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>

diff --git a/kernel/trace/trace_nop.c b/kernel/trace/trace_nop.c
index 9aa84bde23cd2d10e2207d635a908cc958286deb..394f94417e2f9edadbfdd449a90f5b8fd9ddd166 100644 (file)
--- 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