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author | Steven Rostedt <srostedt@redhat.com> | 2009-09-04 01:13:05 +0200 |
---|---|---|
committer | Steven Rostedt <rostedt@goodmis.org> | 2009-09-05 01:22:41 +0200 |
commit | e8165dbb03ed04d798163ee512074b9a9466a9c8 (patch) | |
tree | a9e640253a8ce14bada6a83fe1d85ecd74968695 /kernel | |
parent | tracing: add trace_array_printk for internal tracers to use (diff) | |
download | linux-e8165dbb03ed04d798163ee512074b9a9466a9c8.tar.xz linux-e8165dbb03ed04d798163ee512074b9a9466a9c8.zip |
tracing: report error in trace if we fail to swap latency buffer
The irqsoff tracer will fail to swap the cpu buffer with the max
buffer if it preempts a commit. Instead of ignoring this, this patch
makes the tracer report it if the last max latency failed due to preempting
a current commit.
The output of the latency tracer will look like this:
# tracer: irqsoff
#
# irqsoff latency trace v1.1.5 on 2.6.31-rc5
# --------------------------------------------------------------------
# latency: 112 us, #1/1, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:4)
# -----------------
# | task: -4281 (uid:0 nice:0 policy:0 rt_prio:0)
# -----------------
# => started at: save_args
# => ended at: __do_softirq
#
#
# _------=> CPU#
# / _-----=> irqs-off
# | / _----=> need-resched
# || / _---=> hardirq/softirq
# ||| / _--=> preempt-depth
# |||| /
# ||||| delay
# cmd pid ||||| time | caller
# \ / ||||| \ | /
bash-4281 1d.s6 265us : update_max_tr_single: Failed to swap buffers due to commit in progress
Note the latency time and the functions that disabled the irqs or preemption
will still be listed.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/trace/trace.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index ef08328eb28d..6df9861fde6b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -482,9 +482,20 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu) ret = ring_buffer_swap_cpu(max_tr.buffer, tr->buffer, cpu); + if (ret == -EBUSY) { + /* + * We failed to swap the buffer due to a commit taking + * place on this CPU. We fail to record, but we reset + * the max trace buffer (no one writes directly to it) + * and flag that it failed. + */ + trace_array_printk(&max_tr, _THIS_IP_, + "Failed to swap buffers due to commit in progress\n"); + } + ftrace_enable_cpu(); - WARN_ON_ONCE(ret && ret != -EAGAIN); + WARN_ON_ONCE(ret && ret != -EAGAIN && ret != -EBUSY); __update_max_tr(tr, tsk, cpu); __raw_spin_unlock(&ftrace_max_lock); |