Hi Jiri, On Wed, 2 Feb 2022 01:02:43 +0100 Jiri Olsa <jolsa@xxxxxxxxxx> wrote: > On Mon, Jan 31, 2022 at 02:00:24PM +0900, Masami Hiramatsu wrote: > > Hi, > > > > Here is the 7th version of fprobe. This version fixes unregister_fprobe() > > ensures that exit_handler is not called after returning from the > > unregister_fprobe(), and fixes some comments and documents. > > > > The previous version is here[1]; > > > > [1] https://lore.kernel.org/all/164338031590.2429999.6203979005944292576.stgit@devnote2/T/#u > > > > This series introduces the fprobe, the function entry/exit probe > > with multiple probe point support. This also introduces the rethook > > for hooking function return as same as the kretprobe does. This > > abstraction will help us to generalize the fgraph tracer, > > because we can just switch to it from the rethook in fprobe, > > depending on the kernel configuration. > > > > The patch [1/10] is from Jiri's series[2]. > > > > [2] https://lore.kernel.org/all/20220104080943.113249-1-jolsa@xxxxxxxxxx/T/#u > > > > And the patch [9/10] adds the FPROBE_FL_KPROBE_SHARED flag for the case > > if user wants to share the same code (or share a same resource) on the > > fprobe and the kprobes. > > hi, > it works fine for bpf selftests, but when I use it through bpftrace > to attach more probes with: > > # ./src/bpftrace -e 'kprobe:ksys_* { }' > Attaching 27 probes > > I'm getting stalls like: > > krava33 login: [ 988.574069] INFO: task bpftrace:4137 blocked for more than 122 seconds. > [ 988.577577] Not tainted 5.16.0+ #89 > [ 988.580173] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 988.585538] task:bpftrace state:D stack: 0 pid: 4137 ppid: 4123 flags:0x00004004 > [ 988.589869] Call Trace: > [ 988.591312] <TASK> > [ 988.592577] __schedule+0x3a8/0xd30 > [ 988.594469] ? wait_for_completion+0x84/0x110 > [ 988.596753] schedule+0x4e/0xc0 > [ 988.598480] schedule_timeout+0xed/0x130 > [ 988.600524] ? rcu_read_lock_sched_held+0x12/0x70 > [ 988.602901] ? lock_release+0x253/0x4a0 > [ 988.604935] ? lock_acquired+0x1b7/0x410 > [ 988.607041] ? trace_hardirqs_on+0x1b/0xe0 > [ 988.609202] wait_for_completion+0xae/0x110 > [ 988.613762] __wait_rcu_gp+0x127/0x130 > [ 988.615787] synchronize_rcu_tasks_generic+0x46/0xa0 > [ 988.618329] ? call_rcu_tasks+0x20/0x20 > [ 988.620600] ? rcu_tasks_pregp_step+0x10/0x10 > [ 988.623232] ftrace_shutdown.part.0+0x174/0x210 > [ 988.625820] unregister_ftrace_function+0x37/0x60 > [ 988.628480] unregister_fprobe+0x2d/0x50 > [ 988.630928] bpf_link_free+0x4e/0x70 > [ 988.633126] bpf_link_release+0x11/0x20 > [ 988.635249] __fput+0xae/0x270 > [ 988.637022] task_work_run+0x5c/0xa0 > [ 988.639016] exit_to_user_mode_prepare+0x251/0x260 > [ 988.641294] syscall_exit_to_user_mode+0x16/0x50 > [ 988.646249] do_syscall_64+0x48/0x90 > [ 988.648218] entry_SYSCALL_64_after_hwframe+0x44/0xae > [ 988.650787] RIP: 0033:0x7f9079e95fbb > [ 988.652761] RSP: 002b:00007ffd474fa3b0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 > [ 988.656718] RAX: 0000000000000000 RBX: 00000000011bf8d0 RCX: 00007f9079e95fbb > [ 988.660110] RDX: 0000000000000000 RSI: 00007ffd474fa3b0 RDI: 0000000000000019 > [ 988.663512] RBP: 00007ffd474faaf0 R08: 0000000000000000 R09: 000000000000001a > [ 988.666673] R10: 0000000000000064 R11: 0000000000000293 R12: 0000000000000001 > [ 988.669770] R13: 00000000004a19a1 R14: 00007f9083428c00 R15: 00000000008c02d8 > [ 988.672601] </TASK> > [ 988.675763] INFO: lockdep is turned off. > > I have't investigated yet, any idea? Hmm, no, as far as I tested with my example module, it works well as below; # insmod fprobe_example.ko symbol='ksys_*' && ls && sleep 1 && rmmod fprobe_example.ko [ 125.820113] fprobe_init: Planted fprobe at ksys_* [ 125.823153] sample_entry_handler: Enter <ksys_write+0x0/0xf0> ip = 0x000000008d8da91f [ 125.824247] fprobe_handler.part.0+0xb1/0x150 [ 125.825024] fprobe_handler+0x1e/0x20 [ 125.825799] 0xffffffffa000e0e3 [ 125.826540] ksys_write+0x5/0xf0 [ 125.827344] do_syscall_64+0x3b/0x90 [ 125.828144] entry_SYSCALL_64_after_hwframe+0x44/0xae fprobe_example.ko [ 125.829178] sample_exit_handler: Return from <ksys_write+0x0/0xf0> ip = 0x000000008d8da91f to rip = 0x00000000be5e197e (__x64_sys_write+0x1a/0x20) [ 125.830707] fprobe_exit_handler+0x29/0x30 [ 125.831415] rethook_trampoline_handler+0x99/0x140 [ 125.832259] arch_rethook_trampoline_callback+0x3f/0x50 [ 125.833110] arch_rethook_trampoline+0x2f/0x50 [ 125.833803] __x64_sys_write+0x1a/0x20 [ 125.834448] do_syscall_64+0x3b/0x90 [ 125.835055] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 126.878825] fprobe_exit: fprobe at ksys_* unregistered # Even with NR_CPUS=3, it didn't cause the stall. But maybe you'd better test with Paul's fix as Andrii pointed. Thank you, > > thanks, > jirka > -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
