TRACE(): facilitate debugging

- don't deadlock on a runqueue lock in case of a bug inside
  the scheduler
- write printk() messages to TRACE()
- tell user of TRACE() buffer

1 files changed, 30 insertions, 2 deletions

diff --git a/litmus/sched_trace.c b/litmus/sched_trace.c
index 0976e830ad..43447851da 100644
--- a/litmus/sched_trace.c
+++ b/litmus/sched_trace.c
@@ -373,6 +373,9 @@ static int trace_open(struct inode *in, struct file *filp)
         return error;
 }
 
+
+extern int trace_override;
+
 /* log_open - open the global log message ring buffer.
  */
 static int log_open(struct inode *in, struct file *filp)
@@ -398,13 +401,38 @@ static int log_open(struct inode *in, struct file *filp)
 
         error = 0;
         filp->private_data = buf;
-
+        printk(KERN_DEBUG "sched_trace buf: from 0x%p to 0x%p  length: %lx\n",
+               buf->buf.buf, buf->buf.end, buf->buf.end - buf->buf.buf);
+        trace_override++;
  out_unlock:
         up(&buf->reader_mutex);
  out:
         return error;
 }
 
+static int log_release(struct inode *in, struct file *filp)
+{
+        int error               = -EINVAL;
+        trace_buffer_t* buf     = filp->private_data;
+
+        BUG_ON(!filp->private_data);
+
+        if (down_interruptible(&buf->reader_mutex)) {
+                error = -ERESTARTSYS;
+                goto out;
+        }
+
+        /*      last release must deallocate buffers    */
+        if (atomic_dec_return(&buf->reader_cnt) == 0) {
+                error = rb_free_buf(&buf->buf);
+        }
+
+        trace_override--;
+        up(&buf->reader_mutex);
+ out:
+        return error;
+}
+
 /******************************************************************************/
 /*                          Device Registration                               */
 /******************************************************************************/
@@ -434,7 +462,7 @@ struct file_operations trace_fops = {
 struct file_operations log_fops = {
         .owner   = THIS_MODULE,
         .open    = log_open,
-        .release = trace_release,
+        .release = log_release,
         .read    = trace_read,
 };