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SubjectRe: [PATCH v2] tracing/function-graph-tracer: prevent from hrtimer interrupt infinite loop
2008/12/21 Ingo Molnar <mingo@elte.hu>:
>
> btw., a graph-tracer buglet i noticed:
>
> 3) | perf_counter_task_tick() {
> 3) | perf_counter_task_sched_out() {
> 3) | /* c:ffff88049b184000, u:0: 0000000020ca1ab0 + 0000000000000000 = 0000000020ca1ab0
> */
> 3) | /* sched-out counter ffff88049b184000, state: 0
> */
> 3) 5.024 us | }
> 3) | perf_counter_task_sched_in() {
> 3) | /* c:ffff88049b184000, u:0: 0000000020ca1ab0 + 0000000000000000 = 0000000020ca1ab0
> */
> 3) | /* sched-in counter ffff88049b184000, state: 1
> */
> 3) 2.605 us | }
> 3) 9.714 us | }
> 3) | perf_counter_task_tick() {
>
> the bug is that the '*/' comment closing text is printed in the next line
> - that's not a linewrap, it happened like this in the trace.
>
> The reason is that the ftrace_printk did:
>
> ftrace_printk("c:%p, u:%d: %016Lx + %016Lx = %016Lx\n",
>
> the closing \n is pretty natural - especially for kernel hackers who might
> just turn printk()s into ftrace_printk(), to embedd printouts in function
> traces. So it would be nice if ftrace skipped over \n's when printing them
> out as embedded C comments.
>
> Ingo
>


Yes I was afraid of the \n from the user for these comments. You're
right, I will skip the newlines
from the user.


2008/12/21 Ingo Molnar <mingo@elte.hu>:
>
> * Ingo Molnar <mingo@elte.hu> wrote:
>
>> btw., a graph-tracer buglet i noticed:
>
> another thing. I turned off all the options that come ahead of the 'meat'
> of the trace data:
>
> # cat /debug/tracing/trace_options
> print-parent nosym-offset nosym-addr noverbose noraw nohex nobin noblock
> nostacktrace nosched-tree ftrace_printk noftrace_preempt nobranch annotate
> nouserstacktrace nosym-userobj printk-msg-only nofuncgraph-overrun
> nofuncgraph-cpu nofuncgraph-overhead nofuncgraph-proc
>
> but i still got the 'duration' field printed:
>
> # tracer: function_graph
> #
> # DURATION FUNCTION CALLS
> # | | | | |
>
> 0.865 us | }
> | alloc_page_vma() {
> 0.295 us | get_vma_policy();
> 0.268 us | policy_zonelist();
> | __alloc_pages_internal() {
> 0.257 us | __might_sleep();
> | get_page_from_freelist() {
>
>
> i'd have expected to only see the flow of execution as it happens.
>
> Ingo
>


Strange. I will test that.


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