• Lai Jiangshan's avatar
    tracing: Fix missing function_graph events when we splice_read from trace_pipe · 74e7ff8c
    Lai Jiangshan authored
    About a half events are missing when we splice_read
    from trace_pipe. They are unexpectedly consumed because we ignore
    the TRACE_TYPE_NO_CONSUME return value used by the function graph
    tracer when it needs to consume the events by itself to walk on
    the ring buffer.
    
    The same problem appears with ftrace_dump()
    
    Example of an output before this patch:
    
    1)               |      ktime_get_real() {
    1)   2.846 us    |          read_hpet();
    1)   4.558 us    |        }
    1)   6.195 us    |      }
    
    After this patch:
    
    0)               |      ktime_get_real() {
    0)               |        getnstimeofday() {
    0)   1.960 us    |          read_hpet();
    0)   3.597 us    |        }
    0)   5.196 us    |      }
    
    The fix also applies on 2.6.30
    Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: stable@kernel.org
    LKML-Reference: <4A6EEC52.90704@cn.fujitsu.com>
    Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    74e7ff8c
trace.c 98.1 KB