Merge branch 'linus' into sched/core

Merge reason: we want to queue up dependent cleanup

Signed-off-by: Ingo Molnar <mingo@elte.hu>

14 files changed, 188 insertions, 60 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 21aa7b3001fb..676149a4ac5f 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -914,6 +914,15 @@ NORET_TYPE void do_exit(long code)
         if (unlikely(!tsk->pid))
                 panic("Attempted to kill the idle task!");
 
+        /*
+         * If do_exit is called because this processes oopsed, it's possible
+         * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
+         * continuing. Amongst other possible reasons, this is to prevent
+         * mm_release()->clear_child_tid() from writing to a user-controlled
+         * kernel address.
+         */
+        set_fs(USER_DS);
+
         tracehook_report_exit(&code);
 
         validate_creds_for_do_exit(tsk);
diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index 2c9120f0afca..e5325825aeb6 100644
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -620,7 +620,7 @@ static struct pmu perf_breakpoint = {
         .read           = hw_breakpoint_pmu_read,
 };
 
-static int __init init_hw_breakpoint(void)
+int __init init_hw_breakpoint(void)
 {
         unsigned int **task_bp_pinned;
         int cpu, err_cpu;
@@ -655,6 +655,5 @@ static int __init init_hw_breakpoint(void)
 
         return -ENOMEM;
 }
-core_initcall(init_hw_breakpoint);
 
 
diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index 01b1d3a88983..6c8a2a9f8a7b 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -214,7 +214,7 @@ static int irq_spurious_proc_show(struct seq_file *m, void *v)
 
 static int irq_spurious_proc_open(struct inode *inode, struct file *file)
 {
-        return single_open(file, irq_spurious_proc_show, NULL);
+        return single_open(file, irq_spurious_proc_show, PDE(inode)->data);
 }
 
 static const struct file_operations irq_spurious_proc_fops = {
diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index f16763ff8481..90f881904bb1 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -145,7 +145,9 @@ void irq_work_run(void)
                  * Clear the BUSY bit and return to the free state if
                  * no-one else claimed it meanwhile.
                  */
-                cmpxchg(&entry->next, next_flags(NULL, IRQ_WORK_BUSY), NULL);
+                (void)cmpxchg(&entry->next,
+                              next_flags(NULL, IRQ_WORK_BUSY),
+                              NULL);
         }
 }
 EXPORT_SYMBOL_GPL(irq_work_run);
diff --git a/kernel/module.c b/kernel/module.c
index 437a74a7524a..d190664f25ff 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2326,6 +2326,18 @@ static void find_module_sections(struct module *mod, struct load_info *info)
         kmemleak_scan_area(mod->trace_events, sizeof(*mod->trace_events) *
                            mod->num_trace_events, GFP_KERNEL);
 #endif
+#ifdef CONFIG_TRACING
+        mod->trace_bprintk_fmt_start = section_objs(info, "__trace_printk_fmt",
+                                         sizeof(*mod->trace_bprintk_fmt_start),
+                                         &mod->num_trace_bprintk_fmt);
+        /*
+         * This section contains pointers to allocated objects in the trace
+         * code and not scanning it leads to false positives.
+         */
+        kmemleak_scan_area(mod->trace_bprintk_fmt_start,
+                           sizeof(*mod->trace_bprintk_fmt_start) *
+                           mod->num_trace_bprintk_fmt, GFP_KERNEL);
+#endif
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
         /* sechdrs[0].sh_size is always zero */
         mod->ftrace_callsites = section_objs(info, "__mcount_loc",
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index cb6c0d2af68f..eac7e3364335 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -31,6 +31,7 @@
 #include <linux/kernel_stat.h>
 #include <linux/perf_event.h>
 #include <linux/ftrace_event.h>
+#include <linux/hw_breakpoint.h>
 
 #include <asm/irq_regs.h>
 
@@ -1286,8 +1287,6 @@ void __perf_event_task_sched_out(struct task_struct *task,
 {
         int ctxn;
 
