struct kimage *image, char *buf,
                                unsigned long bufsz, unsigned long mem,
                                unsigned long memsz)
@@ -2682,6 +2692,7 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name,
 
         return 0;
 }
+#endif /* CONFIG_KEXEC_FILE */
 
 /*
  * Move into place and start executing a preloaded standalone
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 734e9a7d280b..3995f546d0f3 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1778,7 +1778,18 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
         unsigned long hash, flags = 0;
         struct kretprobe_instance *ri;
 
-        /*TODO: consider to only swap the RA after the last pre_handler fired */
+        /*
+         * To avoid deadlocks, prohibit return probing in NMI contexts,
+         * just skip the probe and increase the (inexact) 'nmissed'
+         * statistical counter, so that the user is informed that
+         * something happened:
+         */
+        if (unlikely(in_nmi())) {
+                rp->nmissed++;
+                return 0;
+        }
+
+        /* TODO: consider to only swap the RA after the last pre_handler fired */
         hash = hash_ptr(current, KPROBE_HASH_BITS);
         raw_spin_lock_irqsave(&rp->lock, flags);
         if (!hlist_empty(&rp->free_instances)) {
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 5d49dcac2537..2df883a9d3cb 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -179,6 +179,7 @@ extern void swsusp_show_speed(struct timeval *, struct timeval *,
 
 #ifdef CONFIG_SUSPEND
 /* kernel/power/suspend.c */
+extern const char *pm_labels[];
 extern const char *pm_states[];
 
 extern int suspend_devices_and_enter(suspend_state_t state);
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 6dadb25cb0d8..18c62195660f 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -31,7 +31,7 @@
 
 #include "power.h"
 
-static const char *pm_labels[] = { "mem", "standby", "freeze", };
+const char *pm_labels[] = { "mem", "standby", "freeze", NULL };
 const char *pm_states[PM_SUSPEND_MAX];
 
 static const struct platform_suspend_ops *suspend_ops;
diff --git a/kernel/power/suspend_test.c b/kernel/power/suspend_test.c
index 2f524928b6aa..bd91bc177c93 100644
--- a/kernel/power/suspend_test.c
+++ b/kernel/power/suspend_test.c
@@ -129,20 +129,20 @@ static int __init has_wakealarm(struct device *dev, const void *data)
  * at startup time.  They're normally disabled, for faster boot and because
  * we can't know which states really work on this particular system.
  */
-static suspend_state_t test_state __initdata = PM_SUSPEND_ON;
+static const char *test_state_label __initdata;
 
 static char warn_bad_state[] __initdata =
         KERN_WARNING "PM: can't test '%s' suspend state\n";
 
 static int __init setup_test_suspend(char *value)
 {
-        suspend_state_t i;
+        int i;
 
         /* "=mem" ==> "mem" */
         value++;
-        for (i = PM_SUSPEND_MIN; i < PM_SUSPEND_MAX; i++)
-                if (!strcmp(pm_states[i], value)) {
-                        test_state = i;
+        for (i = 0; pm_labels[i]; i++)
+                if (!strcmp(pm_labels[i], value)) {
+                        test_state_label = pm_labels[i];
                         return 0;
                 }
 
@@ -158,13 +158,21 @@ static int __init test_suspend(void)
 
         struct rtc_device       *rtc = NULL;
         struct device           *dev;
+        suspend_state_t test_state;
 
         /* PM is initialized by now; is that state testable? */
-        if (test_state == PM_SUSPEND_ON)
-                goto done;
-        if (!pm_states[test_state]) {
-                printk(warn_bad_state, pm_states[test_state]);
-                goto done;
+        if (!test_state_label)
+                return 0;
+
+        for (test_state = PM_SUSPEND_MIN; test_state < PM_SUSPEND_MAX; test_state++) {
+                const char *state_label = pm_states[test_state];
+
+                if (state_label && !strcmp(test_state_label, state_label))
+                        break;
+        }
+        if (test_state == PM_SUSPEND_MAX) {
+                printk(warn_bad_state, test_state_label);
+                return 0;
         }
 
         /* RTCs have initialized by now too ... can we use one? */
@@ -173,13 +181,12 @@ static int __init test_suspend(void)
                 rtc = rtc_class_open(dev_name(dev));
         if (!rtc) {
                 printk(warn_no_rtc);
-                goto done;
+                return 0;
         }
 
