On Fri, 24 Jan 2025 16:41:38 +0100 Jiri Olsa <olsajiri@xxxxxxxxx> wrote: > On Fri, Jan 24, 2025 at 12:23:35PM +0100, Jiri Olsa wrote: > > On Thu, Jan 23, 2025 at 02:32:38PM -0800, Martin KaFai Lau wrote: > > > Hi Jiri, > > > > > > The "missed/kprobe_recursion" fails consistently on s390. It seems to start > > > failing after the recent bpf and bpf-next tree ffwd. > > > > > > An example: > > > https://github.com/kernel-patches/bpf/actions/runs/12934431612/job/36076956920 > > > > > > Can you help to take a look? > > > > > > afaict, it only happens on s390 so far, so cc IIya if there is any recent > > > change that may ring the bell. > > > > hi, > > I need to check more but I wonder it's the: > > 7495e179b478 s390/tracing: Enable HAVE_FTRACE_GRAPH_FUNC > > > > which seems to add recursion check and bail out before we have > > a chance to trigger it in bpf code > > so the test attaches bpf program test1 to bpf_fentry_test1 via kprobe.multi > > SEC("kprobe.multi/bpf_fentry_test1") > int test1(struct pt_regs *ctx) > { > bpf_kfunc_common_test(); > return 0; > } > > and several other programs are attached to bpf_kfunc_common_test function > > > I can't test this on s390, but looks like following is happening: > > kprobe.multi uses fprobe, so the test kernel path goes: > > bpf_fentry_test1 > ftrace_graph_func > function_graph_enter_regs > fprobe_entry > kprobe_multi_link_prog_run > test1 (bpf program) > bpf_kfunc_common_test > kprobe_ftrace_handler > kprobe_perf_func > trace_call_bpf > -> bpf_prog_active check fails, missed count is incremented > > > kprobe_ftrace_handler calls/takes ftrace_test_recursion_trylock (ftrace recursion lock) > > but s390 now calls/takes ftrace_test_recursion_trylock already in ftrace_graph_func, > so s390 stops at kprobe_ftrace_handler and does not get to trace_call_bpf to increment > prog->missed counters Oops, good catch! I missed to remove it from s390. We've already moved it in function_graph_enter_regs(). > > adding Sven, Masami, any idea? > > if the ftrace_test_recursion_trylock is needed ftrace_graph_func on s390, then > I think we will need to fix our test to skip s390 arch Yes. Please try this patch;
