[PATCH][GIT PULL][v3.4] tracing: Fix ent_size in trace output

From: Steven Rostedt
Date: Tue Mar 27 2012 - 13:25:21 EST


Please pull the latest tip/perf/urgent tree, which can be found at:


Head SHA1: 12b5da349a8b94c9dbc3430a6bc42eabd9eaf50b

Steven Rostedt (1):
tracing: Fix ent_size in trace output

kernel/trace/trace.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
commit 12b5da349a8b94c9dbc3430a6bc42eabd9eaf50b
Author: Steven Rostedt <srostedt@xxxxxxxxxx>
Date: Tue Mar 27 10:43:28 2012 -0400

tracing: Fix ent_size in trace output

When reading the trace file, the records of each of the per_cpu buffers
are examined to find the next event to print out. At the point of looking
at the event, the size of the event is recorded. But if the first event is
chosen, the other events in the other CPU buffers will reset the event size
that is stored in the iterator descriptor, causing the event size passed to
the output functions to be incorrect.

In most cases this is not a problem, but for the case of stack traces, it
is. With the change to the stack tracing to record a dynamic number of
back traces, the output depends on the size of the entry instead of the
fixed 8 back traces. When the entry size is not correct, the back traces
would not be fully printed.

Note, reading from the per-cpu trace files were not affected.

Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 3a19c35..ed7b5d1 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1698,6 +1698,7 @@ __find_next_entry(struct trace_iterator *iter, int *ent_cpu,
int cpu_file = iter->cpu_file;
u64 next_ts = 0, ts;
int next_cpu = -1;
+ int next_size = 0;
int cpu;

@@ -1729,9 +1730,12 @@ __find_next_entry(struct trace_iterator *iter, int *ent_cpu,
next_cpu = cpu;
next_ts = ts;
next_lost = lost_events;
+ next_size = iter->ent_size;

+ iter->ent_size = next_size;
if (ent_cpu)
*ent_cpu = next_cpu;

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