Commit-ID: 74e7ff8c50b6b022e6ffaa736b16a4dc161d3eaf
Gitweb: http://git.kernel.org/tip/74e7ff8c50b6b022e6ffaa736b16a4dc161d3eaf
Author: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
AuthorDate: Tue, 28 Jul 2009 20:17:22 +0800
Committer: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CommitDate: Tue, 28 Jul 2009 23:17:23 +0200
tracing: Fix missing function_graph events when we splice_read from trace_pipe
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@xxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxx
LKML-Reference: <4A6EEC52.90704@xxxxxxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
---
kernel/trace/trace.c | 10 +++++++---
1 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8bc8d8a..da984ad 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3085,7 +3085,8 @@ tracing_fill_pipe_page(size_t rem, struct trace_iterator *iter)
break;
}
- trace_consume(iter);
+ if (ret != TRACE_TYPE_NO_CONSUME)
+ trace_consume(iter);
rem -= count;
if (!find_next_entry_inc(iter)) {
rem = 0;
@@ -4233,8 +4234,11 @@ static void __ftrace_dump(bool disable_tracing)
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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