-        perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, 1, NULL, 0);
-
         for_each_task_context_nr(ctxn)
                 perf_event_context_sched_out(task, ctxn, next);
 }
@@ -1621,8 +1620,12 @@ static void rotate_ctx(struct perf_event_context *ctx)
 {
         raw_spin_lock(&ctx->lock);
 
-        /* Rotate the first entry last of non-pinned groups */
-        list_rotate_left(&ctx->flexible_groups);
+        /*
+         * Rotate the first entry last of non-pinned groups. Rotation might be
+         * disabled by the inheritance code.
+         */
+        if (!ctx->rotate_disable)
+                list_rotate_left(&ctx->flexible_groups);
 
         raw_spin_unlock(&ctx->lock);
 }
@@ -2234,11 +2237,6 @@ int perf_event_release_kernel(struct perf_event *event)
         raw_spin_unlock_irq(&ctx->lock);
         mutex_unlock(&ctx->mutex);
 
-        mutex_lock(&event->owner->perf_event_mutex);
-        list_del_init(&event->owner_entry);
-        mutex_unlock(&event->owner->perf_event_mutex);
-        put_task_struct(event->owner);
-
         free_event(event);
 
         return 0;
@@ -2251,9 +2249,43 @@ EXPORT_SYMBOL_GPL(perf_event_release_kernel);
 static int perf_release(struct inode *inode, struct file *file)
 {
         struct perf_event *event = file->private_data;
+        struct task_struct *owner;
 
         file->private_data = NULL;
 
+        rcu_read_lock();
+        owner = ACCESS_ONCE(event->owner);
+        /*
+         * Matches the smp_wmb() in perf_event_exit_task(). If we observe
+         * !owner it means the list deletion is complete and we can indeed
+         * free this event, otherwise we need to serialize on
+         * owner->perf_event_mutex.
+         */
+        smp_read_barrier_depends();
+        if (owner) {
+                /*
+                 * Since delayed_put_task_struct() also drops the last
+                 * task reference we can safely take a new reference
+                 * while holding the rcu_read_lock().
+                 */
+                get_task_struct(owner);
+        }
+        rcu_read_unlock();
+
+        if (owner) {
+                mutex_lock(&owner->perf_event_mutex);
+                /*
+                 * We have to re-check the event->owner field, if it is cleared
+                 * we raced with perf_event_exit_task(), acquiring the mutex
+                 * ensured they're done, and we can proceed with freeing the
+                 * event.
+                 */
+                if (event->owner)
+                        list_del_init(&event->owner_entry);
+                mutex_unlock(&owner->perf_event_mutex);
+                put_task_struct(owner);
+        }
+
         return perf_event_release_kernel(event);
 }
 
@@ -5677,7 +5709,7 @@ SYSCALL_DEFINE5(perf_event_open,
         mutex_unlock(&ctx->mutex);
 
         event->owner = current;
-        get_task_struct(current);
+
         mutex_lock(&current->perf_event_mutex);
         list_add_tail(&event->owner_entry, &current->perf_event_list);
         mutex_unlock(&current->perf_event_mutex);
@@ -5745,12 +5777,6 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
         ++ctx->generation;
         mutex_unlock(&ctx->mutex);
 
-        event->owner = current;
-        get_task_struct(current);
-        mutex_lock(&current->perf_event_mutex);
-        list_add_tail(&event->owner_entry, &current->perf_event_list);
-        mutex_unlock(&current->perf_event_mutex);
-
         return event;
 
 err_free:
@@ -5901,8 +5927,24 @@ again:
  */
 void perf_event_exit_task(struct task_struct *child)
 {
+        struct perf_event *event, *tmp;
         int ctxn;
 