         /* go for it */
         test_wakealarm(rtc, test_state);
         rtc_class_close(rtc);
-done:
         return 0;
 }
 late_initcall(test_suspend);
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 71e64c718f75..6a86eb7bac45 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -358,7 +358,7 @@ struct rcu_data {
         struct rcu_head **nocb_gp_tail;
         long nocb_gp_count;
         long nocb_gp_count_lazy;
-        bool nocb_leader_wake;          /* Is the nocb leader thread awake? */
+        bool nocb_leader_sleep;         /* Is the nocb leader thread asleep? */
         struct rcu_data *nocb_next_follower;
                                         /* Next follower in wakeup chain. */
 
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 00dc411e9676..a7997e272564 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2074,9 +2074,9 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force)
 
         if (!ACCESS_ONCE(rdp_leader->nocb_kthread))
                 return;
-        if (!ACCESS_ONCE(rdp_leader->nocb_leader_wake) || force) {
+        if (ACCESS_ONCE(rdp_leader->nocb_leader_sleep) || force) {
                 /* Prior xchg orders against prior callback enqueue. */
-                ACCESS_ONCE(rdp_leader->nocb_leader_wake) = true;
+                ACCESS_ONCE(rdp_leader->nocb_leader_sleep) = false;
                 wake_up(&rdp_leader->nocb_wq);
         }
 }
@@ -2253,7 +2253,7 @@ wait_again:
         if (!rcu_nocb_poll) {
                 trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep");
                 wait_event_interruptible(my_rdp->nocb_wq,
-                                         ACCESS_ONCE(my_rdp->nocb_leader_wake));
+                                !ACCESS_ONCE(my_rdp->nocb_leader_sleep));
                 /* Memory barrier handled by smp_mb() calls below and repoll. */
         } else if (firsttime) {
                 firsttime = false; /* Don't drown trace log with "Poll"! */
@@ -2292,12 +2292,12 @@ wait_again:
                 schedule_timeout_interruptible(1);
 
                 /* Rescan in case we were a victim of memory ordering. */
-                my_rdp->nocb_leader_wake = false;
-                smp_mb();  /* Ensure _wake false before scan. */
+                my_rdp->nocb_leader_sleep = true;
+                smp_mb();  /* Ensure _sleep true before scan. */
                 for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower)
                         if (ACCESS_ONCE(rdp->nocb_head)) {
                                 /* Found CB, so short-circuit next wait. */
-                                my_rdp->nocb_leader_wake = true;
+                                my_rdp->nocb_leader_sleep = false;
                                 break;
                         }
                 goto wait_again;
@@ -2307,17 +2307,17 @@ wait_again:
         rcu_nocb_wait_gp(my_rdp);
 
         /*
-         * We left ->nocb_leader_wake set to reduce cache thrashing.
-         * We clear it now, but recheck for new callbacks while
+         * We left ->nocb_leader_sleep unset to reduce cache thrashing.
+         * We set it now, but recheck for new callbacks while
          * traversing our follower list.
          */
-        my_rdp->nocb_leader_wake = false;
-        smp_mb(); /* Ensure _wake false before scan of ->nocb_head. */
+        my_rdp->nocb_leader_sleep = true;
+        smp_mb(); /* Ensure _sleep true before scan of ->nocb_head. */
 
         /* Each pass through the following loop wakes a follower, if needed. */
         for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) {
                 if (ACCESS_ONCE(rdp->nocb_head))
-                        my_rdp->nocb_leader_wake = true; /* No need to wait. */
+                        my_rdp->nocb_leader_sleep = false;/* No need to sleep.*/
                 if (!rdp->nocb_gp_head)
                         continue; /* No CBs, so no need to wake follower. */
 
diff --git a/kernel/resource.c b/kernel/resource.c
index da14b8d09296..60c5a3856ab7 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -351,15 +351,12 @@ static int find_next_iomem_res(struct resource *res, char *name,
         end = res->end;
         BUG_ON(start >= end);
 
-        read_lock(&resource_lock);
-
-        if (first_level_children_only) {
-                p = iomem_resource.child;
+        if (first_level_children_only)
                 sibling_only = true;
-        } else
-                p = &iomem_resource;
 
-        while ((p = next_resource(p, sibling_only))) {
+        read_lock(&resource_lock);
+
+        for (p = iomem_resource.child; p; p = next_resource(p, sibling_only)) {
                 if (p->flags != res->flags)
                         continue;
                 if (name && strcmp(p->name, name))
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 99aa6ee3908f..f654a8a298fa 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -225,6 +225,20 @@ static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
 };
 
