better-inode-locking.diff

diff --git a/runtime/print_flush.c b/runtime/print_flush.c
index 18b3e8f62..93535ba2c 100644
--- a/runtime/print_flush.c
+++ b/runtime/print_flush.c
@@ -111,6 +111,30 @@ void stp_print_flush(_stp_pbuf *pb)
                struct context* __restrict__ c = NULL;
                char *bufp = pb->buf;

+#if defined(__KERNEL__)
+               int locked;
+               struct rchan_buf *buf;
+               struct inode *inode;
+               int i;
+
+               buf = _stp_get_rchan_subbuf(_stp_relay_data.rchan->buf,
+                                           smp_processor_id());
+
+               inode = buf->dentry->d_inode;
+
+               if (in_interrupt() || in_atomic()) {
+                       locked = down_write_trylock(&inode->i_rwsem);
+                       if (unlikely(!locked)) {
+                               dbug_trans(0, "failed to obtain the relay file "
+                                          "inode lock");
+                               atomic_inc (&_stp_transport_failures);
+                       }
+               } else {
+                       inode_lock(inode);
+                       locked = 1;
+               }
+#endif  /* defined(__KERNEL__) */
+
                /* Prevent probe reentrancy on _stp_print_lock.
                 *
                 * Since stp_print_flush may be called from probe context, we
@@ -149,6 +173,11 @@ void stp_print_flush(_stp_pbuf *pb)
                }
                stp_spin_unlock_irqrestore(&_stp_print_lock, flags);
                _stp_runtime_entryfn_put_context(c);
+
+#if defined(__KERNEL__)
+               if (locked)
+                       up_write(&inode->i_rwsem);
+#endif
        }
 #endif /* STP_TRANSPORT_VERSION != 1 */
 #endif /* !STP_BULKMODE */