tracing/ftrace: make nop-tracer use polling wait for events on pipe

Impact: display events when they arrive

Now that the events don't use wake_up() anymore, we need the nop
tracer to poll waiting for events on the pipe. Especially because
nop is useful to look at orphan traces types (traces types that
don't rely on specific tracers) because it doesn't produce traces
itself.

And unlike other tracers that trigger specific traces periodically,
nop triggers no traces by itself that can wake him.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1237759847-21025-5-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 0 deletions

diff --git a/kernel/trace/trace_nop.c b/kernel/trace/trace_nop.c
index 9aa84bde23cd..394f94417e2f 100644
--- a/kernel/trace/trace_nop.c
+++ b/kernel/trace/trace_nop.c
@@ -91,6 +91,7 @@ struct tracer nop_trace __read_mostly =
         .name           = "nop",
         .init           = nop_trace_init,
         .reset          = nop_trace_reset,
+        .wait_pipe      = poll_wait_pipe,
 #ifdef CONFIG_FTRACE_SELFTEST
         .selftest       = trace_selftest_startup_nop,
 #endif