 /*
+ * Kick this CPU if it's full dynticks in order to force it to
+ * re-evaluate its dependency on the tick and restart it if necessary.
+ * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(),
+ * is NMI safe.
+ */
+void tick_nohz_full_kick(void)
+{
+        if (!tick_nohz_full_cpu(smp_processor_id()))
+                return;
+
+        irq_work_queue(&__get_cpu_var(nohz_full_kick_work));
+}
+
+/*
  * Kick the CPU if it's full dynticks in order to force it to
  * re-evaluate its dependency on the tick and restart it if necessary.
  */
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index fb4a9c2cf8d9..ec1791fae965 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -442,11 +442,12 @@ static void timekeeping_update(struct timekeeper *tk, unsigned int action)
                 tk->ntp_error = 0;
                 ntp_clear();
         }
-        update_vsyscall(tk);
-        update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
 
         tk_update_ktime_data(tk);
 
+        update_vsyscall(tk);
+        update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
+
         if (action & TK_MIRROR)
                 memcpy(&shadow_timekeeper, &tk_core.timekeeper,
                        sizeof(tk_core.timekeeper));
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1654b12c891a..5916a8e59e87 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -65,15 +65,21 @@
 #define FL_GLOBAL_CONTROL_MASK (FTRACE_OPS_FL_CONTROL)
 
 #ifdef CONFIG_DYNAMIC_FTRACE
-#define INIT_REGEX_LOCK(opsname)        \
-        .regex_lock     = __MUTEX_INITIALIZER(opsname.regex_lock),
+#define INIT_OPS_HASH(opsname)  \
+        .func_hash              = &opsname.local_hash,                  \
+        .local_hash.regex_lock  = __MUTEX_INITIALIZER(opsname.local_hash.regex_lock),
+#define ASSIGN_OPS_HASH(opsname, val) \
+        .func_hash              = val, \
+        .local_hash.regex_lock  = __MUTEX_INITIALIZER(opsname.local_hash.regex_lock),
 #else
-#define INIT_REGEX_LOCK(opsname)
+#define INIT_OPS_HASH(opsname)
+#define ASSIGN_OPS_HASH(opsname, val)
 #endif
 
 static struct ftrace_ops ftrace_list_end __read_mostly = {
         .func           = ftrace_stub,
         .flags          = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_STUB,
+        INIT_OPS_HASH(ftrace_list_end)
 };
 
 /* ftrace_enabled is a method to turn ftrace on or off */
@@ -140,7 +146,8 @@ static inline void ftrace_ops_init(struct ftrace_ops *ops)
 {
 #ifdef CONFIG_DYNAMIC_FTRACE
         if (!(ops->flags & FTRACE_OPS_FL_INITIALIZED)) {
-                mutex_init(&ops->regex_lock);
+                mutex_init(&ops->local_hash.regex_lock);
+                ops->func_hash = &ops->local_hash;
                 ops->flags |= FTRACE_OPS_FL_INITIALIZED;
         }
 #endif
@@ -899,7 +906,7 @@ static void unregister_ftrace_profiler(void)
 static struct ftrace_ops ftrace_profile_ops __read_mostly = {
         .func           = function_profile_call,
         .flags          = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
-        INIT_REGEX_LOCK(ftrace_profile_ops)
+        INIT_OPS_HASH(ftrace_profile_ops)
 };
 
 static int register_ftrace_profiler(void)
@@ -1081,11 +1088,12 @@ static const struct ftrace_hash empty_hash = {
 #define EMPTY_HASH      ((struct ftrace_hash *)&empty_hash)
 
 static struct ftrace_ops global_ops = {
-        .func                   = ftrace_stub,
-        .notrace_hash           = EMPTY_HASH,
-        .filter_hash            = EMPTY_HASH,
-        .flags                  = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
-        INIT_REGEX_LOCK(global_ops)
+        .func                           = ftrace_stub,
+        .local_hash.notrace_hash        = EMPTY_HASH,
+        .local_hash.filter_hash         = EMPTY_HASH,
+        INIT_OPS_HASH(global_ops)
+        .flags                          = FTRACE_OPS_FL_RECURSION_SAFE |
+                                          FTRACE_OPS_FL_INITIALIZED,
 };
 