+        mutex_lock(&child->perf_event_mutex);
+        list_for_each_entry_safe(event, tmp, &child->perf_event_list,
+                                 owner_entry) {
+                list_del_init(&event->owner_entry);
+
+                /*
+                 * Ensure the list deletion is visible before we clear
+                 * the owner, closes a race against perf_release() where
+                 * we need to serialize on the owner->perf_event_mutex.
+                 */
+                smp_wmb();
+                event->owner = NULL;
+        }
+        mutex_unlock(&child->perf_event_mutex);
+
         for_each_task_context_nr(ctxn)
                 perf_event_exit_task_context(child, ctxn);
 }
@@ -6122,6 +6164,7 @@ int perf_event_init_context(struct task_struct *child, int ctxn)
         struct perf_event *event;
         struct task_struct *parent = current;
         int inherited_all = 1;
+        unsigned long flags;
         int ret = 0;
 
         child->perf_event_ctxp[ctxn] = NULL;
@@ -6162,6 +6205,15 @@ int perf_event_init_context(struct task_struct *child, int ctxn)
                         break;
         }
 
+        /*
+         * We can't hold ctx->lock when iterating the ->flexible_group list due
+         * to allocations, but we need to prevent rotation because
+         * rotate_ctx() will change the list from interrupt context.
+         */
+        raw_spin_lock_irqsave(&parent_ctx->lock, flags);
+        parent_ctx->rotate_disable = 1;
+        raw_spin_unlock_irqrestore(&parent_ctx->lock, flags);
+
         list_for_each_entry(event, &parent_ctx->flexible_groups, group_entry) {
                 ret = inherit_task_group(event, parent, parent_ctx,
                                          child, ctxn, &inherited_all);
@@ -6169,6 +6221,10 @@ int perf_event_init_context(struct task_struct *child, int ctxn)
                         break;
         }
 
+        raw_spin_lock_irqsave(&parent_ctx->lock, flags);
+        parent_ctx->rotate_disable = 0;
+        raw_spin_unlock_irqrestore(&parent_ctx->lock, flags);
+
         child_ctx = child->perf_event_ctxp[ctxn];
 
         if (child_ctx && inherited_all) {
@@ -6321,6 +6377,8 @@ perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
 
 void __init perf_event_init(void)
 {
+        int ret;
+
         perf_event_init_all_cpus();
         init_srcu_struct(&pmus_srcu);
         perf_pmu_register(&perf_swevent);
@@ -6328,4 +6386,7 @@ void __init perf_event_init(void)
         perf_pmu_register(&perf_task_clock);
         perf_tp_register();
         perf_cpu_notifier(perf_cpu_notify);
+
+        ret = init_hw_breakpoint();
+        WARN(ret, "hw_breakpoint initialization failed with: %d", ret);
 }
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 6842eeba5879..05bb7173850e 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -37,13 +37,13 @@ static int check_clock(const clockid_t which_clock)
         if (pid == 0)
                 return 0;
 
-        read_lock(&tasklist_lock);
+        rcu_read_lock();
         p = find_task_by_vpid(pid);
         if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
-                   same_thread_group(p, current) : thread_group_leader(p))) {
+                   same_thread_group(p, current) : has_group_leader_pid(p))) {
                 error = -EINVAL;
         }
-        read_unlock(&tasklist_lock);
+        rcu_read_unlock();
 
         return error;
 }
@@ -390,7 +390,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
 
         INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 
-        read_lock(&tasklist_lock);
+        rcu_read_lock();
         if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
                 if (pid == 0) {
                         p = current;
@@ -404,7 +404,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
                         p = current->group_leader;
                 } else {
                         p = find_task_by_vpid(pid);
-                        if (p && !thread_group_leader(p))
+                        if (p && !has_group_leader_pid(p))
                                 p = NULL;
                 }
         }
@@ -414,7 +414,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
         } else {
                 ret = -EINVAL;
         }
-        read_unlock(&tasklist_lock);
+        rcu_read_unlock();
 
