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From: John Kacur on 14 Jun 2010 18:30
From: Arnaldo Carvalho de Melo <acme(a)redhat.com>

The latency output showed:

# | task: -3 (uid:0 nice:0 policy:1 rt_prio:99)

The comm is missing in the "task:" and it looks like a minus 3 is
the output. The correct display should be:

# | task: migration/0-3 (uid:0 nice:0 policy:1 rt_prio:99)

The problem is that the comm is being stored in the wrong data
structure. The max_tr.data[cpu] is what stores the comm, not the
tr->data[cpu].

Before this patch the max_tr.data[cpu]->comm was zeroed and the /debug/trace
ended up showing just the '-' sign followed by the pid.

Also remove a needless initialization of max_data.

Signed-off-by: Arnaldo Carvalho de Melo <acme(a)redhat.com>
LKML-Reference: <1267824230-23861-1-git-send-email-acme(a)infradead.org>
Signed-off-by: Steven Rostedt <rostedt(a)goodmis.org>
Upstream commit: 1acaa1b2d9b5904c9cce06122990a2d71046ce16
Signed-off-by: John Kacur <jkacur(a)redhat.com>
---
kernel/trace/trace.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9b66ee1..a1cf0ad 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -520,7 +520,7 @@ static void
__update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
struct trace_array_cpu *data = tr->data[cpu];
- struct trace_array_cpu *max_data = tr->data[cpu];
+ struct trace_array_cpu *max_data;

max_tr.cpu = cpu;
max_tr.time_start = data->preempt_timestamp;
@@ -530,7 +530,7 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
max_data->critical_start = data->critical_start;
max_data->critical_end = data->critical_end;

- memcpy(data->comm, tsk->comm, TASK_COMM_LEN);
+ memcpy(max_data->comm, tsk->comm, TASK_COMM_LEN);
max_data->pid = tsk->pid;
max_data->uid = task_uid(tsk);
max_data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;
--
1.6.6.1

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Prev: [PATCH 6/6] hvc_console: Fix race between hvc_close and hvc_remove
Next: [PATCH 2/6: v4] lockdep: Make MAX_STACK_TRACE_ENTRIES configurable.