 struct ftrace_page {
@@ -1226,8 +1234,8 @@ static void free_ftrace_hash_rcu(struct ftrace_hash *hash)
 void ftrace_free_filter(struct ftrace_ops *ops)
 {
         ftrace_ops_init(ops);
-        free_ftrace_hash(ops->filter_hash);
-        free_ftrace_hash(ops->notrace_hash);
+        free_ftrace_hash(ops->func_hash->filter_hash);
+        free_ftrace_hash(ops->func_hash->notrace_hash);
 }
 
 static struct ftrace_hash *alloc_ftrace_hash(int size_bits)
@@ -1288,9 +1296,9 @@ alloc_and_copy_ftrace_hash(int size_bits, struct ftrace_hash *hash)
 }
 
 static void
-ftrace_hash_rec_disable(struct ftrace_ops *ops, int filter_hash);
+ftrace_hash_rec_disable_modify(struct ftrace_ops *ops, int filter_hash);
 static void
-ftrace_hash_rec_enable(struct ftrace_ops *ops, int filter_hash);
+ftrace_hash_rec_enable_modify(struct ftrace_ops *ops, int filter_hash);
 
 static int
 ftrace_hash_move(struct ftrace_ops *ops, int enable,
@@ -1342,13 +1350,13 @@ update:
          * Remove the current set, update the hash and add
          * them back.
          */
-        ftrace_hash_rec_disable(ops, enable);
+        ftrace_hash_rec_disable_modify(ops, enable);
 
         old_hash = *dst;
         rcu_assign_pointer(*dst, new_hash);
         free_ftrace_hash_rcu(old_hash);
 
-        ftrace_hash_rec_enable(ops, enable);
+        ftrace_hash_rec_enable_modify(ops, enable);
 
         return 0;
 }
@@ -1382,8 +1390,8 @@ ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip, void *regs)
                 return 0;
 #endif
 
-        filter_hash = rcu_dereference_raw_notrace(ops->filter_hash);
-        notrace_hash = rcu_dereference_raw_notrace(ops->notrace_hash);
+        filter_hash = rcu_dereference_raw_notrace(ops->func_hash->filter_hash);
+        notrace_hash = rcu_dereference_raw_notrace(ops->func_hash->notrace_hash);
 
         if ((ftrace_hash_empty(filter_hash) ||
              ftrace_lookup_ip(filter_hash, ip)) &&
@@ -1503,25 +1511,38 @@ static bool test_rec_ops_needs_regs(struct dyn_ftrace *rec)
 static void ftrace_remove_tramp(struct ftrace_ops *ops,
                                 struct dyn_ftrace *rec)
 {
-        struct ftrace_func_entry *entry;
-
-        entry = ftrace_lookup_ip(ops->tramp_hash, rec->ip);
-        if (!entry)
+        /* If TRAMP is not set, no ops should have a trampoline for this */
+        if (!(rec->flags & FTRACE_FL_TRAMP))
                 return;
 
+        rec->flags &= ~FTRACE_FL_TRAMP;
+
+        if ((!ftrace_hash_empty(ops->func_hash->filter_hash) &&
+             !ftrace_lookup_ip(ops->func_hash->filter_hash, rec->ip)) ||
+            ftrace_lookup_ip(ops->func_hash->notrace_hash, rec->ip))
+                return;
         /*
          * The tramp_hash entry will be removed at time
          * of update.
          */
         ops->nr_trampolines--;
-        rec->flags &= ~FTRACE_FL_TRAMP;
 }
 
-static void ftrace_clear_tramps(struct dyn_ftrace *rec)
+static void ftrace_clear_tramps(struct dyn_ftrace *rec, struct ftrace_ops *ops)
 {
         struct ftrace_ops *op;
 
