Messages in this thread | | | From | Ivan Babrou <> | Date | Fri, 12 Aug 2022 12:03:28 -0700 | Subject | Re: 5.15 ftrace bug when enabling function_graph |
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On Fri, Aug 5, 2022 at 3:25 PM Steven Rostedt <rostedt@goodmis.org> wrote: > > On Fri, 5 Aug 2022 13:14:47 -0700 > Ivan Babrou <ivan@cloudflare.com> wrote: > > > On Fri, Aug 5, 2022 at 11:53 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > > On Fri, 5 Aug 2022 11:37:56 -0700 > > > Ivan Babrou <ivan@cloudflare.com> wrote: > > > > > > > root@foo:~# echo 'bpf_dispatcher_*_func' > > > > > /sys/kernel/tracing/set_ftrace_notrace > > > > > > > > root@foo:~# trace-cmd record -p function_graph -l handle_mm_fault -P 3367417 > > > > plugin 'function_graph' > > > > Hit Ctrl^C to stop recording > > > > > > > > > > [1459709.204253] ------------[ ftrace bug ]------------ > > > > [1459709.204257] ftrace failed to modify > > > > [1459709.204262] [<ffffffffac3ea960>] bpf_dispatcher_xdp_func+0x0/0x10 > > > > [1459709.204275] actual: ffffffe9:ffffff9b:76:ffffffb0:14 > > > > [1459709.204302] Setting ftrace call site to call ftrace function > > > > [1459709.204305] ftrace record flags: 10000001 > > > > [1459709.204309] (1) > > > > expected tramp: ffffffffabc4bcb0 > > > > [1459709.204325] ------------[ cut here ]------------ > > > > > > Did you reboot since the error happened? Because the command you showed > > > should not have touched bpf_dispatcher_xdp_func. > > > > I did reboot, but I can reproduce if you have things for me to try. > > Let's see if this works manually. > > Reboot again. > > Make sure the above "ftrace bug" is not there. > > If not already mounted, as root: > > # mount -t tracefs tracefs /sys/krenel/tracing > # cd /sys/kernel/tracing > # cat enabled_functions > > Let me know what is there. > > # echo handle_mm_fault > set_ftrace_filter > # cat set_ftrace_filter > > to make sure that handle_mm_fault is listed. > > # echo function_graph > current_tracer > > If it fails again, let me know. It should not, but if it does, it needs to > be investigated.
It does not fail this way. It also doesn't fail when I run perf:
perf ftrace -N 'bpf_dispatcher_*_func' -G handle_mm_fault -a -- sleep 1
It does fail without "-N 'bpf_dispatcher_*_func'".
I suppose there's something about trace-cmd that makes it fail for me.
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