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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

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

Signed-off-by: Frederic Weisbecker <>
Cc: Steven Rostedt <>
LKML-Reference: <>
Signed-off-by: Ingo Molnar <>
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1 parent 07edf71 commit 7e6ea92df3fd7cbe74e7985c6f3e40255c44b201 @fweisbec fweisbec committed with Ingo Molnar Mar 22, 2009
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  1. +1 −0 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,
.selftest = trace_selftest_startup_nop,

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