9 files changed, 49 insertions, 24 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index ce1e48c2d93d..cce59cb5ee6a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -87,7 +87,7 @@ static void __exit_signal(struct task_struct *tsk)
 
         sighand = rcu_dereference_check(tsk->sighand,
                                         rcu_read_lock_held() ||
-                                        lockdep_is_held(&tasklist_lock));
+                                        lockdep_tasklist_lock_is_held());
         spin_lock(&sighand->siglock);
 
         posix_cpu_timers_exit(tsk);
diff --git a/kernel/fork.c b/kernel/fork.c
index 1beb6c303c41..4799c5f0e6d0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -86,7 +86,14 @@ int max_threads;		/* tunable limit on nr_threads */
 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
 
 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
-EXPORT_SYMBOL_GPL(tasklist_lock);
+
+#ifdef CONFIG_PROVE_RCU
+int lockdep_tasklist_lock_is_held(void)
+{
+        return lockdep_is_held(&tasklist_lock);
+}
+EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
+#endif /* #ifdef CONFIG_PROVE_RCU */
 
 int nr_processes(void)
 {
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 0c30d0455de1..681bc2e1e187 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3822,6 +3822,7 @@ void lockdep_rcu_dereference(const char *file, const int line)
         printk("%s:%d invoked rcu_dereference_check() without protection!\n",
                         file, line);
         printk("\nother info that might help us debug this:\n\n");
+        printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
         lockdep_print_held_locks(curr);
         printk("\nstack backtrace:\n");
         dump_stack();
diff --git a/kernel/pid.c b/kernel/pid.c
index 86b296943e5f..aebb30d9c233 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -367,7 +367,9 @@ struct task_struct *pid_task(struct pid *pid, enum pid_type type)
         struct task_struct *result = NULL;
         if (pid) {
                 struct hlist_node *first;
-                first = rcu_dereference_check(pid->tasks[type].first, rcu_read_lock_held() || lockdep_is_held(&tasklist_lock));
+                first = rcu_dereference_check(pid->tasks[type].first,
+                                              rcu_read_lock_held() ||
+                                              lockdep_tasklist_lock_is_held());
                 if (first)
                         result = hlist_entry(first, struct task_struct, pids[(type)].node);
         }
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 1439eb504c22..4a525a30e08e 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -246,12 +246,21 @@ struct rcu_data {
 
 #define RCU_JIFFIES_TILL_FORCE_QS        3      /* for rsp->jiffies_force_qs */
 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
-#define RCU_SECONDS_TILL_STALL_CHECK   (10 * HZ)  /* for rsp->jiffies_stall */
-#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ)  /* for rsp->jiffies_stall */
-#define RCU_STALL_RAT_DELAY             2         /* Allow other CPUs time */
-                                                  /*  to take at least one */
-                                                  /*  scheduling clock irq */
-                                                  /*  before ratting on them. */
+
+#ifdef CONFIG_PROVE_RCU
+#define RCU_STALL_DELAY_DELTA          (5 * HZ)
+#else
+#define RCU_STALL_DELAY_DELTA          0
+#endif
+
+#define RCU_SECONDS_TILL_STALL_CHECK   (10 * HZ + RCU_STALL_DELAY_DELTA)
+                                                /* for rsp->jiffies_stall */
+#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ + RCU_STALL_DELAY_DELTA)
+                                                /* for rsp->jiffies_stall */
+#define RCU_STALL_RAT_DELAY             2       /* Allow other CPUs time */
+                                                /*  to take at least one */
+                                                /*  scheduling clock irq */
+                                                /*  before ratting on them. */
 
 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
 
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 464ad2cdee00..79b53bda8943 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1010,6 +1010,10 @@ int rcu_needs_cpu(int cpu)
         int c = 0;
         int thatcpu;
 
+        /* Check for being in the holdoff period. */
+        if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies)
+                return rcu_needs_cpu_quick_check(cpu);
+
         /* Don't bother unless we are the last non-dyntick-idle CPU. */
         for_each_cpu_not(thatcpu, nohz_cpu_mask)
                 if (thatcpu != cpu) {
@@ -1041,10 +1045,8 @@ int rcu_needs_cpu(int cpu)
         }
 
         /* If RCU callbacks are still pending, RCU still needs this CPU. */
-        if (c) {
+        if (c)
                 raise_softirq(RCU_SOFTIRQ);
-                per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
-        }
         return c;
 }
 
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 3e1fd96c6cf9..5a5ea2cd924f 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -3476,7 +3476,7 @@ static void run_rebalance_domains(struct softirq_action *h)
 
 static inline int on_null_domain(int cpu)
 {
-        return !rcu_dereference(cpu_rq(cpu)->sd);
+        return !rcu_dereference_sched(cpu_rq(cpu)->sd);
 }
 
 /*
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index bb53edbb5c8c..d9062f5cc0c0 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -27,6 +27,7 @@
 #include <linux/ctype.h>
 #include <linux/list.h>
 #include <linux/hash.h>
+#include <linux/rcupdate.h>
 
 #include <trace/events/sched.h>
 
@@ -84,18 +85,22 @@ ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
 ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
 ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
 
+/*
+ * Traverse the ftrace_list, invoking all entries.  The reason that we
+ * can use rcu_dereference_raw() is that elements removed from this list
+ * are simply leaked, so there is no need to interact with a grace-period
+ * mechanism.  The rcu_dereference_raw() calls are needed to handle
+ * concurrent insertions into the ftrace_list.
+ *
+ * Silly Alpha and silly pointer-speculation compiler optimizations!
+ */
 static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
 {
-        struct ftrace_ops *op = ftrace_list;
-
-        /* in case someone actually ports this to alpha! */
-        read_barrier_depends();
+        struct ftrace_ops *op = rcu_dereference_raw(ftrace_list); /*see above*/
 
         while (op != &ftrace_list_end) {
-                /* silly alpha */
-                read_barrier_depends();
                 op->func(ip, parent_ip);
-                op = op->next;
+                op = rcu_dereference_raw(op->next); /*see above*/
         };
 }
 
@@ -150,8 +155,7 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
          * the ops->next pointer is valid before another CPU sees
          * the ops pointer included into the ftrace_list.
          */
-        smp_wmb();
-        ftrace_list = ops;
+        rcu_assign_pointer(ftrace_list, ops);
 
         if (ftrace_enabled) {
                 ftrace_func_t func;
diff --git a/kernel/trace/trace_event_profile.c b/kernel/trace/trace_event_profile.c
index f0d693005075..c1cc3ab633de 100644
--- a/kernel/trace/trace_event_profile.c
+++ b/kernel/trace/trace_event_profile.c
@@ -138,9 +138,9 @@ __kprobes void *ftrace_perf_buf_prepare(int size, unsigned short type,
         cpu = smp_processor_id();
 
         if (in_nmi())
-                trace_buf = rcu_dereference(perf_trace_buf_nmi);
+                trace_buf = rcu_dereference_sched(perf_trace_buf_nmi);
         else
-                trace_buf = rcu_dereference(perf_trace_buf);
+                trace_buf = rcu_dereference_sched(perf_trace_buf);
 
         if (!trace_buf)
                 goto err;