+        /* If TRAMP is not set, no ops should have a trampoline for this */
+        if (!(rec->flags & FTRACE_FL_TRAMP))
+                return;
+
         do_for_each_ftrace_op(op, ftrace_ops_list) {
+                /*
+                 * This function is called to clear other tramps
+                 * not the one that is being updated.
+                 */
+                if (op == ops)
+                        continue;
                 if (op->nr_trampolines)
                         ftrace_remove_tramp(op, rec);
         } while_for_each_ftrace_op(op);
@@ -1554,14 +1575,14 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops,
          *   gets inversed.
          */
         if (filter_hash) {
-                hash = ops->filter_hash;
-                other_hash = ops->notrace_hash;
+                hash = ops->func_hash->filter_hash;
+                other_hash = ops->func_hash->notrace_hash;
                 if (ftrace_hash_empty(hash))
                         all = 1;
         } else {
                 inc = !inc;
-                hash = ops->notrace_hash;
-                other_hash = ops->filter_hash;
+                hash = ops->func_hash->notrace_hash;
+                other_hash = ops->func_hash->filter_hash;
                 /*
                  * If the notrace hash has no items,
                  * then there's nothing to do.
@@ -1622,13 +1643,10 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops,
                                 /*
                                  * If we are adding another function callback
                                  * to this function, and the previous had a
-                                 * trampoline used, then we need to go back to
-                                 * the default trampoline.
+                                 * custom trampoline in use, then we need to go
+                                 * back to the default trampoline.
                                  */
-                                rec->flags &= ~FTRACE_FL_TRAMP;
-
-                                /* remove trampolines from any ops for this rec */
-                                ftrace_clear_tramps(rec);
+                                ftrace_clear_tramps(rec, ops);
                         }
 
                         /*
@@ -1682,6 +1700,41 @@ static void ftrace_hash_rec_enable(struct ftrace_ops *ops,
         __ftrace_hash_rec_update(ops, filter_hash, 1);
 }
 
+static void ftrace_hash_rec_update_modify(struct ftrace_ops *ops,
+                                          int filter_hash, int inc)
+{
+        struct ftrace_ops *op;
+
+        __ftrace_hash_rec_update(ops, filter_hash, inc);
+
+        if (ops->func_hash != &global_ops.local_hash)
+                return;
+
+        /*
+         * If the ops shares the global_ops hash, then we need to update
+         * all ops that are enabled and use this hash.
+         */
+        do_for_each_ftrace_op(op, ftrace_ops_list) {
+                /* Already done */
+                if (op == ops)
+                        continue;
+                if (op->func_hash == &global_ops.local_hash)
+                        __ftrace_hash_rec_update(op, filter_hash, inc);
+        } while_for_each_ftrace_op(op);
+}
+
+static void ftrace_hash_rec_disable_modify(struct ftrace_ops *ops,
+                                           int filter_hash)
+{
+        ftrace_hash_rec_update_modify(ops, filter_hash, 0);
+}
+
+static void ftrace_hash_rec_enable_modify(struct ftrace_ops *ops,
+                                          int filter_hash)
+{
+        ftrace_hash_rec_update_modify(ops, filter_hash, 1);
+}
+
 static void print_ip_ins(const char *fmt, unsigned char *p)
 {
         int i;
@@ -1896,8 +1949,8 @@ unsigned long ftrace_get_addr_new(struct dyn_ftrace *rec)
         if (rec->flags & FTRACE_FL_TRAMP) {
                 ops = ftrace_find_tramp_ops_new(rec);
                 if (FTRACE_WARN_ON(!ops || !ops->trampoline)) {
-                        pr_warning("Bad trampoline accounting at: %p (%pS)\n",
-                                    (void *)rec->ip, (void *)rec->ip);
+                        pr_warn("Bad trampoline accounting at: %p (%pS) (%lx)\n",
+                                (void *)rec->ip, (void *)rec->ip, rec->flags);
                         /* Ftrace is shutting down, return anything */
                         return (unsigned long)FTRACE_ADDR;
                 }
@@ -1964,7 +2017,7 @@ __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
                 return ftrace_make_call(rec, ftrace_addr);
 
         case FTRACE_UPDATE_MAKE_NOP:
-                return ftrace_make_nop(NULL, rec, ftrace_addr);
+                return ftrace_make_nop(NULL, rec, ftrace_old_addr);
 
         case FTRACE_UPDATE_MODIFY_CALL:
                 return ftrace_modify_call(rec, ftrace_old_addr, ftrace_addr);
@@ -2227,7 +2280,10 @@ static int ftrace_save_ops_tramp_hash(struct ftrace_ops *ops)
         } while_for_each_ftrace_rec();
 
         /* The number of recs in the hash must match nr_trampolines */
-        FTRACE_WARN_ON(ops->tramp_hash->count != ops->nr_trampolines);
+        if (FTRACE_WARN_ON(ops->tramp_hash->count != ops->nr_trampolines))
+                pr_warn("count=%ld trampolines=%d\n",
+                        ops->tramp_hash->count,
+                        ops->nr_trampolines);
 
         return 0;
 }
@@ -2436,8 +2492,8 @@ static inline int ops_traces_mod(struct ftrace_ops *ops)
          * Filter_hash being empty will default to trace module.
          * But notrace hash requires a test of individual module functions.
          */
-        return ftrace_hash_empty(ops->filter_hash) &&
-                ftrace_hash_empty(ops->notrace_hash);
+        return ftrace_hash_empty(ops->func_hash->filter_hash) &&
+                ftrace_hash_empty(ops->func_hash->notrace_hash);
 }
 
