Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6

1 files changed, 24 insertions, 0 deletions

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 678a5120ee30..f4bc9b27de5f 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -157,6 +157,7 @@ stack_max_size_write(struct file *filp, const char __user *ubuf,
         unsigned long val, flags;
         char buf[64];
         int ret;
+        int cpu;
 
         if (count >= sizeof(buf))
                 return -EINVAL;
@@ -171,9 +172,20 @@ stack_max_size_write(struct file *filp, const char __user *ubuf,
                 return ret;
 
         local_irq_save(flags);
+
+        /*
+         * 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.
+         */
+        cpu = smp_processor_id();
+        per_cpu(trace_active, cpu)++;
+
         arch_spin_lock(&max_stack_lock);
         *ptr = val;
         arch_spin_unlock(&max_stack_lock);
+
+        per_cpu(trace_active, cpu)--;
         local_irq_restore(flags);
 
         return count;
@@ -206,7 +218,13 @@ 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)++;
+
         arch_spin_lock(&max_stack_lock);
 
         if (*pos == 0)
@@ -217,7 +235,13 @@ 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(&max_stack_lock);
+
+        cpu = smp_processor_id();
+        per_cpu(trace_active, cpu)--;
+
         local_irq_enable();
 }