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authorSteven Rostedt <srostedt@redhat.com>2009-09-03 19:13:05 -0400
committerSteven Rostedt <rostedt@goodmis.org>2009-09-04 19:22:41 -0400
commite8165dbb03ed04d798163ee512074b9a9466a9c8 (patch)
treea9e640253a8ce14bada6a83fe1d85ecd74968695 /kernel
parent659372d3e42a3e17a2e042d38a8bcdb94bfbe797 (diff)
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.c13
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);