 /*
@@ -2459,12 +2515,12 @@ ops_references_rec(struct ftrace_ops *ops, struct dyn_ftrace *rec)
                 return 0;
 
         /* The function must be in the filter */
-        if (!ftrace_hash_empty(ops->filter_hash) &&
-            !ftrace_lookup_ip(ops->filter_hash, rec->ip))
+        if (!ftrace_hash_empty(ops->func_hash->filter_hash) &&
+            !ftrace_lookup_ip(ops->func_hash->filter_hash, rec->ip))
                 return 0;
 
         /* If in notrace hash, we ignore it too */
-        if (ftrace_lookup_ip(ops->notrace_hash, rec->ip))
+        if (ftrace_lookup_ip(ops->func_hash->notrace_hash, rec->ip))
                 return 0;
 
         return 1;
@@ -2785,10 +2841,10 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
         } else {
                 rec = &iter->pg->records[iter->idx++];
                 if (((iter->flags & FTRACE_ITER_FILTER) &&
-                     !(ftrace_lookup_ip(ops->filter_hash, rec->ip))) ||
+                     !(ftrace_lookup_ip(ops->func_hash->filter_hash, rec->ip))) ||
 
                     ((iter->flags & FTRACE_ITER_NOTRACE) &&
-                     !ftrace_lookup_ip(ops->notrace_hash, rec->ip)) ||
+                     !ftrace_lookup_ip(ops->func_hash->notrace_hash, rec->ip)) ||
 
                     ((iter->flags & FTRACE_ITER_ENABLED) &&
                      !(rec->flags & FTRACE_FL_ENABLED))) {
@@ -2837,9 +2893,9 @@ static void *t_start(struct seq_file *m, loff_t *pos)
          * functions are enabled.
          */
         if ((iter->flags & FTRACE_ITER_FILTER &&
-             ftrace_hash_empty(ops->filter_hash)) ||
+             ftrace_hash_empty(ops->func_hash->filter_hash)) ||
             (iter->flags & FTRACE_ITER_NOTRACE &&
-             ftrace_hash_empty(ops->notrace_hash))) {
+             ftrace_hash_empty(ops->func_hash->notrace_hash))) {
                 if (*pos > 0)
                         return t_hash_start(m, pos);
                 iter->flags |= FTRACE_ITER_PRINTALL;
@@ -3001,12 +3057,12 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
         iter->ops = ops;
         iter->flags = flag;
 
-        mutex_lock(&ops->regex_lock);
+        mutex_lock(&ops->func_hash->regex_lock);
 
         if (flag & FTRACE_ITER_NOTRACE)
-                hash = ops->notrace_hash;
+                hash = ops->func_hash->notrace_hash;
         else
-                hash = ops->filter_hash;
+                hash = ops->func_hash->filter_hash;
 
         if (file->f_mode & FMODE_WRITE) {
                 const int size_bits = FTRACE_HASH_DEFAULT_BITS;
@@ -3041,7 +3097,7 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
                 file->private_data = iter;
 
  out_unlock:
-        mutex_unlock(&ops->regex_lock);
+        mutex_unlock(&ops->func_hash->regex_lock);
 
         return ret;
 }
@@ -3279,7 +3335,7 @@ static struct ftrace_ops trace_probe_ops __read_mostly =
 {
         .func           = function_trace_probe_call,
         .flags          = FTRACE_OPS_FL_INITIALIZED,
-        INIT_REGEX_LOCK(trace_probe_ops)
+        INIT_OPS_HASH(trace_probe_ops)
 };
 
 static int ftrace_probe_registered;
@@ -3342,7 +3398,7 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                               void *data)
 {
         struct ftrace_func_probe *entry;
-        struct ftrace_hash **orig_hash = &trace_probe_ops.filter_hash;
+        struct ftrace_hash **orig_hash = &trace_probe_ops.func_hash->filter_hash;
         struct ftrace_hash *hash;
         struct ftrace_page *pg;
         struct dyn_ftrace *rec;
@@ -3359,7 +3415,7 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
         if (WARN_ON(not))
                 return -EINVAL;
 
