1 files changed, 17 insertions, 18 deletions

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 5fb1f2c87e6b..76aa04d4c925 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -35,7 +35,7 @@ unsigned long stack_trace_max_size;
 arch_spinlock_t stack_trace_max_lock =
         (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
 
-static DEFINE_PER_CPU(int, trace_active);
+DEFINE_PER_CPU(int, disable_stack_tracer);
 static DEFINE_MUTEX(stack_sysctl_mutex);
 
 int stack_tracer_enabled;
@@ -96,6 +96,14 @@ check_stack(unsigned long ip, unsigned long *stack)
         if (in_nmi())
                 return;
 
+        /*
+         * There's a slight chance that we are tracing inside the
+         * RCU infrastructure, and rcu_irq_enter() will not work
+         * as expected.
+         */
+        if (unlikely(rcu_irq_enter_disabled()))
+                return;
+
         local_irq_save(flags);
         arch_spin_lock(&stack_trace_max_lock);
 
@@ -207,13 +215,12 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip,
                  struct ftrace_ops *op, struct pt_regs *pt_regs)
 {
         unsigned long stack;
-        int cpu;
 
         preempt_disable_notrace();
 
-        cpu = raw_smp_processor_id();
         /* no atomic needed, we only modify this variable by this cpu */
-        if (per_cpu(trace_active, cpu)++ != 0)
+        __this_cpu_inc(disable_stack_tracer);
+        if (__this_cpu_read(disable_stack_tracer) != 1)
                 goto out;
 
         ip += MCOUNT_INSN_SIZE;
@@ -221,7 +228,7 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip,
         check_stack(ip, &stack);
 
  out:
-        per_cpu(trace_active, cpu)--;
+        __this_cpu_dec(disable_stack_tracer);
         /* prevent recursion in schedule */
         preempt_enable_notrace();
 }
@@ -253,7 +260,6 @@ stack_max_size_write(struct file *filp, const char __user *ubuf,
         long *ptr = filp->private_data;
         unsigned long val, flags;
         int ret;
-        int cpu;
 
         ret = kstrtoul_from_user(ubuf, count, 10, &val);
         if (ret)
@@ -264,16 +270,15 @@ stack_max_size_write(struct file *filp, const char __user *ubuf,
         /*
          * In case we trace inside arch_spin_lock() or after (NMI),
          * we will cause circular lock, so we also need to increase
-         * the percpu trace_active here.
+         * the percpu disable_stack_tracer here.
          */
-        cpu = smp_processor_id();
-        per_cpu(trace_active, cpu)++;
+        __this_cpu_inc(disable_stack_tracer);
 
         arch_spin_lock(&stack_trace_max_lock);
         *ptr = val;
         arch_spin_unlock(&stack_trace_max_lock);
 
-        per_cpu(trace_active, cpu)--;
+        __this_cpu_dec(disable_stack_tracer);
         local_irq_restore(flags);
 
         return count;
@@ -307,12 +312,9 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
 
 static void *t_start(struct seq_file *m, loff_t *pos)
 {
-        int cpu;
-
         local_irq_disable();
 
-        cpu = smp_processor_id();
-        per_cpu(trace_active, cpu)++;
+        __this_cpu_inc(disable_stack_tracer);
 
         arch_spin_lock(&stack_trace_max_lock);
 
@@ -324,12 +326,9 @@ static void *t_start(struct seq_file *m, loff_t *pos)
 
 static void t_stop(struct seq_file *m, void *p)
 {
-        int cpu;
-
         arch_spin_unlock(&stack_trace_max_lock);
 
-        cpu = smp_processor_id();
-        per_cpu(trace_active, cpu)--;
+        __this_cpu_dec(disable_stack_tracer);
 
         local_irq_enable();
 }