         return ret;
 }
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 657272e91d0a..048d0b514831 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -327,7 +327,6 @@ static int create_image(int platform_mode)
 int hibernation_snapshot(int platform_mode)
 {
         int error;
-        gfp_t saved_mask;
 
         error = platform_begin(platform_mode);
         if (error)
@@ -339,7 +338,7 @@ int hibernation_snapshot(int platform_mode)
                 goto Close;
 
         suspend_console();
-        saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
+        pm_restrict_gfp_mask();
         error = dpm_suspend_start(PMSG_FREEZE);
         if (error)
                 goto Recover_platform;
@@ -348,7 +347,10 @@ int hibernation_snapshot(int platform_mode)
                 goto Recover_platform;
 
         error = create_image(platform_mode);
-        /* Control returns here after successful restore */
+        /*
+         * Control returns here (1) after the image has been created or the
+         * image creation has failed and (2) after a successful restore.
+         */
 
  Resume_devices:
         /* We may need to release the preallocated image pages here. */
@@ -357,7 +359,10 @@ int hibernation_snapshot(int platform_mode)
 
         dpm_resume_end(in_suspend ?
                 (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE);
-        set_gfp_allowed_mask(saved_mask);
+
+        if (error || !in_suspend)
+                pm_restore_gfp_mask();
+
         resume_console();
  Close:
         platform_end(platform_mode);
@@ -452,17 +457,16 @@ static int resume_target_kernel(bool platform_mode)
 int hibernation_restore(int platform_mode)
 {
         int error;
-        gfp_t saved_mask;
 
         pm_prepare_console();
         suspend_console();
-        saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
+        pm_restrict_gfp_mask();
         error = dpm_suspend_start(PMSG_QUIESCE);
         if (!error) {
                 error = resume_target_kernel(platform_mode);
                 dpm_resume_end(PMSG_RECOVER);
         }
-        set_gfp_allowed_mask(saved_mask);
+        pm_restore_gfp_mask();
         resume_console();
         pm_restore_console();
         return error;
@@ -476,7 +480,6 @@ int hibernation_restore(int platform_mode)
 int hibernation_platform_enter(void)
 {
         int error;
-        gfp_t saved_mask;
 
         if (!hibernation_ops)
                 return -ENOSYS;
@@ -492,7 +495,6 @@ int hibernation_platform_enter(void)
 
         entering_platform_hibernation = true;
         suspend_console();
-        saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
         error = dpm_suspend_start(PMSG_HIBERNATE);
         if (error) {
                 if (hibernation_ops->recover)
@@ -536,7 +538,6 @@ int hibernation_platform_enter(void)
  Resume_devices:
         entering_platform_hibernation = false;
         dpm_resume_end(PMSG_RESTORE);
-        set_gfp_allowed_mask(saved_mask);
         resume_console();
 
  Close:
@@ -646,6 +647,7 @@ int hibernate(void)
                 swsusp_free();
                 if (!error)
                         power_down();
+                pm_restore_gfp_mask();
         } else {
                 pr_debug("PM: Image restored successfully.\n");
         }
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 7335952ee473..ecf770509d0d 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -197,7 +197,6 @@ static int suspend_enter(suspend_state_t state)
 int suspend_devices_and_enter(suspend_state_t state)
 {
         int error;
-        gfp_t saved_mask;
 
