Messages in this thread Patch in this message | | | Date | Thu, 13 Aug 2009 12:50:06 -0700 | From | Greg KH <> | Subject | [patch 31/74] tracing: Fix missing function_graph events when we splice_read from trace_pipe |
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2.6.30-stable review patch. If anyone has any objections, please let us know.
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From: Lai Jiangshan <laijs@cn.fujitsu.com>
commit 74e7ff8c50b6b022e6ffaa736b16a4dc161d3eaf upstream.
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: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <4A6EEC52.90704@cn.fujitsu.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- kernel/trace/trace.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
--- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2993,7 +2993,8 @@ tracing_fill_pipe_page(size_t rem, struc break; } - trace_consume(iter); + if (ret != TRACE_TYPE_NO_CONSUME) + trace_consume(iter); rem -= count; if (!find_next_entry_inc(iter)) { rem = 0; @@ -4122,8 +4123,11 @@ static void __ftrace_dump(bool disable_t iter.pos = -1; if (find_next_entry_inc(&iter) != NULL) { - print_trace_line(&iter); - trace_consume(&iter); + int ret; + + ret = print_trace_line(&iter); + if (ret != TRACE_TYPE_NO_CONSUME) + trace_consume(&iter); } trace_printk_seq(&iter.seq);
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