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  • Frederic Weisbecker's avatar
    tracing/core: use appropriate waiting on trace_pipe · 6eaaa5d5
    Frederic Weisbecker authored
    Impact: api and pipe waiting change
    Currently, the waiting used in tracing_read_pipe() is done through a
    100 msecs schedule_timeout() loop which periodically check if there
    are traces on the buffer.
    This can cause small latencies for programs which are reading the incoming
    This patch makes the reader waiting for the trace_wait waitqueue except
    for few tracers such as the sched and functions tracers which might be
    already hold the runqueue lock while waking up the reader.
    This is performed through a new callback wait_pipe() on struct tracer.
    If none is implemented on a specific tracer, the default waiting for
    trace_wait queue is attached.
    Signed-off-by: default avatarFrederic Weisbecker <>
    Signed-off-by: default avatarIngo Molnar <>