         if (!suspend_ops)
                 return -ENOSYS;
@@ -208,7 +207,7 @@ int suspend_devices_and_enter(suspend_state_t state)
                         goto Close;
         }
         suspend_console();
-        saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
+        pm_restrict_gfp_mask();
         suspend_test_start();
         error = dpm_suspend_start(PMSG_SUSPEND);
         if (error) {
@@ -225,7 +224,7 @@ int suspend_devices_and_enter(suspend_state_t state)
         suspend_test_start();
         dpm_resume_end(PMSG_RESUME);
         suspend_test_finish("resume devices");
-        set_gfp_allowed_mask(saved_mask);
+        pm_restore_gfp_mask();
         resume_console();
  Close:
         if (suspend_ops->end)
diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index a0e4a86ccf94..baf667bb2794 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -6,6 +6,7 @@
  *
  * Copyright (C) 1998,2001-2005 Pavel Machek <pavel@ucw.cz>
  * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
+ * Copyright (C) 2010 Bojan Smojver <bojan@rexursive.com>
  *
  * This file is released under the GPLv2.
  *
@@ -753,30 +754,43 @@ static int load_image_lzo(struct swap_map_handle *handle,
 {
         unsigned int m;
         int error = 0;
+        struct bio *bio;
         struct timeval start;
         struct timeval stop;
         unsigned nr_pages;
-        size_t off, unc_len, cmp_len;
-        unsigned char *unc, *cmp, *page;
+        size_t i, off, unc_len, cmp_len;
+        unsigned char *unc, *cmp, *page[LZO_CMP_PAGES];
 
-        page = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
-        if (!page) {
-                printk(KERN_ERR "PM: Failed to allocate LZO page\n");
-                return -ENOMEM;
+        for (i = 0; i < LZO_CMP_PAGES; i++) {
+                page[i] = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
+                if (!page[i]) {
+                        printk(KERN_ERR "PM: Failed to allocate LZO page\n");
+
+                        while (i)
+                                free_page((unsigned long)page[--i]);
+
+                        return -ENOMEM;
+                }
         }
 
         unc = vmalloc(LZO_UNC_SIZE);
         if (!unc) {
                 printk(KERN_ERR "PM: Failed to allocate LZO uncompressed\n");
-                free_page((unsigned long)page);
+
+                for (i = 0; i < LZO_CMP_PAGES; i++)
+                        free_page((unsigned long)page[i]);
+
                 return -ENOMEM;
         }
 
         cmp = vmalloc(LZO_CMP_SIZE);
         if (!cmp) {
                 printk(KERN_ERR "PM: Failed to allocate LZO compressed\n");
+
                 vfree(unc);
-                free_page((unsigned long)page);
+                for (i = 0; i < LZO_CMP_PAGES; i++)
+                        free_page((unsigned long)page[i]);
+
                 return -ENOMEM;
         }
 
@@ -787,6 +801,7 @@ static int load_image_lzo(struct swap_map_handle *handle,
         if (!m)
                 m = 1;
         nr_pages = 0;
+        bio = NULL;
         do_gettimeofday(&start);
 
         error = snapshot_write_next(snapshot);
@@ -794,11 +809,11 @@ static int load_image_lzo(struct swap_map_handle *handle,
                 goto out_finish;
 
         for (;;) {
-                error = swap_read_page(handle, page, NULL); /* sync */
+                error = swap_read_page(handle, page[0], NULL); /* sync */
                 if (error)
                         break;
 
-                cmp_len = *(size_t *)page;
+                cmp_len = *(size_t *)page[0];
                 if (unlikely(!cmp_len ||
                              cmp_len > lzo1x_worst_compress(LZO_UNC_SIZE))) {
                         printk(KERN_ERR "PM: Invalid LZO compressed length\n");
@@ -806,13 +821,20 @@ static int load_image_lzo(struct swap_map_handle *handle,
                         break;
                 }
 
-                memcpy(cmp, page, PAGE_SIZE);
-                for (off = PAGE_SIZE; off < LZO_HEADER + cmp_len; off += PAGE_SIZE) {
-                        error = swap_read_page(handle, page, NULL); /* sync */
+                for (off = PAGE_SIZE, i = 1;
+                     off < LZO_HEADER + cmp_len; off += PAGE_SIZE, i++) {
+                        error = swap_read_page(handle, page[i], &bio);
                         if (error)
                                 goto out_finish;
+                }
 