-        mutex_lock(&trace_probe_ops.regex_lock);
+        mutex_lock(&trace_probe_ops.func_hash->regex_lock);
 
         hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
         if (!hash) {
@@ -3428,7 +3484,7 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
  out_unlock:
         mutex_unlock(&ftrace_lock);
  out:
-        mutex_unlock(&trace_probe_ops.regex_lock);
+        mutex_unlock(&trace_probe_ops.func_hash->regex_lock);
         free_ftrace_hash(hash);
 
         return count;
@@ -3446,7 +3502,7 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
         struct ftrace_func_entry *rec_entry;
         struct ftrace_func_probe *entry;
         struct ftrace_func_probe *p;
-        struct ftrace_hash **orig_hash = &trace_probe_ops.filter_hash;
+        struct ftrace_hash **orig_hash = &trace_probe_ops.func_hash->filter_hash;
         struct list_head free_list;
         struct ftrace_hash *hash;
         struct hlist_node *tmp;
@@ -3468,7 +3524,7 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                         return;
         }
 
-        mutex_lock(&trace_probe_ops.regex_lock);
+        mutex_lock(&trace_probe_ops.func_hash->regex_lock);
 
         hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
         if (!hash)
@@ -3521,7 +3577,7 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
         mutex_unlock(&ftrace_lock);
                 
  out_unlock:
-        mutex_unlock(&trace_probe_ops.regex_lock);
+        mutex_unlock(&trace_probe_ops.func_hash->regex_lock);
         free_ftrace_hash(hash);
 }
 
@@ -3717,12 +3773,12 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
         if (unlikely(ftrace_disabled))
                 return -ENODEV;
 
-        mutex_lock(&ops->regex_lock);
+        mutex_lock(&ops->func_hash->regex_lock);
 
         if (enable)
-                orig_hash = &ops->filter_hash;
+                orig_hash = &ops->func_hash->filter_hash;
         else
-                orig_hash = &ops->notrace_hash;
+                orig_hash = &ops->func_hash->notrace_hash;
 
         if (reset)
                 hash = alloc_ftrace_hash(FTRACE_HASH_DEFAULT_BITS);
@@ -3752,7 +3808,7 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
         mutex_unlock(&ftrace_lock);
 
  out_regex_unlock:
-        mutex_unlock(&ops->regex_lock);
+        mutex_unlock(&ops->func_hash->regex_lock);
 
         free_ftrace_hash(hash);
         return ret;
@@ -3975,15 +4031,15 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
 
         trace_parser_put(parser);
 
-        mutex_lock(&iter->ops->regex_lock);
+        mutex_lock(&iter->ops->func_hash->regex_lock);
 
         if (file->f_mode & FMODE_WRITE) {
                 filter_hash = !!(iter->flags & FTRACE_ITER_FILTER);
 
                 if (filter_hash)
-                        orig_hash = &iter->ops->filter_hash;
+                        orig_hash = &iter->ops->func_hash->filter_hash;
                 else
-                        orig_hash = &iter->ops->notrace_hash;
+                        orig_hash = &iter->ops->func_hash->notrace_hash;
 
                 mutex_lock(&ftrace_lock);
                 ret = ftrace_hash_move(iter->ops, filter_hash,
@@ -3994,7 +4050,7 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
                 mutex_unlock(&ftrace_lock);
         }
 
-        mutex_unlock(&iter->ops->regex_lock);
+        mutex_unlock(&iter->ops->func_hash->regex_lock);
         free_ftrace_hash(iter->hash);
         kfree(iter);
 
@@ -4611,7 +4667,6 @@ void __init ftrace_init(void)
 static struct ftrace_ops global_ops = {
         .func                   = ftrace_stub,
         .flags                  = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
-        INIT_REGEX_LOCK(global_ops)
 };
 
 static int __init ftrace_nodyn_init(void)
@@ -4713,7 +4768,7 @@ ftrace_ops_control_func(unsigned long ip, unsigned long parent_ip,
 static struct ftrace_ops control_ops = {
         .func   = ftrace_ops_control_func,
         .flags  = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
-        INIT_REGEX_LOCK(control_ops)
+        INIT_OPS_HASH(control_ops)
 };
 
