On Sun, Jan 26, 2025 at 2:06 PM Jiri Olsa <olsajiri@xxxxxxxxx> wrote: > > On Sun, Jan 26, 2025 at 11:40:05PM +0900, Masami Hiramatsu wrote: > > 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; > > > > > > From 12fcda79d0b1082449d5f7cfb8039b0237cf246d Mon Sep 17 00:00:00 2001 > > From: "Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx> > > Date: Sun, 26 Jan 2025 23:38:59 +0900 > > Subject: [PATCH] s390: fgraph: Fix to remove ftrace_test_recursion_trylock() > > > > Fix to remove ftrace_test_recursion_trylock() from ftrace_graph_func() > > because commit d576aec24df9 ("fgraph: Get ftrace recursion lock in > > function_graph_enter") has been moved it to function_graph_enter_regs() > > already. > > > > Reported-by: Jiri Olsa <olsajiri@xxxxxxxxx> > > Fixes: d576aec24df9 ("fgraph: Get ftrace recursion lock in function_graph_enter") > > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> > > great, ci is passing with this fix > > Tested-by: Jiri Olsa <jolsa@xxxxxxxxxx> Masami, Are you going to land this fix in your tree? We can create a temporary patch for BPF CI once you have the commit in the tree. > > thanks, > jirka > > > > --- > > arch/s390/kernel/ftrace.c | 5 ----- > > 1 file changed, 5 deletions(-) > > > > diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c > > index c0b2c97efefb..63ba6306632e 100644 > > --- a/arch/s390/kernel/ftrace.c > > +++ b/arch/s390/kernel/ftrace.c > > @@ -266,18 +266,13 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, > > struct ftrace_ops *op, struct ftrace_regs *fregs) > > { > > unsigned long *parent = &arch_ftrace_regs(fregs)->regs.gprs[14]; > > - int bit; > > > > if (unlikely(ftrace_graph_is_dead())) > > return; > > if (unlikely(atomic_read(¤t->tracing_graph_pause))) > > return; > > - bit = ftrace_test_recursion_trylock(ip, *parent); > > - if (bit < 0) > > - return; > > if (!function_graph_enter_regs(*parent, ip, 0, parent, fregs)) > > *parent = (unsigned long)&return_to_handler; > > - ftrace_test_recursion_unlock(bit); > > } > > > > #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ > > -- > > 2.43.0 > > > > Thank you, > > > > -- > > Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> >