-                        memcpy(cmp + off, page, PAGE_SIZE);
+                error = hib_wait_on_bio_chain(&bio); /* need all data now */
+                if (error)
+                        goto out_finish;
+
+                for (off = 0, i = 0;
+                     off < LZO_HEADER + cmp_len; off += PAGE_SIZE, i++) {
+                        memcpy(cmp + off, page[i], PAGE_SIZE);
                 }
 
                 unc_len = LZO_UNC_SIZE;
@@ -857,7 +879,8 @@ out_finish:
 
         vfree(cmp);
         vfree(unc);
-        free_page((unsigned long)page);
+        for (i = 0; i < LZO_CMP_PAGES; i++)
+                free_page((unsigned long)page[i]);
 
         return error;
 }
diff --git a/kernel/power/user.c b/kernel/power/user.c
index e819e17877ca..1b2ea31e6bd8 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -263,6 +263,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
         case SNAPSHOT_UNFREEZE:
                 if (!data->frozen || data->ready)
                         break;
+                pm_restore_gfp_mask();
                 thaw_processes();
                 usermodehelper_enable();
                 data->frozen = 0;
@@ -275,6 +276,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
                         error = -EPERM;
                         break;
                 }
+                pm_restore_gfp_mask();
                 error = hibernation_snapshot(data->platform_support);
                 if (!error)
                         error = put_user(in_suspend, (int __user *)arg);
diff --git a/kernel/printk.c b/kernel/printk.c
index 9a2264fc42ca..a23315dc4498 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1082,13 +1082,15 @@ void printk_tick(void)
 
 int printk_needs_cpu(int cpu)
 {
+        if (unlikely(cpu_is_offline(cpu)))
+                printk_tick();
         return per_cpu(printk_pending, cpu);
 }
 
 void wake_up_klogd(void)
 {
         if (waitqueue_active(&log_wait))
-                __raw_get_cpu_var(printk_pending) = 1;
+                this_cpu_write(printk_pending, 1);
 }
 
 /**
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index fdbdb5084c49..c88671718bc9 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1903,10 +1903,6 @@ static void pull_task(struct rq *src_rq, struct task_struct *p,
         set_task_cpu(p, this_cpu);
         activate_task(this_rq, p, 0);
         check_preempt_curr(this_rq, p, 0);
-
-        /* re-arm NEWIDLE balancing when moving tasks */
-        src_rq->avg_idle = this_rq->avg_idle = 2*sysctl_sched_migration_cost;
-        this_rq->idle_stamp = 0;
 }
 
 /*
@@ -3408,8 +3404,10 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
                 interval = msecs_to_jiffies(sd->balance_interval);
                 if (time_after(next_balance, sd->last_balance + interval))
                         next_balance = sd->last_balance + interval;
-                if (pulled_task)
+                if (pulled_task) {
+                        this_rq->idle_stamp = 0;
                         break;
+                }
         }
 
         raw_spin_lock(&this_rq->lock);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 042084157980..c380612273bf 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1283,6 +1283,8 @@ void trace_dump_stack(void)
         __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count());
 }
 
+static DEFINE_PER_CPU(int, user_stack_count);
+
 void
 ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
 {
@@ -1301,6 +1303,18 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
         if (unlikely(in_nmi()))
                 return;
 
+        /*
+         * prevent recursion, since the user stack tracing may
+         * trigger other kernel events.
+         */
+        preempt_disable();
+        if (__this_cpu_read(user_stack_count))
+                goto out;
+
+        __this_cpu_inc(user_stack_count);
+
+
+
         event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK,
                                           sizeof(*entry), flags, pc);
         if (!event)
@@ -1318,6 +1332,11 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
         save_stack_trace_user(&trace);
         if (!filter_check_discard(call, entry, buffer, event))
                 ring_buffer_unlock_commit(buffer, event);
+
+        __this_cpu_dec(user_stack_count);
+
+ out:
+        preempt_enable();
 }
 
 #ifdef UNUSED