 static inline void
@@ -5145,6 +5200,17 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
+static struct ftrace_ops graph_ops = {
+        .func                   = ftrace_stub,
+        .flags                  = FTRACE_OPS_FL_RECURSION_SAFE |
+                                   FTRACE_OPS_FL_INITIALIZED |
+                                   FTRACE_OPS_FL_STUB,
+#ifdef FTRACE_GRAPH_TRAMP_ADDR
+        .trampoline             = FTRACE_GRAPH_TRAMP_ADDR,
+#endif
+        ASSIGN_OPS_HASH(graph_ops, &global_ops.local_hash)
+};
+
 static int ftrace_graph_active;
 
 int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace)
@@ -5307,12 +5373,28 @@ static int ftrace_graph_entry_test(struct ftrace_graph_ent *trace)
  */
 static void update_function_graph_func(void)
 {
-        if (ftrace_ops_list == &ftrace_list_end ||
-            (ftrace_ops_list == &global_ops &&
-             global_ops.next == &ftrace_list_end))
-                ftrace_graph_entry = __ftrace_graph_entry;
-        else
+        struct ftrace_ops *op;
+        bool do_test = false;
+
+        /*
+         * The graph and global ops share the same set of functions
+         * to test. If any other ops is on the list, then
+         * the graph tracing needs to test if its the function
+         * it should call.
+         */
+        do_for_each_ftrace_op(op, ftrace_ops_list) {
+                if (op != &global_ops && op != &graph_ops &&
+                    op != &ftrace_list_end) {
+                        do_test = true;
+                        /* in double loop, break out with goto */
+                        goto out;
+                }
+        } while_for_each_ftrace_op(op);
+ out:
+        if (do_test)
                 ftrace_graph_entry = ftrace_graph_entry_test;
+        else
+                ftrace_graph_entry = __ftrace_graph_entry;
 }
 
 static struct notifier_block ftrace_suspend_notifier = {
@@ -5353,16 +5435,7 @@ int register_ftrace_graph(trace_func_graph_ret_t retfunc,
         ftrace_graph_entry = ftrace_graph_entry_test;
         update_function_graph_func();
 
-        /* Function graph doesn't use the .func field of global_ops */
-        global_ops.flags |= FTRACE_OPS_FL_STUB;
-
-#ifdef CONFIG_DYNAMIC_FTRACE
-        /* Optimize function graph calling (if implemented by arch) */
-        if (FTRACE_GRAPH_TRAMP_ADDR != 0)
-                global_ops.trampoline = FTRACE_GRAPH_TRAMP_ADDR;
-#endif
-
-        ret = ftrace_startup(&global_ops, FTRACE_START_FUNC_RET);
+        ret = ftrace_startup(&graph_ops, FTRACE_START_FUNC_RET);
 
 out:
         mutex_unlock(&ftrace_lock);
@@ -5380,12 +5453,7 @@ void unregister_ftrace_graph(void)
         ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
         ftrace_graph_entry = ftrace_graph_entry_stub;
         __ftrace_graph_entry = ftrace_graph_entry_stub;
-        ftrace_shutdown(&global_ops, FTRACE_STOP_FUNC_RET);
-        global_ops.flags &= ~FTRACE_OPS_FL_STUB;
-#ifdef CONFIG_DYNAMIC_FTRACE
-        if (FTRACE_GRAPH_TRAMP_ADDR != 0)
-                global_ops.trampoline = 0;
-#endif
+        ftrace_shutdown(&graph_ops, FTRACE_STOP_FUNC_RET);
         unregister_pm_notifier(&ftrace_suspend_notifier);
         unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
 
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index afb04b9b818a..b38fb2b9e237 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -626,8 +626,22 @@ int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
                 work = &cpu_buffer->irq_work;
         }
 
-        work->waiters_pending = true;
         poll_wait(filp, &work->waiters, poll_table);
+        work->waiters_pending = true;
+        /*
+         * There's a tight race between setting the waiters_pending and
+         * checking if the ring buffer is empty.  Once the waiters_pending bit
+         * is set, the next event will wake the task up, but we can get stuck
+         * if there's only a single event in.
+         *
+         * FIXME: Ideally, we need a memory barrier on the writer side as well,
+         * but adding a memory barrier to all events will cause too much of a
+         * performance hit in the fast path.  We only need a memory barrier when
+         * the buffer goes from empty to having content.  But as this race is
+         * extremely small, and it's not a problem if another event comes in, we
+         * will fix it later.
+         */
+        smp_mb();
 
         if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
             (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))